Copyright(C) 1994,1995,1996,1997 Terumasa KODAKA , Takeshi KONO
[0000:0000h〜0000:03FFh : Interrupt Vector]
+00 +04 +08 +0C +10 +14 +18 +1C
0000 INT 00 | INT 01 | INT 02 | INT 03 | INT 04 | INT 05 | INT 06 | INT 07 |
0020 INT 08 | INT 09 | INT 0A | INT 0B | INT 0C | INT 0D | INT 0E | INT 0F |
0040 INT 10 | INT 11 | INT 12 | INT 13 | INT 14 | INT 15 | INT 16 | INT 17 |
0060 INT 18 | INT 19 | INT 1A | INT 1B | INT 1C | INT 1D | INT 1E | INT 1F |
0080 INT 20 | INT 21 | INT 22 | INT 23 | INT 24 | INT 25 | INT 26 | INT 27 |
00A0 INT 28 | INT 29 | INT 2A | INT 2B | INT 2C | INT 2D | INT 2E | INT 2F |
00C0 INT 30 | INT 31 | INT 32 | INT 33 | INT 34 | INT 35 | INT 36 | INT 37 |
00E0 INT 38 | INT 39 | INT 3A | INT 3B | INT 3C | INT 3D | INT 3E | INT 3F |
0100 INT 40 | INT 41 | INT 42 | INT 43 | INT 44 | INT 45 | INT 46 | INT 47 |
0120 INT 48 | INT 49 | INT 4A | INT 4B | INT 4C | INT 4D | INT 4E | INT 4F |
0140 INT 50 | INT 51 | INT 52 | INT 53 | INT 54 | INT 55 | INT 56 | INT 57 |
0160 INT 58 | INT 59 | INT 5A | INT 5B | INT 5C | INT 5D | INT 5E | INT 5F |
0180 INT 60 | INT 61 | INT 62 | INT 63 | INT 64 | INT 65 | INT 66 | INT 67 |
01A0 INT 68 | INT 69 | INT 6A | INT 6B | INT 6C | INT 6D | INT 6E | INT 6F |
01C0 INT 70 | INT 71 | INT 72 | INT 73 | INT 74 | INT 75 | INT 76 | INT 77 |
01E0 INT 78 | INT 79 | INT 7A | INT 7B | INT 7C | INT 7D | INT 7E | INT 7F |
0200 INT 80 | INT 81 | INT 82 | INT 83 | INT 84 | INT 85 | INT 86 | INT 87 |
0220 INT 88 | INT 89 | INT 8A | INT 8B | INT 8C | INT 8D | INT 8E | INT 8F |
0240 INT 90 | INT 91 | INT 92 | INT 93 | INT 94 | INT 95 | INT 96 | INT 97 |
0260 INT 98 | INT 99 | INT 9A | INT 9B | INT 9C | INT 9D | INT 9E | INT 9F |
0280 INT A0 | INT A1 | INT A2 | INT A3 | INT A4 | INT A5 | INT A6 | INT A7 |
02A0 INT A8 | INT A9 | INT AA | INT AB | INT AC | INT AD | INT AE | INT AF |
02C0 INT B0 | INT B1 | INT B2 | INT B3 | INT B4 | INT B5 | INT B6 | INT B7 |
02E0 INT B8 | INT B9 | INT BA | INT BB | INT BC | INT BD | INT BE | INT BF |
0300 INT C0 | INT C1 | INT C2 | INT C3 | INT C4 | INT C5 | INT C6 | INT C7 |
0320 INT C8 | INT C9 | INT CA | INT CB | INT CC | INT CD | INT CE | INT CF |
0340 INT D0 | INT D1 | INT D2 | INT D3 | INT D4 | INT D5 | INT D6 | INT D7 |
0360 INT D8 | INT D9 | INT DA | INT DB | INT DC | INT DD | INT DE | INT DF |
0380 INT E0 | INT E1 | INT E2 | INT E3 | INT E4 | INT E5 | INT E6 | INT E7 |
03A0 INT E8 | INT E9 | INT EA | INT EB | INT EC | INT ED | INT EE | INT EF |
03C0 INT F0 | INT F1 | INT F2 | INT F3 | INT F4 | INT F5 | INT F6 | INT F7 |
03E0 INT F8 | INT F9 | INT FA | INT FB | INT FC | INT FD | INT FE | INT FF |
[0000:0400h〜0000:05FFh : System-wide area]
-------------------------------------------------------------------------------
Memory 0000:0400h
Type 8bit FLAGS
Name BIOS_FLAG2
・bit 7
Classification Model discrimination
Target All models (except PC-98HA, DB-P1)
Content Presence or absence of RAM drive function
1 = RAM drive function present
0 = No RAM drive function
Explanation u Some technical data books state that this is a 98NOTE discrimination,
but in fact it indicates the presence or absence of a RAM drive function.
o PC-9801NL/R does not have a RAM drive function, so it is 0. PC-9801UR,
which is a desktop type but has a RAM drive function, is 1.
u PC-98HA, DB-P1 have a RAM drive function, but this bit is 0.
o Even if you set "RAM drive not used", this bit remains 1.
Whether or not a RAM drive is set is indicated in 0000:0488h.
Related 0000:0488h
・bit 6
Classification
Target
Content Unused(?)
Explanation
Related
・bit 5
Classification RESUME
Undocumented
Target 98NOTE (except PC-9801N/NS), PC-98HA
Content Resume function ON/OFF status
1 = Resume (ON)
0 = Do not resume (OFF)
Explanation o Indicates the ON/OFF status of the resume function. Overwriting this bit does
not change the setting status of the resume function in the 98NOTE/HANDY98 menu.
u When the resume function is switched ON/OFF in the 98NOTE/HANDY98 menu or when
the power is turned ON, the menu setting is copied to this bit. When the power
switch is pressed or [CTRL]+[GRPH]+[HELP] is pressed, the resume operation is
determined according to the status of this bit, not the menu setting.
Related INT 1Fh - Function 98h
・bit 4
Classification RESUME
Target PC-9801NV･NS/E･NC･NL･NS/L･NA･NA/C, PC-98HA
Contents Resume/suspend notification by INT 1Fh - Function 8B,8Ch
1 = Notify
0 = Do not notify
Explanation o When this bit is set to 1, an interrupt occurs to notify when the power is
turned ON/OFF with resume ON.
o When the power is turned OFF, a suspend processing interrupt INT 1Fh - Function 8C00h
(Function 8Ch for PC-98HA) occurs. When the power is turned ON, a resume processing
interrupt INT 1Fh - Function 8B00h (Function 8Bh for PC-98HA) occurs. Software that
requires suspend and resume processing can hook the above functions of INT 1Fh and
set this bit to 1 to perform the necessary processing.
Related INT 1Fh - Function 8B00h
INT 1Fh - Function 8B80h
INT 1Fh - Function 8Bh
INT 1Fh - Function 8C00h
INT 1Fh - Function 8C80h
INT 1Fh - Function 8Ch
・bit 3
Classification CPU identification
Target All models
Content V33A identification
1 = V33A
0 = Other
Explanation o PC-98DO+ is the only model equipped with V33A. Always 0 for other models.
Related 0000:0480h bit 1,0
0000:0484h bit 3〜0
0000:0501h bit 6
・bit 2
Classification CPU speed
Undocumented
Target PC-9801RA21 and later models
Content Middle mode display
-----------------+---------------+-------------
Model name | bit 2=1 | bit 2=0
-----------------+---------------+-------------
PC-9801RA21 | 386 16MHz | 386 20MHz,V30
PC-9801DA2 | Middle | High/Low
PC-9821Ce | Middle | High/Low
PC-9801NA | Middle | High/Low
PC-9821Ne | Middle | High/Low
PC-9801NX/C | Middle | High/Low
PC-9801NS/A | Middle | High/Low
-----------------+---------------+-------------
Explanation o Details unknown. It is set to 1 only in Middle mode on the models listed in
the table. It is always set to 0 on other models.
Related
・bit 1
Classification Undocumented
Target PC-9801RA2 and later models
Content Unknown
Models that are always 1:
PC-9801CV･N･NC･NS/E･NS/T･NS/L･NS/R･NX/C･P･NL/R, PC-9821Ne, PC-98HA, DB-P1
Models that are always 0:
PC-9801UV11･UR･UF･T･RX2･RX21･DX･FS･FX･BA･BX･LS･NV･NL, PC-H98 model60･70･90･100･105,
PC-H98S, PC-98GS, PC-98LT
Models that change depending on CPU speed (0 in Low mode, 1 otherwise):
PC-9801ES･RA21･RS･DA･DS･FA･US･BA2･BS2･BX2･NA･NS/A, PC-9821 original, Ap, As, Ae, Af,
Ap2, As2, An, Bp, Bs, Be, Bf, Ce
Models that change depending on CPU speed (1 in Middle mode, 0 otherwise):
PC-H98 model80, PC-98RL
* Both normal and high-resolution modes
Models that change depending on CPU speed (0 in High mode, 1 in Low mode):
PC-9801NS
Explanation o Details unknown. Depending on the model and mode, the state will be as listed in the table.
Related
・bit 0
Classification BRANCH BIOS
Undocumented
Target PC-9864 first generation/U (Hi-Res excluding PC-H98)
Content Presence or absence of BRANCH 4670 I/F
1 = Yes
0 = No
Explanation o When PC-9864/U (BRANCH 4670 I/F board) is implemented in Hi-Res mode (excluding PC-H98),
if BRANCH BIOS is available, it becomes 1.
o In normal mode, it is 0 even when BRANCH BIOS is built in.
Related 0000:041E-0443h
0000:0480h bit 5
0000:05E5h
Memory 0000:0401h
Type BYTE
Name EXPMMSZ
Classification MEMORY
Undocumented
Target CPUs with 80286 or higher
Contents Usable protected mode memory capacity within 16MB (unit: 128KB)
Explanation o Indicates the amount of usable protected mode memory located at 100000 (1M) to FFFFFFh (16M-1).
u Also serves as a resource management work area for HIMEM.SYS, RAMDISK.SYS, EMM.SYS, etc.
When using protected memory, the necessary amount of memory is allocated from the higher addresses.
Then, this value is reduced by the amount equivalent to that memory capacity. In this way, protected
mode memory can be used by multiple drivers. After these drivers are installed, it will no longer
indicate the physical memory capacity. The maximum value of this byte is 70h (14MB). This is to
exclude real mode memory space (000000-0FFFFFh) and the 16MB system space (F00000-FFFFFFh).
However, the maximum value is 78h (15MB) only when "Do not use 16MB system space" is set in the
system setup menu of a machine capable of installing more than 16MB of memory.
o The capacity of memory located at addresses 00000-9FFFFh (normal mode) / 00000-BFFFFh (high
resolution mode) is stored in 0000:0501h bits 2-0.
o On the PC-H98 and machines capable of installing more than 16MB of memory, the capacity of memory
located at addresses 1000000h (16MB) and above is stored in 0000:0594h.
Related 0000:0501h bit 2-0
0000:0594h
INT DC - Function 81h
INT DC - Function 82h
Memory 0000:0402h
Type BYTE
Name SYS_SEL
Classification DISK
Undocumented
Target Hi-Res
Contents Selector number
bit 7: [SHIFT] key pressed state at startup
1 = ON
0 = OFF
bit 6: [CTRL] key pressed state at startup (1/0 meaning is opposite to bits 7 and 5)
1 = OFF
0 = ON
bit 5: [GRPH] key pressed state at startup
1 = ON
0 = OFF
bit 4-0: Selector number (00-1Fh)
Explanation o Bits 4-0 are the selector number to indicate which partition on the hard disk to boot from.
The boot loader at the top of the hard disk refers to the selector number to determine which
partition on the hard disk to boot the OS from. If a value other than 0 is stored in the
selector number, the connected hard disk is searched for a partition with that selector
number and the OS is booted. When the selector number is 0, the hard disk boot menu is displayed.
u Bits 7 and 6 are cleared inside the BIOS during boot processing, so they always show 0 after
the OS starts. Bit 5 shows 1 after the OS starts if the [GRPH] key is pressed at boot.
u Before the disk boot process, copy the values of memory switch 5
bits 7-4 to 0000:0402h
bits 7-4, and memory switch 6 bits 7-4 to 0000:0402h bits 3-0.
u If a specific key is pressed at reset, the memory switch selector number and the shift key
pressing state at boot will change. The memory switch is rewritten when a key shown in the
table [How to set the selector number] or [SHIFT], [CTRL], or [GRPH] is pressed.
The memory switch is not rewritten even if other keys are pressed alone.
If you reset while pressing a key shown in table [How to set the selector number], the state
of the shift keys pressed at that time will be reflected in memory switch 5.
Similarly, when you reset while pressing [SHIFT], [CTRL], or [GRPH], if a key shown in table
[How to set the selector number] is not pressed, the selector number of memory switch 6
will be set to 00h.
Table How to set the selector number
--------------------+-----------------------------+-----------------+----------------------------------
Selector number | Key to press when resetting | Selector number | Key to press when resetting
--------------------+-----------------------------+-----------------+----------------------------------
00h | [ESC] or [@] | 10h | [P]
01h | [f･1] or [A] | 11h | [Q]
02h | [f･2] or [B] | 12h | [R]
03h | [f･3] or [C] | 13h | [S]
04h | [f･4] or [D] | 14h | [T]
05h | [f･5] or [E] | 15h | [U]
06h | [f･6] or [F] | 16h | [V]
07h | [f･7] or [G] | 17h | [W]
08h | [f･8] or [H] | 18h | [X]
09h | [f･9] or [I] | 19h | [Y]
0Ah | [f･10] or [J] | 1Ah | [Z]
0Bh | [vf･1] or [K] | 1Bh | [[]
0Ch | [vf･2] or [L] | 1Ch | [¥]
0Dh | [vf･3] or [M] | 1Dh | []]
0Eh | [vf･4] or [N] | 1Eh | [^]
0Fh | [vf･5] or [O] | 1Fh | [_]
--------------------+-----------------------------+-----------------+----------------------------------
Related Memory switch 5 bits 7-4
Memory switch 6 bits 7-4
Hard disk partition table structure
Memory 0000:0402h
Type BYTE
Name
Classification ITF
Undocumented
Target PC-9801RA2 or later models with ITF (normal)
Contents [SHIFT], [CTRL], [GRPH] key status when reset
Explanation o If the [SHIFT], [CTRL], or [GRPH] key is pressed when resetting, the corresponding bit becomes 1.
Unlike high resolution, it is not recorded in the memory switch.
bit 7: SHIFT key pressed status
1 = ON
0 = OFF
bit 6: CTRL key pressed status
1 = ON
0 = OFF
bit 5: GRPH key pressed status
1 = ON
0 = OFF
bit 4-0: Always 0 (unused)
Related
Memory 0000:0402h (LT/HA)
Type WORD
Name
Classification LCD
Undocumented
Target PC-98LT/HA, DB-P1
Contents Error message display position at system startup
Explanation o Each time an error message is output, the value of this address is incremented to move the next
display position down.
Related
Memory 0000:0403h
Type BYTE
Name ITF_WORK
Classification ITF
Undocumented
Target Models with ITF ROM
Contents Work area during ITF ROM execution
Explanation
Related
Memory 0000:0404-0407h
Type DWORD
Name USER_SP, USER_SS
Classification CPU
Undocumented
Target 80286 or later CPU equipped machines, PC-9801VM21
Content Stack pointer save location at shutdown
Explanation o Since the 80286 cannot return from protected mode to real mode by software, it is necessary to
return to real mode using external hardware that resets only the CPU. This address is used to
save the stack pointer at that time.
o On models equipped with 80286 or later CPUs, if the SHUT 0 bit of the system port is 0, shutting
down (OUT 00F0h) will return to real mode. After resetting, the CPU checks the SHUT 0 bit when
executing the ITF ROM, and if it is 0, sets the stack pointer as SP←0000:0404h, SS←0000:0406h,
and executes RETF. Before shutting down, the program that performs the shutdown should push the
necessary registers and the FAR address to restart after reset.
Related I/O 0035h (SHUT mode setting system port)
I/O 00F0h (shutdown port)
Memory 0000:0408h
Type BYTE
Name
Classification LCD
Undocumented
Target PC-98HA
Contents Resume state save (LCD)
Explanation o Area for saving the value output to I/O 0810h when OUT 0812h,00h.
Related I/O 0810h
I/O 0812h
Memory 0000:0409h
Type BYTE
Name
Classification LCD
Undocumented
Target PC-98HA
Contents Resume state save (LCD)
Explanation o Area for saving the value output to I/O 0810h when OUT 0812h,01h.
Related I/O 0810h
I/O 0812h
Memory 0000:040Ah (LT/HA)
Type WORD
Name
Classification LCD
Undocumented
Target PC-98LT/HA, DB-P1
Contents Unknown
Explanation
Related
Memory 0000:040C-040Fh (LT/HA)
Type 4 BYTES
Name
Classification
Target PC-98LT/HA, DB-P1
Contents
Explanation Unused
Related
Memory 0000:0410-0417h (HA)
Type 8 BYTES
Name NO NAME
Category RESUME
Target PC-98HA
Contents Resume state save (EMS)
0410h I/O Value output to 08E9h (C000h SEL PKG)
0411h I/O Value output to 08E1h (C000h SEL BANK)
0412h I/O Value output to 08E9h (C400h SEL PKG)
0413h I/O Value output to 08E3h (C400h SEL BANK)
0414h I/O Value output to 08E9h (C800h SEL PKG)
0415h I/O Value output to 08E5h (C800h SEL BANK)
0416h I/O Value output to 08E9h (CC00h SEL PKG)
0417h I/O Value output to 08E7h (CC00h SEL BANK)
Explanation o Area for saving values output to the I/O port for controlling the EMS card.
u This work area is used only by PC-98HA. In 98NOTE, the RESUME BIOS saves the data in the
RESUME work area in bank RAM, so the system common area is not used.
Related I/O 08E1h
I/O 08E3h
I/O 08E5h
I/O 08E7h
I/O 08E9h
Memory 0000:0408-040Fh
Type 8 BYTES
Name KB_SHIFT_CODE
Category KEYBOARD BIOS
Target Hi-Res
Contents Shift key code table
--------+-----------------------------+------------------------
Address | Bit position of shift state | Initial memory contents
--------+-----------------------------+------------------------
0408h | bit 7 | FFh
0409h | bit 6 | FFh
040Ah | bit 5 | FFh
040Bh | bit 4 | 74h([CTRL])
040Ch | bit 3 | 73h([GRPH])
040Dh | bit 2 | 72h([Kana])
040Eh | bit 1 | 71h([CAPS])
040Fh | bit 0 | 70h([SHIFT])
--------+-----------------------------+------------------------
Explanation o A table that defines shift keys. In high-resolution mode, shift keys can be redefined to any key.
The table stores the key numbers of the keys defined as shift keys.
o Up to eight shift keys can be defined, but it is generally used to redefine the key numbers of
the [CTRL], [GRPH], [Kana], [CAPS], and [SHIFT] keys. For example, if you set a key number to 040Fh,
the keyboard BIOS will recognize that key as the [SHIFT] key. When the contents of the table are
changed, it is reflected in the shift states such as 0000:053Ah (shift key pressed state flag),
INT 18h - Function 02h, and key data values such as INT 18h - Function 00h.
o The pressed state table for keys from 0000:052A to 0539h is not affected by the settings of this table.
o For keys defined as shift keys, functions such as INT 18h - Function 00h will prevent single character input.
Related 0000:053Ah (Shift key pressed status flag)
INT 18h - Function 02h
Memory 0000:0410-0413h
Type DWORD
Name KB_BUFFER_ADR
Category KEYBOARD BIOS
Target High-Resolution
Content Keyboard buffer address
Initial value = 0000:0502h
Explanation o The top address of the key buffer used by the keyboard BIOS. If you want to secure a key buffer
larger than the initial state, prepare a memory area for the key buffer, change this address and
0000:0522h (key buffer size), and execute INT 18h - Function 06h.
Related 0000:0522h
INT 18h - Function 06h
Memory 0000:0414-0417h
Type DWORD
Name KB_ENTRY_TBL_ADR
Category KEYBOARD BIOS
Target High-Resolution
Contents First address of key data conversion table
Initial state = Table in ROM BIOS
Explanation o First address of conversion table used when generating key data from key number and shift state.
o By replacing the key data conversion table with a user-defined one, you can change to any key assignment.
Related INT 18h - Function 09h
0000:05C6h
Memory 0000:0418-041Bh
Type DWORD
Name KB_INT_ADR
Category KEYBOARD BIOS
Target Hi-Res
Contents Keyboard interrupt table address
Initial state = Table in ROM BIOS
[Setting table structure]
-------+----------------+-------------------------
Offset | Contents | Initial value
-------+----------------+-------------------------
+0 | Number | 02h
+1 | Key number (1) | 60h (INT 06h occurs: STOP key)
+2 | Key number (2) | E1h (INT 05h occurs: COPY key)
-------+----------------+-------------------------
* Number...Number of key codes to be set from the next address onwards.
* Key number...Specify which key generates an INT 05h or INT 06h interrupt with bit 7.
bit 7 = 1:INT 05h, 0:INT 06h
Explanation o Address of the table that defines which keys generate INT 05h, INT 06h when pressed.
o In high-resolution mode, you can redefine which keys generate INT 05h, INT 06h to any key.
o Keys that are specified to generate an interrupt will not be able to input a single character, such as INT 18h - Function 00h.
Related INT 05h
INT 06h
Memory 0000:041C-041Dh
Type WORD
Name PR_TIME
Category PRINTER BIOS
Target Hi-Res
Contents Printer timeout value (unit: 10ms)
Initial value = 0000h.
(If set to 0000h, there will be no timeout)
Explanation o When outputting characters with the printer BIOS, if the printer is BUSY, this specifies the
maximum time to wait while monitoring for BUSY.
o When INT 1Ah - Function 10h is executed, 0190h (4 seconds) is set. Can be set to any value with INT 1Ah - Function 16h.
Related INT 1Ah - Function 10h
INT 1Ah - Function 16h
Memory 0000:041E-0443h
Type 38 BYTES
Name
Classification BRANCH
Undocumented
Target PC-9864 first generation/U+ high resolution
Contents
--------+----------+---------------+------------------------------------------------------------------
Address | Size | Name | Contents
--------+----------+---------------+------------------------------------------------------------------
041Eh | 5BYTES | VD_PRT | Protocol for sending to the server. INT 1Bh Stores parameters for emulation.
041Eh | BYTE | VD_CMD | Request code
| | | 01h = Send (INT 1Bh - Function 05h)
| | | 02h = Receive (INT 1Bh - Function 06h)
041Fh | BYTE | VD_SEC_UNIT | Number of transfer sectors
0420h | BYTE | VD_DRIVE | Virtual drive number (INT 1Bh AL LSB 4bit)
| | | 00-03h
0421h | BYTE | VD_TRACK | Track number (INT 1Bh DH)
0422h | BYTE | VD_SEC | Sector number (INT 1Bh DL)
0423h | BYTE | VD_NUL | Null data
0424h | WORD | VD_REMAIN_SEC | Number of remaining sectors
0426h | WORD | VD_REMAIN_LEN | Number of remaining data bytes (INT 1Bh BX)
0428h | WORD | VD_DATA_OFF | Offset address of transfer data (INT 1Bh BP)
042Ah | BYTE | VDISK_EQUIP | Virtual disk mount status
042Bh | BYTE | BRANCH_INT | External interrupt number of BRANCH4670 I/F
| | | 00h = INT0(INT 0Bh)
| | | 01h = INT41(INT 12h)
| | | 02h = INT5(INT 14h)
| | | 03h = INT6(INT 15h)
042Ch | DWORD | BRANCH_WORK | Pointer to VD_BOOT_WORK (0000:0430h)
0430h | 16BYTES | VD_BOOT_WORK | Work area when booting from a virtual disk
0430h | WORD | | Information about socket 80h
0432h | WORD | | Information about socket 90h
0434h | WORD | | Information about socket A0h
0436h | WORD | | Information about socket B0h
0438h | WORD | | Result record address
043Ah | BYTE | | Used by external interrupt handler
| | | bit 7-4: Unused
| | | bit 3: Processing related to socket B0h
| | | bit 2: Processing related to socket A0h
| | | bit 1: Processing related to socket 90h
| | | bit 0: Processing related to socket 80h
043Bh | BYTE | | Unknown purpose (used by the BIOS ROM installed in the PC-9864U)
| | | Initial value = 04h
| | | Unused by the internal BRANCH BIOS
043Ch | BYTE | | Unknown purpose (used by the BIOS ROM installed in the PC-9864U)
| | | Initial value = FFh
| | | Unused by the internal BRANCH BIOS
043Dh | BYTE | | Unknown purpose (used by the BIOS ROM installed in the PC-9864U)
| | | Initial value = FFh
| | | Unused by the internal BRANCH BIOS
043Eh | BYTE | | Unknown purpose (used by the BIOS ROM installed in the PC-9864U)
| | | Unused by the internal BRANCH BIOS
043Fh | BYTE | | CPU type (used by the BIOS ROM installed in the PC-9864U)
| | | 01h:8086,V30
| | | 02h:80286
| | | 04h:386 or higher
| | | Unused in the main unit's BRANCH BIOS
0440h | DWORD | VD_ADD | Virtual disk BIOS entry address.
| | | When DA/UA=6nh is set when INT 1Bh is executed, processing is transferred to the address specified here.
--------+----------+---------------+------------------------------------------------------------------
Explanation o Virtual disk work area for BRANCH4670-II. Details unknown.
o When the original PC-9864 is installed in a main unit with high-resolution mode, the main unit's BRANCH 4670 BIOS handles it.
The ROM on the original PC-9864 is not used (as it is for normal mode only).
o When the PC-9864U is installed in a high-resolution mode system, both the BRANCH 4670 BIOS in the system
and the ROM on the PC-9864U handle the BRANCH 4670.
Related 0000:0400h bit 0
0000:041E-0443h
0000:0480h bit 5
0000:049A-04ABh
0000:05E5-05E7h
F800:7FE0h
Memory 0000:041E-0443h
Type 38 BYTES
Name
Classification BRANCH
Undocumented
Target PC-9864U + Normal
Contents
--------+-----------+---------------+------------------------------------------
Address | Size | Name | Contents
--------+-----------+---------------+------------------------------------------
041Eh | 13BYTES | | Unused
042Bh | BYTE | BRANCH_INT | External interrupt number of BRANCH4670 I/F
| | | 00h=INT0(INT 0Bh)
| | | 01h=INT41(INT 12h)
| | | 02h=INT5(INT 14h)
| | | 03h=INT6(INT 15h)
042Ch | DWORD | | FAR Address for CALL. Executed before each process in BRANCH BIOS.
| | | If it returns with CF=0, BRANCH BIOS processing will be performed.
| | | If it returns with CF=1, BRANCH BIOS processing will not be performed.
0430h | 10BYTES | | Unused
043Ah | BYTE | | Used by external interrupt handler
043Bh | BYTE | | Initial value set by PC-9864U = 04h
| | | bit 7=Unknown
| | | bit 6=INT D3h - Function 0Dh operation specification
| | | bit 5=INT D3h - Function 03h operation specification
| | | bit 4=INT D3h - Function 01h operation specification
| | | bit 3=INT D3h - Function 07h operation specification
| | | bit 2=Unknown
| | | If bit 1=1 and 042Ch≠0, call 0000:042Ch
| | | bit 0=Unknown
043Ch | BYTE | | Unknown
| | | Initial value = FFh
043Dh | WORD | | Unknown
| | | Initial value = FFFFh
043Fh | BYTE | | CPU type
| | | 01h:8086,V30
| | | 02h:80286
| | | 04h:386 or higher
0440h | DWORD | | Unused
--------+-----------+---------------+------------------------------------------
Explanation o Virtual disk work area for BRANCH4670II. Details unknown.
o Used by the BRANCH BIOS ROM on the PC-9864U. The original PC-9864 does not use this work area.
Related 0000:0480h bit 5
0000:049Ah-04ABh
0000:05E5-05E7h
Memory 0000:0444-0447h
Type DWORD
Name CAL_ROOT_LIST
Classification TIMER BIOS
Target Hi-Res
Content First address of multi-event timer parameter block
Explanation o Address of the first parameter block of the multi-event timer set by INT 1Ch - Function 04h, 05h.
Related INT 1Ch - Function 04h
INT 1Ch - Function 05h
Memory 0000:0448h-0449h
Type WORD
Name CAL_BEEP_TIME
Category CRT BIOS, TIMER BIOS
Target Hi-Res
Content BEEP duration counter (unit: 10ms)
Explanation o INT 18h - Function 24h, INT 1Ch - Remaining time of BEEP sounded by Function 06h.
Related INT 18h - Function 24h
INT 1Ch - Function 06h
Memory 0000:044Ah-044Bh
Type WORD
Name CAL_TONE
Category CRT BIOS, TIMER BIOS
Target Hi-Res
Content BEEP tone (8253A division value)
Explanation o BEEP frequency specified by Function 06h.
Related INT 18h - Function 23h
INT 1Ch - Function 06h
Memory 0000:044Ch-044Fh
Type DWORD
Name CAL_USER_OFF/SEG
Classification TIMER BIOS
Target High-Resolution, PC-98DO+
Contents Single-event timer timeout address
Explanation o Address of the user routine to be called when the single-event timer times out.
u In PC-98DO+, INT 07h contains emulation processing to skip coprocessor instructions, so this work area is used.
Related INT 1Ch - Function 02h
Memory 0000:0450h
Type WORD
Name CRT_FONT
Category CRT BIOS
Undocumented
Target High-resolution
Contents Character code to be output to the character generator
0000:0450h = Value to be output to I/O 00A3h
0000:0451h = Value to be output to I/O 00A1h
Explanation o When INT 18h - Function 1Fh, 20h (reading/registering font pattern (24 dots)) is executed, the character
code to be output to the character generator (value to be output to I/O 00A1h, 00A3h) is stored.
Related INT 18h - Function 1Fh
INT 18h - Function 20h
I/O 00A1h
I/O 00A3h
Memory 0000:0452-0454h
Type 3BYTES
Name RT_P1, RT_P2. RT_P3
Classification CRT BIOS
Undocumented
Target High-resolution
Contents
--------+-------------+----------------------------------------------------
Address | Bit | Contents
--------+-------------+----------------------------------------------------
0452h | | RT_P1
| bit 7 | Cursor display status
| | 1=Yes
| | 0=No
| bit 6,5 | 00b
| bit 4-0 | Number of rasters per CRT line - 1
| | Same as 0000:053Bh
--------+-------------+----------------------------------------------------
0453h | | RT_P2
| bit 7,6 | Lowest 2 bits of cursor blink rate
| bit 5 | Cursor blinking status
| | 1=No blinking
| | 0=Blinking
| bit 4-0 | The top position of the block cursor, with the top of the character's body face at line 0.
--------+-------------+----------------------------------------------------
0454h | | RT_P3
| bit 7-3 | The bottom position of the block cursor, with the top of the character's body face at line 0.
| bit 2-0 | The upper 3 bits of the cursor blink rate. 00000b cannot be specified for all 5 bits of the blink rate.
--------+-------------+----------------------------------------------------
Explanation o Work area for saving parameters of the CSRFORM command issued to the text GDC. Used by
INT 18h - Function 0Ah, 10h, 11h, 12h, 1Ch, 1Eh. In the normal mode of the PC-H98, a value is set in
this area at startup, but it is not used by the BIOS, etc. It is thought that this is the result of
initial settings in normal mode, as in the case of high-resolution mode. MENU Set in the BIOS.
Related INT 18h - Function 0Ah INT 18h - Function 10h INT 18h - Function 11h
INT 18h - Function 12h INT 18h - Function 1Ch INT 18h - Function 1Eh
Memory 0000:0455h
Type 8bit FLAGS
Name
Classification Undocumented
Target PC-9801DA/DS/DX and later models, PC-98HA
Contents
■PC-9801DA/FA
bit 7: 1 = Start after displaying the system setup menu
0 = Normal startup
* If you reset while holding down the [HELP] key, the system setup menu will be displayed
■98NOTE
bit 5: 1 = Start in AUTO mode of the NOTE menu
0 = Normal startup
* If you reset while holding down the [COPY] key, the AUTO mode will start
■PC-9821Ap/As/Ae
bit 5: 1 = The [ESC] key was pressed when reset
0 = The [ESC] key was not pressed when reset
bit 4: 1 = The [COPY] key was pressed when reset
0 = The [COPY] key was not pressed when reset
■PC-98HA
bit 7: Unknown. RESUME, power control related.
bit 6-0: Unused
Related INT 1Fh - Function 99h
INT 1Fh - Function BAh
Explanation Details unknown. It appears to store the state of the keys pressed at the time of reset.
Memory 0000:0456h
Type BYTE
Name
Classification RESUME
Undocumented
Target 98NOTE (excluding PC-9801N/NS), PC-98HA, DB-P1
Contents RESUME power-off prohibition counter
Explanation o In the BIOS, this becomes a value other than 00h during the power-off prohibition period. A mechanism to
allow RESUME to be performed normally.
o During BIOS processing, it is incremented at the beginning of the power-off prohibition period, and
decremented when it becomes possible to turn off the power. This allows processes that require power-off
prohibition to be nested.
Related
Memory 0000:0457h
Type BYTE
Name
Classification IDE
Undocumented
Target Machines with IDE HDD
Contents IDE drive capacity (1)
--------+---------------------------
Bit | Contents
--------+---------------------------
Bit 7 | Sector length of 1st IDE
| 1 = 512 bytes
| 0 = 256 bytes, no drive
Bit 6 | Sector length of 2nd IDE
| 1 = 512 bytes
| 0 = 256 bytes, no drive
Bit 5-3 | Capacity value of 1st IDE HD
Bit 2-0 | Capacity value of 2nd IDE HD
--------+---------------------------
* 00h for machines that do not support IDE, 3Fh for machines that support IDE and do not have IDE HD
---------------+---------------
Capacity value | Drive capacity
---------------+---------------
000b | No drive
001b | 120MB
010b | Number of cylinders is variable
011b | 0000:05B0h indicates capacity
100b | 20MB
101b | 80MB
110b | 40MB
111b | No drive
---------------+---------------
Explanation o Indicates the capacity of the IDE HD.
u The supported range of values indicating drive capacity varies depending on the model.
Related 0000:05B0h
Memory 0000:0458h
Type 8bit FLAGS
Name BIOS_FLAG5
・bit 7
Classification Model identification
Target All models
Contents NESA (H98) identification
1 = NESA architecture machine
0 = Other
Explanation o Indicates NESA architecture machine (PC-H98, SV-H98, FC-H98).
Related
・bit 6
Classification Model identification
Target All models
Contents PC-98GS identification
1 = Multimedia architecture
0 = Other
Explanation o Indicates multimedia architecture machine (PC-98GS).
Related
・bit 5,4
Classification
Target
Content Unused(?)
Explanation
Related
・bit 3
Classification CPU speed
Target PC-H98
Content 486SX flag
1 = 486SX mode
0 = 386 equivalent mode
Explanation o On PC-H98S, PC-H98 model80/90, when CPU speed is set to 486SX (highest speed), it becomes 1.
When set to 386 equivalent (medium/low speed), it becomes 0.
Related
・bit 2
Name Current printer interface mode bit
Classification PRINTER BIOS
Target Normal
Content Printer interface mode
1 = Full Centronics mode
0 = Simple Centronics mode (initial state)
Explanation o Indicates the current printer interface mode. PC-H98 and machines equipped with IEEE STD 1284
support simple Centronics and full Centronics in normal mode. This bit indicates the current mode.
u It also becomes 1 in high-resolution mode on the 98 high-resolution board (PC-9821A-E02).
It becomes 0 in high-resolution mode on other models.
Related 0000:05B3h
INT 1Ah - Function 17h
INT 1Ah - Function 19h
INT 1Ah - Function 1Ah
INT 1Ah - Function 1Bh
・bit 1
Name Full-centro available bit
Classification PRINTER BIOS
Target Normal
Content Printer interface type
1 = Full Centronics mode available
0 = Full Centronics mode not available
Explanation o Indicates whether full Centronics mode is available in normal mode.
o The models with this bit set to 1 are as follows.
- PC-H98 (normal mode)
- Models with IEEE STD 1284
o If the 98 Hi-Res board (PC-9821A-E02) is installed in the PC-9821Ap2, As2, An, Ap3, or As3,
this bit will be 0. This is because in both normal and high-res modes, only the printer interface
on the 98 Hi-Res board is active.
o Hi-res mode is always full Centronics mode, so this bit is 0.
Related 0000:05B3h
INT 1Ah - Function 17h
INT 1Ah - Function 19h
INT 1Ah - Function 1Ah
INT 1Ah - Function 1Bh
・bit 0
Classification Undocumented
Target
Content Unknown. Always 1 on the PC-H98.
Explanation: p.93 of the "Revised Edition Technical Data Book Hardware Edition" states that the i386SL(98) determination
can be done with this bit, but in reality, the determination should be done with 0000:0458h bit 0.
Related
Memory 0000:0459h
Type BYTE
Name CRT_EXT_STS
・bit 7,6
Classification CRT BIOS
Undocumented
Target PC-H98
Contents Extended attribute mode
------+-------------------------------------------
Value | Contents
------+-------------------------------------------
11b | (Reserved)
10b | Extended attribute EGH mode
01b | Extended attribute JEH mode
00b | Previously compatible attribute PC mode (startup setting)
------+-------------------------------------------
Explanation o INT 18h - Mode setting information bits 7,6 of Function 2Ah,2Bh.
Related INT 18h - Function 2Ah
INT 18h - Function 2Bh
・bit 5
Classification TIMER BIOS
Undocumented
Target PC-H98 (Hi-Res)
PC-9821A-E02 (Hi-Res)
Contents Timer BIOS single event timer in use flag
1 = In use
0 = Not in use
Explanation u This flag is not used in the Hi-Res mode of PC-98XA, XL, XL^2, and RL.
Related INT 1Ch - Function 02h
・bit 4
Classification
Target
Contents Unused(?)
Explanation
Related
・bit 3(1/2)
Classification CRT BIOS
Undocumented
Target PC-H98 (Hi-Res)
PC-9821A-E02 (Hi-Res)
Contents Raster scan mode
1 = Non-interlace
0 = Interlace
Explanation o This bit becomes 1 under the following conditions.
- Hi-Res mode when an N5926-02 display is connected to a PC-H98.
- When the [GRPH]+[2]+[RESET] setting is performed in Hi-Res mode on the 98 Hi-Res board (PC-9821A-E02).
Related INT 0Ah (External interrupt...VSYNC)
INT 18h - Function 2Bh [PC-H98]
・bit 3 (2/2)
Classification CRT BIOS
Undocumented
Applicable PC-98GS, PC-9821 (normal), PC-9801BA2/BS2/BX2
Contents Raster scan mode
1 = Non-interlace
0 = Interlace
Explanation o Mode setting information bit 0 for INT 18h - Function 30h, 31h.
The meaning of the value is reversed from that of the BIOS.
o Becomes 0 when the horizontal scan frequency of the PC-98GS is 15.73kHz mode.
o The only models with an initial value of 1 are the PC-98GS and the first generation PC-9821/Ce.
For models other than the above, it is 0. However, on models other than the PC-98GS, the interlace signal is not actually output.
Related INT 18h - Function 30h
INT 18h - Function 31h
・bit 2
Classification CRT BIOS
Undocumented
Target PC-H98
Contents Border color
1 = Follow I/O set value (value set in INT 18h - Function 2Ch)
0 = Follow VRAM attribute (startup setting)
Explanation o Mode setting information bit 2 of INT 18h - Function 2Ah, 2Bh.
Related INT 18h - Function 2Ah
INT 18h - Function 2Bh
INT 18h - Function 2Ch
・bit 1
Classification CRT BIOS
Undocumented
Target PC-H98
Content Unknown (startup setting = 0)
Explanation o INT 18h - Function 2Ah, 2Bh mode setting information bit 1.
Valid in both normal and high-resolution modes.
Related INT 18h - Function 2Ah
INT 18h - Function 2Bh
・bit 0
Classification CRT BIOS
Undocumented
Target PC-H98 (normal)
PC-98GS, PC-9821 (excluding Bf, Bp, Bs, Be, Ts, Ne3, Nd2)
Content CRT resolution 480 line flag
1 = 640x480
0 = 640x400, 640x200 (startup setting)
Explanation o In PC-H98, INT 18h - Function 2Ah, 2Bh mode setting information bit 0.
In normal mode, it can be set to 1 when the horizontal scan frequency is 31.47kHz.
On PC-98GS and PC-9821 (except Bf, Bp, Bs, Be, Ts, Ne3, and Nd2), it is set to
1 when the graphic resolution is set to 640x480 in INT 18h - Function 30h.
Related 0000:054Ch bit 5
INT 18h - Function 2Ah
INT 18h - Function 2Bh
INT 18h - Function 30h
INT 18h - Function 31h
INT 18h - Function 42h
Memory 0000:045Ah
Type BYTE
Name BIOS_FLAG6
Category CPU speed
Undocumented
Target
Content CPU speed
■[Before change]
bit 7-0: CPU, clock
02h = 386SX 10MHz (this model does not actually exist)
04h = 486SX 16MHz
05h = i386SL(98) 20MHz
* Described in the technical data book.
■[After change]
bit 7-4: CPU type
0000b = CPU type
0001b = 486DX2, WriteBackEnhanced IntelDX2
0010b = IntelDX4, IntelDX4ODP
0011b = PentiumODP(P24T)
0100b = Unknown
0101b = 486DX2, WriteBackEnhanced IntelDX2
0110b = OverDriveProcessor for DX4
1000b = Pentium processor 60/66MHz version (P5)
1001b = Pentium processor 90/100MHz version (P54C)
1010b = OverDriveProcessor for 3.3V-Pentium
1011b = Pentium processor 133MHz version
1100b = Unknown CPU
1101b = Pentium Pro ODP (P55CT)
1111b = Unknown CPU
bit 3-0: Clock
0010b = 25MHz external for Pentium processors (P5, P54C, P54CT)
0011b = 30MHz external for Pentium processors (P5, P54C)
0100b = 33MHz external for Pentium, Pentium Pro processors (P5, P54C, P55CT)
0101b = 20MHz external for DX2, DX4, P24T
0110b = 25MHz external for DX2, DX4, P24T
0111b = 33MHz external for DX2, DX4, P24T, ODP for DX4
Explanation o This work area is documented in the revised TDB, H/W section, but the meaning of work
area has actually changed since then. The upper 4 bits are used to determine the value.
o On some models, the value of this work area is not set precisely, so it is not very reliable.
Related 0000:0484h bit 3-0
Memory 0000:045Bh
Type 8bit FLAGS
Name BIOS_FLAG7
・bit 7
Classification TIME STAMPER
Target All models (except PC-H98)
Content Presence or absence of wait function when I/O 005Fh is output
1 = Yes
0 = No
Explanation o Indicates the presence or absence of a function that inserts a wait of about 0.6μs (or more)
in hardware when the OUT 5Fh,AL command is executed.
The models with this bit set to 1 are as follows.
- PC-9801FA, BA, BX, BA2, BS2, BX2, NS/R, NX/C, P, NS/A, NL/R
- PC-9801NA (486SX 20MHz, 386 20MHz equivalent mode)
- PC-9821 (except the first generation)
u In the PC-9801FS, FX, US, the first generation PC-9821, and the PC-9801NA (V30 10MHz equivalent mode),
this bit is set to 0, but the BIOS uses OUT 5Fh,AL to wait.
u Even when the OUT 5Fh,AL command is executed on a model with this bit set to 0, a wait of 0.6μs (or more)
is actually inserted by the hardware. However, in the first generation PC-9801, E, F, and M, care must be
taken because this I/O address overlaps with the I/O decoded image of the 320KB FD I/F.
o The PC-H98 has a wait function, but this bit is 0. If 0000:0458h bit 7 (NESA identification bit) = 1,
it can be determined that the wait function is present.
Related 0000:0458h bit 7
I/O 005Fh
・bit 6
Classification
Target
Content Unused(?)
Explanation
Related
・bit 5
Classification POWER
Undocumented
Target PC-9801NS/T･NS/R･NX/C･P･NL/R
Content Power save mode
1 = Set
0 = Do not set
Explanation o Indicates the state of the power save mode set in the 98NOTE menu.
o Power save mode cannot be set on the PC-9801NL/R･NX/C, but is always 1.
o Power save mode can be set on the PC-9801NL, but this bit does not change.
u For the PC-9801NS/R･P, the power save mode will not be enabled unless you reset it once after setting it.
Related I/O 851Eh
・bit 4
Classification PCMCIA
Undocumented
Target PC-9801NL
Content PCMCIA memory card BIOS BUSY
1 = PCMCIA memory card BIOS running
0 = PCMCIA memory card BIOS not running
Explanation o Becomes 1 during PCMCIA memory card BIOS processing. PCMCIA device drivers do not manipulate this bit.
Related INT 1Fh - Function B4h
INT 1Fh - Function B5h
INT 1Fh - Function B6h
INT 1Fh - Function B7h
INT 1Fh - Function B8h
・bit 3
Classification
Undocumented
Target All models
Content Unknown
Explanation o Models with this bit set to 1 are PC-9801NL/NS/R/NX/C/P.
Related
・bit 2
Classification TIME STAMPER
Target All models (except PC-H98)
Content Presence or absence of time stamper function
1 = Yes
0 = No
Explanation o Indicates the presence or absence of time stamper function. The models with this bit set to 1 are as follows.
- PC-9801FS, FX, US, BA, BX, BA2, BS2, BX2
- PC-9821
- 98NOTE (except PC-9801N, NS, NV, NS/E, NC)
o PC-H98 has a time stamper function, but this bit is 0. If 0000:0458h bit 7 (NESA identification bit) = 1,
it can be determined that the time stamper function is present.
Related 0000:0458h bit 7
I/O 005Ch
I/O 005Eh
・bit 1
Classification
Undocumented
Target All models
Content Presence or absence of card slot I/O function (?)
1 = Card slot I/O function
0 = No card slot I/O function
Explanation o Details unknown. The models with this bit set to 1 are as follows.
- 98NOTE (excluding PC-9801N, NS, NV, NS/E, and NC)
Related
・bit 0
Classification CPU identification
Undocumented
Target All models
Content i386SL(98) identification
1 = 386SL(98)
0 = Other
Explanation o Only PC-9801NS/T models are equipped with i386SL(98). It is always 0 on other models.
u "Revised Edition Technical Data Book Hardware Edition" p.93 states that i386SL(98) determination can be done
at 0000:0458h bit 0, but in reality, this bit must be used to make the determination.
Related
Memory 0000:045Ch
Type 8bit FLAGS
Name
・bit 7
Classification CPU
Target Other than PC-H98
Content 486SX flag
1 = Equivalent to 486SX
0 = Other
Explanation o The models and modes in which this bit is 1 are as follows.
- HIGH mode of PC-9821As, As2, Ce, Cs2, Ce2, Ne, Ts, Xe
- HIGH mode of PC-9801FA, NA, NS/A
- MIDDLE mode of PC-9821Ap, As, As2
Related
・bit 6
Classification Model discrimination
Target Normal
Content Extended graph architecture identification
1 = Extended graph architecture machine
0 = Other
Explanation o Indicates whether the PC-9821 extended graph architecture is supported. The models in which this bit is 1 are as follows.
- PC-9821 (except Bf, Bp, Bs, Be, Ts, Ne3, Nd2)
u The 98 high-resolution board (PC-9821A-E02) also shows 1 in high-resolution mode, but extended graphics cannot be used.
Related INT 18h - Function 30h
INT 18h - Function 31h
・bit 5
Classification CRT
Undocumented
Applicable PC-9801NA and later 98NOTE
Content Color LCD identification
1 = Color LCD
0 = Monochrome LCD
Explanation o Indicates whether or not it is a color LCD model. The models with this bit set to 1 are as follows.
- PC-9801NA/C, NX/C, PC-9821Ne
o The PC-9801NC has a color LCD, but this bit is 0.
Related I/O 00F0h bit 7 [PC-9801NA/NA/C]
I/O 8810h bit 5 [PC-9801NS/R/NX/C/NS/A/NL/R, PC-9821Ne/Np]
・bit 4
Classification
Target
Content Unused (?)
Explanation
Related
・bit 3
Classification DISK
Undocumented
Target PC-9801NL
Content ROM drive write prohibition flag
1 = Write permitted
0 = Write prohibited (initial state)
Explanation o Flag for permitting ROM drive writes with INT 1Fh - Function 94h. Set/reset with INT 1Fh - Function 9Dh.
Related INT 1Fh - Function 94h
INT 1Fh - Function 9Dh
・bit 2
Classification Undocumented
Target 98NOTE (excluding PC-9801N, NS, NV, NS/E, NC, NL/R)
Contents PC-9801N-08 (expansion I/O box) connected or not
1 = Connected
0 = Not connected
Explanation o Indicates whether or not the expansion I/O box for 98NOTE is connected.
Related I/O 8810h bit 0
・bit 1
Classification SMM
Undocumented
Target 98NOTE (excluding PC-9801N, NS, NV, NS/E, NC, NL, NS/L, NA)
Content Power save mode prohibition flag
1 = Prohibits transition to power save mode
0 = Allows transition to power save mode
Explanation o Indicates the setting status of INT 1Fh - Function 9Eh Subfunction 02h, 03h.
u Note that the meaning of INT 1Fh - Function 9Eh Subfunction 02h, 03h is reversed for PC-9801NS/T only.
The meaning of this bit is the same for all target models.
Related INT 1Fh - Function 9Eh Subfunction 02h,03h
・bit 0
Classification CPU
Undocumented
Target 98NOTE with coprocessor,
PC-9821A-E02 (98 high-res board) high-res (excluding PC-9821An)
Content Presence or absence of numerical calculation coprocessor function
1 = Coprocessor function available
0 = No coprocessor function
Explanation o When the coprocessor function is available with i387SX, i486DX, i487SX, i486DX(J), ODP486SX, Pentium, etc., it becomes 1.
u For models without description in the target column, it will be 0 even if the coprocessor function is available.
Connection
Memory 0000:045Dh
Type 8bit FLAGS
Name
・bit 7
Classification Advanced Power Management BIOS
Undocumented
Target PC-9801P
Content Unknown
Explanation o Details unknown. Used in INT 1Fh - Function 9Axxh of PC-9801P.
Related
・bit 6
Classification BOOT
Undocumented
Target PC-9801BA･BX･BA2･BS2･BX2･BA3･BX3･BX4･NS/R･NX/C･P･NS/A･NL/R･NL/A
PC-9821 (except the first generation) Normal
Content Use ROM BASIC
1 = Do not use
0 = Use
Explanation o Shows the setting status of "Use/Do not use ROM BASIC" in the system setup menu.
o 98NOTE is 1 if it is set to anything other than "Start ROM BASIC" in the 98NOTE menu.
Always 1 for PC-9801P.
Related
・bit 5
Classification Undocumented
Target PC-9801NS/R･NX/C･P･NS/A･NL/R, PC-9821Ne
Content Unknown
Explanation o Details unknown. Used for RAM drive, boot process, and power management.
Related
・bit 4
Classification IDE BIOS
Undocumented
Target PC-9821Bp･Bs･Be･Bf･Cs2･Ce2, PC-9801BA2･BS2･BX2･BA3･BX3･BX4
Content High-speed IDE flag for second IDE HDD
1 = High-speed IDE
0 = Non-high-speed IDE
Explanation o Indicates whether the second IDE HDD is a high-speed IDE HDD.
Related 0000:045Dh bit 3
0000:045Eh bit 6
0000:045Eh bit 5
・bit 3
Classification IDE BIOS
Undocumented
Applicable PC-9821Af･Ap2･As2･An･Bp･Bs･Be･Bf･Cs2･Ce2, PC-9801BA2･BS2･BX2
Contents High-speed IDE flag of the first IDE HDD
1 = High-speed IDE
0 = Non-high-speed IDE
Explanation o Indicates whether the first IDE HDD is a high-speed IDE HDD.
Related 0000:045Dh bit 4
0000:045Eh bit 6
0000:045Eh bit 5
・bit 2,1
Classification
Target
Content Unused(?)
Explanation
Related
・bit 0
Classification SCSI BIOS
Undocumented
Target PC-9801-100
Content I/O address used by PC-9801-100
1 = I/O 387Eh~
0 = I/O 187Eh~
Explanation o Indicates the I/O address used by the SCSI-2 interface board PC-9801-100.
Related
Memory 0000:045Eh
Type 8bit FLAGS
・bit 7
Name
Classification Undocumented
Target PC-9821Bp, Bs, Be, Bf, Ts
Content Unknown
Explanation o Details unknown. May be set to 1 by ITF.
Related I/O 006Ah - 80h,81h
・bit 6
Classification IDE BIOS
Undocumented
Target PC-9821Xa10, Xa9, Xa7, Xa12
Content High-speed IDE flag for third IDE HDD
1 = High-speed IDE
0 = Non-high-speed IDE
Explanation o Indicates whether the third IDE HDD is a high-speed IDE HDD.
Related 0000:045Dh bit 3
0000:045Dh bit 4
0000:045Eh bit 5
・bit 5
Classification IDE BIOS
Undocumented
Target PC-9821Xa10, Xa9, Xa7, Xa12
Contents High-speed IDE flag of 4th IDE HDD
1 = High-speed IDE
0 = Non-high-speed IDE
Explanation o Indicates whether the 4th IDE HDD is a high-speed IDE HDD.
Related 0000:045Dh bit 3
0000:045Dh bit 4
0000:045Eh bit 6
・bit 4-0
Classification
Target
Contents Unused
Explanation
Related
Memory 0000:045Fh
Type BYTE
Name
Classification
Target
Contents Unused(?)
Explanation
Related
Memory 0000:0460-047Fh
Type 32 BYTES
Name
Classification SCSI BIOS
Undocumented
Target PC-9801-55 original/55L/55U/92/100, PC-H98-B03/B12, PC-9821X-B02,
Equivalent built-in SCSI interface
Contents Parameter table for SCSI devices
[Address and SCSI ID correspondence]
-----------+---------------------------------
Address | Contents
-----------+---------------------------------
0460-0463h | Parameter table for SCSI ID #0
0464-0467h | Parameter table for SCSI ID #1
0468-046Bh | Parameter table for SCSI ID #2
046C-046Fh | Parameter table for SCSI ID #3
0470-0473h | Parameter table for SCSI ID #4
0474-0477h | Parameter table for SCSI ID #5
0478-047Bh | Parameter table for SCSI ID #6
047C-047Fh | Unused *1
-----------+---------------------------------
*1 The device with SCSI ID #7 is not recognized. 0 is always stored.
[Table structure (1)]
(Hard disk cylinder count bit width <12 bits>)
-------+-----------+---------------------------------
Offset | Bit | Contents
-------+-----------+---------------------------------
+0h | bit 7-0 | Number of sectors/track
+1h | bit 7-0 | Number of heads
+2h | bit 7-0 | Number of cylinders bits 7-0
+3h | bit 7 | Sector type
| | 1 = Hard sector
| | 0 = Soft sector
| bit 6 | Specify number of cylinders bit width
| | 1 = See table structure (2)
| | 0 = 12 bits
| bit 5,4 | Sector length
| | 10b = 1024 bytes
| | 01b = 512 bytes
| | 00b = 256 bytes
| bit 3-0 | Number of cylinders bits 11-8
-------+-----------+---------------------------------
[Table structure (2)]
(Hard disk cylinder number bit width <16 bits>)
-------+-----------+---------------------------------
Offset | Bit | Content
-------+-----------+---------------------------------
+0h | bit 7-0 | Number of sectors/track
+1h | bit 7-4 | Number of cylinders bits 15-12
| bit 3-0 | Number of heads
+2h | bit 7-0 | Number of cylinders bits 7-0
+3h | bit 7 | Sector type
| | 1 = Hard sector
| | 0 = Soft sector
| bit 6 | Number of cylinders bit width specification
| | 1 = 16 bits
| | 0 = See table structure (1)
| bit 5,4 | Sector length
| | 10b = 1024 bytes
| | 01b = 512 bytes
| | 00b = 256 bytes
| bit 3-0 | Number of cylinders bits 11-8
-------+-----------+---------------------------------
* The original PC-9801-55 does not support a 16-bit cylinder number bit width.
Other SCSI I/Fs (including built-in types) do support it.
[Table structure (3)]
(Other than hard disk)
-------+-----------+------------------------------------------
Offset | Bit | Content
-------+-----------+------------------------------------------
+0h | bit 7-6 | Peripheral Qualifier
| bit 5-0 | Peripheral Device Type
| | 00h=Direct access device (hard disk)
| | 01h=Sequential access device (magnetic tape)
| | 02h=Printer device
| | 03h=Processor device
| | 04h=Write once device (Optical disk)
| | 05h=CD-ROM device
| | 06h=Scanner device
| | 07h=Optical memory device (3.5"MO)
| | 08h=Media change device
| | 09h=Communication device
| | 1Fh=Undefined device type
+1h | bit 7 | RMB(Removable)
| | 1=replaceable medium
| | 0=non-replaceable medium
| bit 6～0 | Device Type Modifier
+2h | bit 7～0 | Not used (00h)
+3h | bit 7～0 | Not used (00h)
-------+-----------+---------------------------------------
Explanation o Device parameters for each SCSI ID are stored.
u When INT 1Bh - Function 84h (SCSI) is executed, the BIOS returns the drive parameters based on
the data written to this address, rather than querying the SCSI device for parameters.
u When the system starts up and INT 1Bh - Function 03h (SCSI) is executed, the SCSI BIOS checks the
connection status of SCSI devices. Of the information obtained, the presence or absence of a hard
disk connection for each SCSI ID is set to 0000:0482h, and the drive parameters are set in this area.
The contents of the addresses corresponding to IDs to which no SCSI devices are connected are all 0.
When devices other than hard disks are connected, the values shown in
"Table structure (3) (other than hard disks)" are set.
u With the PC-H98-B12, PC-9801-92･100, PC-9821X-B02 (and the above-mentioned built-in SCSI interfaces),
HDDs made by manufacturers other than NEC can be connected. When a HDD other than that manufactured
by NEC is connected, the total capacity of the drive is obtained using the SCSI Read Capacity command,
and the number of cylinders is calculated assuming the number of heads = 08h and the number of
sectors = 20h. For this reason, the number of heads and the number of sectors are always set to fixed
values.
u In MS-DOS 3.3D, 5.0 and later, when a 3.5"MO/5"MO drive is connected, MS-DOS rewrites the parameters.
The parameters can be obtained in the same way as for hard disks using INT 1Bh - Function 84h (SCSI).
However, since MS-DOS 3.3D does not support 3.5"MO, the parameters are rewritten only when a 5"MO drive
is connected.
If INT 1Bh - Function 03h (SCSI) is executed after MS-DOS starts, the data set by MS-DOS will be
corrupted, and random values will be read when INT 1Bh - Function 84h (SCSI) is executed, but this does
not seem to affect operation. The parameters set by MS-DOS are as shown in the table below. However,
the first generation PC-9801-55 only supports a cylinder number bit width of <12 bits>, so all items
other than the sector length are set to 0.
Table [Parameters set by MS-DOS]
--------------------+---------+-----------------
Item | 5"MO | 3.5"MO(128MB) *1
--------------------+---------+-----------------
Sector length | 1024 | 512
Number of cylinders | 4656 | 9952
Number of heads | 1 | 1
Number of sectors | 64 | 25
--------------------+---------+-----------------
*1: MS-DOS 5.0A only supports 128MB 3.5"MO drives, so this parameter is set even if
a 230MB 3.5"MO drive is connected.
Related 0000:0482h
0000:05A5h
0000:05AFh
INT 1Bh - Function 84h (SCSI)
INT DCh - Function 09h
Memory 0000:0480h
Type 8bit FLAGS
Name SYS_TYPE
BIOS_FLAG1
・bit 7
Classification DISK BIOS
Undocumented
Target Normal
Contents SASI/IDE BIOS new sense command support
1 = Supported
0 = Not supported
Explanation o Indicates whether INT 1Bh - Function 84h (SASI/ESDI/IDE) is supported.
o The BIOS on the PC-9801-27 (5-inch fixed disk interface board) and the BIOS
supporting the PC-9801-07 (5-inch fixed disk interface board) do not support
INT 1Bh - Function 84h (SASI/ESDI/IDE), so this bit is 0. The built-in SASI
BIOS of the PC-9801F3/M3/VM4 is the same as this, as it is a compatible BIOS.
However, in MS-DOS environments after MS-DOS 3.1 (PS98-011), MS-DOS traps and
emulates INT 1Bh - Function 84h (SASI/ESDI/IDE). In this case, this bit is set
to 1.
o The built-in SASI BIOS, ESDI BIOS, IDE BIOS, and PC-H98 built-in HD BIOS of
the PC-9801VX4 and later support INT 1Bh - Function 84h (SASI/ESDI/IDE), and
this bit is 1.
o The SASI BIOS in high-resolution mode (in the F800h segment of the main
unit) also supports INT 1Bh - Function 84h (SASI/ESDI/IDE), but this bit is 0.
However, even in high-resolution mode, when an IDE HD is built in, the IDE
BIOS sets this bit to 1.
o ESDI BIOS (PC-H98/70-E02) DA/UA is SASI upward compatible, but this flag is
0 and INT 1Bh - Function 84h is supported.
o In PC-H98 built-in SASI HDD (PC-H98/70-E01/E03 compatibility mode, this flag
is 1. However, in extended mode, INT 1Bh - Function 84h (SASI/ESDI/IDE) is
supported, but this bit is 0.
o SCSI BIOS always supports INT 1Bh - Function 84h (SCSI).
Related INT 1Bh - Function 84h (SASI/ESDI/IDE)
・bit 6
Classification GRAPHIC
Undocumented
Target Normal
Content EGC compatible high-speed graphic processing
1 = Supported
0 = Not supported
Explanation o When drawing graphics with the graphic BIOS or graphic LIO, this bit indicates whether the routine in the ROM uses EGC.
o The following models and modes have this bit set to 0:
- PC-9801 original, E, F, M, U, VF, VM2, VM21, VX2, UV2, UV21
- PC-9801VX21 (V30 8MHz/10MHz, 80286 8MHz)
The following models and modes have this bit set to 1:
- PC-9801VX21 (80286 10MHz)
- Normal modes other than the above
Only the PC-9801VX21 has this bit change depending on the mode of the same model.
o It also indicates 1 in the high-resolution mode of the PC-H98 and the high-resolution mode of the 98 high-resolution board (PC-9821A-E02).
Related I/O 0439h bit 1
・bit 5
Classification BRANCH 4670
Undocumented
Target All models
Content Presence or absence of PC-9864U
1 = PC-9864U is implemented
0 = PC-9864U is not implemented
Explanation o If PC-9864U is implemented, it becomes 1 (both normal and high resolution).
o The first generation PC-9864 does not set this bit.
Related 0000:0400h bit 0
・bit 4
Classification DISK BIOS
Target Dual-use BIOS - 1MB I/F mode
(Excluding PC-9801VM2･VM21･UV2･UV21･VX2･VX21･UX, PC-98XA･XL)
Content Dual-use 1MB I/F FD motor control
1 = Automatic stop mode
0 = Always ON
Explanation o When INT 1Bh - Function 83h (FD) is executed, this bit becomes 1.
There is no BIOS function that sets this bit to 0.
o Some models are set to motor stop mode from the time of startup, and some models allow you to select the startup mode in the system setup menu.
Related 0000:0485h
INT 1Bh - Function 83h(FD)
I/O 00BEh bit 2
・bit 3
Classification DISK BIOS
Undocumented
Target Dual-use BIOS (excluding PC-9801VM2/VM21/UV2/UV21/VX2/VX21, PC-98XA/XL)
Contents Type of drive last accessed
1 = Dual-use FDD
0 = 1MB dedicated external FDD
Explanation u No change if the RAM drive is accessed.
Related
・bit 2
Classification POWER
Target PC-9801LV/N/NS
Contents LOW BATTERY
1 = LOW BATTERY alarm generated
0 = Not LOW BATTERY
Explanation o On PC-98901LV/N, NMI occurs when LOW BATTERY occurs. NMI handler sets this bit to 1.
On the PC-9801NS, the INT 0Eh handler checks for LOW BATTERY, and if it is, sets this bit to 1.
Related I/O 8810h bit 1
・bit 1,0
Classification CPU discrimination
Target All models
Contents Extended CPU type
■PC-H98
11b = 386 8MHz equivalent mode other than
00b = 386 8MHz equivalent mode
■PC-9801NS/NA
11b = V30 10MHz equivalent mode other than
00b = V30 10MHz equivalent mode
■PC-98XA
00b = i80286 8MHz
■Other than the above (actual operating CPU)
11b = i386, i486, Pentium
01b = i80286
00b = i8086, V30, V30HL, V50, V33
Explanation o For models other than PC-H98 and PC-9801NS/NA, indicates the actual operating CPU.
Related
Memory 0000:0481h
Type 8bit FLAGS
Name KEYB_TYPE, BIOS_FLAG3
・bit 7
Classification SHUT DOWN
Undocumented
Target PC-H98 (excluding model 70)
Contents Work when operating the shutdown port
Explanation o Details unknown
Related I/O 00F0h
・bit 6
Classification KEYBOARD
Target All models
Contents Keyboard identification (1)
-----+-----+-------------------------------------
bit 6|bit 3|Keyboard type
-----+-----+-------------------------------------
1 | 1 | New keyboard (with NUM key, DIP2-7 OFF)
0 | 1 | New keyboard (with NUM key, DIP2-7 ON)
1 | 0 | New keyboard (without NUM key)
0 | 0 | Old keyboard
-----+-----+-------------------------------------
Explanation o Indicates the type of keyboard connected.
The BIOS of a machine that supports the new keyboard checks the keyboard type at reset and sets this bit.
- When no keyboard is connected to the PC-9801P (when an external keyboard is connected,
the value is 11b or 01b according to DIP SW 2-7).
Related DIP SW 2-7
0000:0481h bit 3
・bit 5
Classification EMS
Undocumented
Target Normal
Contents NEC B0000h bank EMS page frame memory
1 = Yes
0 = No
Explanation o Indicates the presence or absence of page frame memory for use with the software emulation method EMS (EMM.SYS).
o Indicates 1 in normal mode on models with i80286 or later CPUs (excluding PC-9801VX2･VX21･UX, PC-98XA･XL･XL^2, PC-9821Np･Ns･Ne2･Nd･Xa･Xt).
u EMS emulation is not possible in V30 mode or V30 equivalent mode, but this memory itself can be accessed. This bit is also 1.
Related I/O 043Fh - 20h,22h
・bit 4
Classification EMS
Undocumented
Target Normal
Contents Bank status when using NEC B0000h bank EMS
1 = Page frame
0 = G-VRAM
Explanation o Indicates the bank status when using NEC B0000h bank EMS. EMM uses it as a work area.
Related I/O 043Fh - 20h,22h
・bit 3
Classification KEYBOARD
Target All models
Contents Keyboard identification (2)
Explanation o See 0000:0481h bit 6.
Related 0000:0481h bit 6
・bit 2
Classification MEMORY
Undocumented
Target PC-98RL, PC-H98, PC-9821A-E02 (Hi-Res)
Content Hi-Res memory window test result
1 = Usable
0 = Unusable
Explanation o Indicates the operation check result of the memory window of I/O 0091h, 0093h.
o In the Hi-Res mode of the PC-98RL, PC-H98, 98 Hi-Res board (PC-9821A-E02), it is usually 1.
In the Hi-Res mode of other models, this bit indicates 0, but the memory window of I/O 0091h, 0093h can be used.
u In the PC-H98 ITF, when an error is detected and it is unusable, "EMS ERROR" is displayed.
EMM.SYS (software emulation type EMM) does not check this bit.
Related I/O 0091h
I/O 0093h
・bit 1
Classification HD BIOS
Undocumented
Target SASI, IDE (normal mode only)
Content SASI/IDE HD #1 mode
1 = Thick drive, sector length 512 bytes
0 = Thick drive, sector length 256 bytes, or thin drive
Explanation o Details unknown. See INT 1Bh - Function 0Eh (SASI/ESDI/IDE).
u On PC-9801CV/LV/UV11/N, this bit is always 1 even if a second SASI is not connected. The reason is unknown.
Related 0000:0590h bit 1
0000:05ECh
INT 1Bh - Function 0Eh (SASI/ESDI/IDE)
・bit 0
Classification HD BIOS
Undocumented
Target SASI, IDE (normal mode only)
Content SASI/IDE HD #0 mode
1 = thick drive, sector length 512 bytes
0 = thick drive, sector length 256 bytes, or thin drive
Explanation o Details unknown. See INT 1Bh - Function 0Eh (SASI/ESDI/IDE).
Related 0000:0590h bit 0
0000:05E8h
INT 1Bh - Function 0Eh (SASI/ESDI/IDE)
Memory 0000:0482h
Type 8bit FLAGS
Name DISK_EQUIPS
Classification SCSI HD BIOS
Target PC-9801-55 first generation, 55L, 55U, 92, 100, PC-H98-B03, B12,
PC-9821X-B02
PC-9821A-E10
Equivalent to the above built-in SCSI interface
Content SCSI HD connection status
------+--------------------------
Bit | Device
------+--------------------------
bit 7 | Unused
bit 6 | SCSI ID #6(DA/UA=A6h,26h)
bit 5 | SCSI ID #5(DA/UA=A5h,25h)
bit 4 | SCSI ID #4(DA/UA=A4h,24h)
bit 3 | SCSI ID #3(DA/UA=A3h,23h)
bit 2 | SCSI ID #2(DA/UA=A2h,22h)
bit 1 | SCSI ID #1(DA/UA=A1h,21h)
bit 0 | SCSI ID #0(DA/UA=A0h,20h)
------+--------------------------
1 = HDD connected
0 = HDD not connected
Explanation o Indicates the connection status of the SCSI HD. The SCSI BIOS checks the connection of the hard disk
when resetting or executing the initialization function, and stores the result in this area.
o Only valid for SCSI hard disks. IDs connected to MO, CD-ROM, etc. will not be 1.
Related 0000:0460h
0000:055Ch
0000:05A5h
0000:05AFh
INT 1Bh - Function 03h(SASI/SCSI/ESDI/IDE)
Memory 0000:0483h
Type 8bit FLAGS
Name
Classification SCSI BIOS
Undocumented
Target PC-9801-55 first generation, 55L, 55U, 92, 100, PC-H98-B03, B12,
PC-9821X-B02
PC-9821A-E10
Equivalent built-in SCSI interface
Contents SCSI status
--------+------------------------------------------------
Bit |Contents
--------+------------------------------------------------
bit 7-4 | Value obtained by converting bits 7-4 of the WD33C93(A) end status
| 0100b: When WD33C93(A) status is 0000b
| 0000b: When WD33C93(A) status is 0001b
| 0001b: When WD33C93(A) status is 0010b
| 0010b: When WD33C93(A) status is 0100b
| 0011b: When WD33C93(A) status is 1000b
bit 3-0 | Value of bits 3-0 of WD33C93(A) end status
--------+------------------------------------------------
00h = Reselect command completed successfully
01h = Select command completed successfully
03h = Receive, Send, Reselect and Trasfer, Wait for Receive
Command completed successfully (no ATN)
04h = Receive, Send, Reselect and Trasfer, Wait for Receive
Command completed successfully (no ATN)
06h = Select and Transfer command completed successfully
08h = Transfer command completed successfully (data out phase)
09h = Transfer command completed successfully (data in phase)
0Ah = Transfer command completed successfully (command phase)
0Bh = Transfer command completed successfully (status phase)
0Ch = Transfer command completed successfully (unspecified information out phase)
0Dh = Transfer command completed successfully (unspecified information in phase)
0Eh = Transfer command completed successfully (message out phase)
0Fh = Transfer command completed successfully (message in phase)
10h = Transfer command (message in phase) paused with ACK asserted
11h = Save data pointer message received during Select and Transfer command
12h = Select, Reselect command aborted
13h = Receive, Send command halted or aborted (no ATN)
14h = Receive or Send command was halted or aborted (ATN present)
18h = Transfer command was aborted (data out phase)
19h = Transfer command was aborted (data in phase)
1Ah = Transfer command was aborted (command phase)
1Bh = Transfer command was aborted (status phase)
1Ch = Transfer command was aborted (unspecified information out phase)
1Dh = Transfer command was aborted (unspecified information in phase)
1Eh = Transfer command was aborted (message out phase)
1Fh = Transfer command was aborted (message in phase)
20h = Invalid command was aborted
21h = Command terminated and disconnected
22h = Timeout during execution of Select or Reselect command
23h = Parity error occurred and command was terminated (no ATN)
24h = Parity error occurred and command was terminated (ATN)
26h = Incorrect target device reselected
27h = Received message, status, or command was inappropriate
28h = Unexpected info phase request (data out phase)
29h = Unexpected info phase request (data in phase)
2Ah = Unexpected info phase request (command phase)
2Bh = Unexpected info phase request (status phase)
2Ch = Unexpected information phase request (unspecified information outphase)
2Dh = Unexpected information phase request (unspecified information inphase)
2Eh = Unexpected information phase request (message outphase)
2Fh = Unexpected information phase request (message inphase)
30h = Reselected
32h = Selected (no ATN)
33h = Selected (with ATN)
34h = ATN signal already asserted
35h = Disconnect occurred
38h = REQ is asserted following a connection (data out phase)
39h = REQ is asserted following a connection (data in phase)
3Ah = REQ is asserted following a connection (command phase)
3Bh = REQ is asserted following a connection (status phase)
3Ch = REQ is asserted following a connection (unspecified info out phase)
3Dh = REQ is asserted following a connection (unspecified info in phase)
3Eh = REQ was asserted following a connection (message out phase)
3Fh = REQ was asserted following a connection (message in phase)
40h = Reset due to command or MR input
Explanation o A value generated from the end status of the SCSI controller (WD33C93) is stored.
End status returned to the AH register after executing INT 1Bh - Function nnh (common to SCSI).
Related INT 1Bh - Function nnh (common to SCSI)
Memory 0000:0484h
Type BYTE
Name CPU_TYPE, BIOS_FLAG4
・bit 7,6
Classification HD BIOS
Applicable PC-9801RA21･RS･DA･DS･DX･FA･FS･FX, PC-98GS, PC-98RL,
PC-9821Ap･As･Ae･Af･Ap2･As2･An
Contents DMA channel of built-in hard disk interface
11b = Channel 3
10b = Channel 2
01b = Channel 1
00b = Channel 0, no built-in hard disk
Explanation o Indicates the DMA channel used by the built-in hard disk interface.
In models that can accommodate any of the following: PC-9801RA-37,
PC-9801DA-37, PC-98RL-37, PC-9801FA-02, PC-9821A-E10, the ITF in the main unit sets these bits.
When a SASI-type built-in HDD is installed in the PC-9801RA21/RS/DA/DS/DX, PC-98GS, or PC-98RL,
or when a SCSI interface is simply inserted into the SCSI interface slot of the PC-9801FA/FS/FX,
or PC-9821Ap/As/Ae/Af/Ap2/As2/An, these bits are set.
The PC-9801RA2/RX2/RX21 and PC-H98 do not use these bits.
o PC-9801RA-37, PC-9801DA-37, PC-98RL-37 have a 100MB SCSI built-in HDD.
PC-9801FA-02, PC-9821A-E10 have a SCSI I/F compatible with the SCSI interface
slots of PC-9801FA/FS/FX, PC-9821Ap/As/Ae/Af/Ap2/As2/An.
Related I/O 0CC4h
I/O 00F0h bit 6,5
I/O 00F6h
I/O 7FDBh bit 4■PC-98RL
DIP SW 3-3
・bit 5
Classification HD BIOS
Undocumented
Applicable PC-9801RA21･RS･DA･DS･DX･FA･FS･FX,PC-98GS,PC-98RL,
PC-9821Ap･As･Ae･Af･Ap2･As2･An
Contents Presence or absence of built-in SCSI interface
1 = Built-in SCSI
0 = No built-in SCSI
Explanation o Indicates the presence or absence of a built-in SCSI interface.
u In models that can accommodate any of the following: PC-9801RA-37,
PC-9801DA-37, PC-98RL-37, PC-9801FA-02, PC-9821A-E10, the ITF inside the main
unit sets this bit.
u This bit will be set to 1 even if a SCSI interface is simply inserted into the SCSI interface slot
of the PC-9801FA/FS/FX, PC-9821Ap/As/Ae/Af/Ap2/As2/An.
o The PC-9801RA2/RX2/RX21 and PC-H98 do not use this bit because they cannot implement the above SCSI type built-in HDD (I/F).
Related I/O 00F0h bit 6
・bit 4
Classification HD BIOS
Undocumented
Target PC-9801RA21･RS･DA･DS･DX･FA･FS･FX,PC-98GS,PC-98RL,
PC-9821Ap･As･Ae･Af･Ap2･As2･An
Contents Presence or absence of built-in SASI interface
1 = Built-in SASI
0 = No built-in SASI
Explanation o Indicates the presence or absence of a built-in SASI interface. It will not become 1 even if an IDE HDD is built in.
u In models that can be equipped with any of the following: PC-9801RA-37,
PC-9801DA-37, PC-98RL-37, PC-9801FA-02, PC-9821A-E10, the ITF in the main unit sets this bit.
o This bit becomes 1 when a SASI type built-in HDD is installed in the PC-9801RA21/RS/DA/DS/DX, PC-98GS,
or PC-98RL, or when hardware DIP SW 5 is turned ON (using the PC-9801FA-03 expansion 3.5-inch fixed disk drive
connection unit) in the PC-9801FA/FS/FX. For the PC-9821Ap/As/Ae/Af/Ap2/As2/An, this bit becomes 0 even if you set
"Use Disk Connection Unit" in the system setup menu.
o The PC-9801RA2/RX2/RX21 and PC-H98 do not use this bit.
Related I/O 00F0h bit 5
・bit 3 to 0
Classification CPU speed
Target All models
Content CPU type/clock discrimination
■PC-H98
------+------------------------+------------------------------------------
Value |CPU clock | Representative model name (mode)
------+------------------------+------------------------------------------
1110b | 486DX2 66MHz | PC-H98 model105(H)
1110b | 486SX 16MHz | PC-H98 model80(H)
1010b | 486 20MHz | PC-H98S(H)
1000b | 486 25MHz (equivalent) | PC-H98 model90(H)･100(H)･105(M)
0110b | 386 33MHz (equivalent) | PC-H98 model70(H)･90(M)･100(M)
0100b | 386 25MHz | PC-H98 model60(H)
0010b | 386 20MHz equivalent | PC-H98 model60(M)･70(M), PC-H98S(M)
0000b | 386 16MHz equivalent | PC-H98 model80(M)
0000b | 386 8MHz equivalent | PC-H98(L)
------+------------------------+------------------------------------------
■When running i386, i486, Pentium (other than PC-H98)
------+--------------------------+------------------------------------------
Value | CPU clock | Representative model name (mode)
------+--------------------------+------------------------------------------
1111b | 386SL 20MHz | PC-9801NS/T
1110b | Pentium 90MHz | PC-9821An(H)･Xn(H)
1110b | Pentium 60MHz | PC-9821Af(H)
1110b | DX4 100MHz | PC-9821Xp(H)
1110b | DX4 75MHz | PC-9821Np(H)
1110b | 486DX2 66MHz | PC-9821Ap(H)･Bp(H)･Xs(H)
1110b | ODP486SX 33MHz | PC-9821As(H)ODP
1110b | 486SX 33MHz | PC-9821Xe
1110b | 486SX 16MHz | PC-9801FA
1110b | 486SX(J) 16MHz | PC-9801NS/R
1110b | 486 16MHz equivalent | PC-9821Ap(M)･As(M)･Bp(M)
1110b | V30 8MHz equivalent | PC-9801NS/T
1100b | 486DX 33MHz | PC-9821As(H)
1100b | 486 33MHz equivalent | PC-9821Af(M)･An(M)
1010b | 486SX 20MHz | PC-9801NA
1010b | 486SX(J) 20MHz | PC-9801P･NX/C
1000b | 486SX 25MHz | PC-9821Ae(H)･Ce(H)
0011b | 386SX 20MHz | PC-9801T・NC・NS/L,PC-98GS, | |PC-9821 first generation(H)・Ce(H)
0010b | 386 20MHz equivalent | PC-9801NA(M)
0010b | 386 20MHz equivalent | PC-9801Ae(M)
0010b | 386DX 20MHz | PC-9801DA･RA21,PC-98RL
0010b | V30 10MHz equivalent | PC-9801NC(L)
0001b | 386SX 16MHz | PC-9801ES･RS･LS･US･DS･NS/E
0001b | 386SX 12MHz | PC-9801NS(H)
0001b | 386 16MHz equivalent | PC-9801FA(M)
0001b | 386SX 20MHz power saving | PC-9801NS/L
0000b | 386DX 16MHz | PC-9801RA2･RA21･DA,PC-98XL^2･RL
0000b | V30 10MHz equivalent |
0000b | V30 8MHz equivalent |
------+--------------------------+------------------------------------------
* When the value is 1110b, there are models where more detailed clock
information is provided at 0000:045Ah.
* Even when the value is V30 10MHz equivalent, the system clock is not necessarily 10MHz
(such as PC-9801NS/E).
* Even when the value is V30 8MHz equivalent, the system clock is not necessarily 8MHz
(such as the first generation PC-9821).
■When running i80286 (except PC-98XA)
(0000:0480h bit 1,0=01b)
------+----------------------+------------------------------------------
Value | CPU clock | Representative model name (mode)
------+----------------------+------------------------------------------
0010b | 80286 12MHz | PC-9801EX･RX2･RX21･LX･DX
0000b | 80286 10MHz | PC-9801VX21･UX･EX･RX2･RX21･LX･DX, PC-98XL
0000b | 80286 8MHz | PC-9801VX2･VX21･RX2･RX21･DX, PC-98XL
0000b | V30 10MHz equivalent | PC-9801DX
------+----------------------+------------------------------------------
■PC-98XA
(0000:0480h bit 1,0=00b)
------+--------------------+------------------------------------------
Value | CPU clock | Model name (mode)
------+--------------------+------------------------------------------
0000b | 80286 8MHz | PC-98XA
------+--------------------+------------------------------------------
■8086, V30, V30HL, V33A, V50, V50HL operation
(0000:0480h bit 1,0=00b)
------+----------------------+------------------------------------------
Value | CPU clock | Representative model name (mode)
------+----------------------+------------------------------------------
0010b | V33A 16MHz | PC-98DO+(H)
0010b | V30HL 16MHz | PC-9801NV･NL･UR(H)
0000b | V33A 8MHz | PC-98DO+(L)
0000b | V30HL 8MHz | PC-9801NV･NL･UR(L)
0000b | V50HL 10MHz | DB-P1
0000b | V50 10MHz | PC-98HA
0000b | V50 8MHz | PC-98LT
0000b | V30 10MHz equivalent | PC-9801NA･NS
0000b | V30 10MHz |
0000b | V30 8MHz |
0000b | 8086 8MHz |
0000b | 8086 5MHz |
------+----------------------+------------------------------------------
* The PC-9801NA and NS are i486SX and i386SX machines (not equipped with V30), but when set to
V30-equivalent mode, they are classified here because 0000:0480h bit 1,0=00b is set.
Explanation o Varies depending on CPU type and clock. However, the correspondence between CPU speed and value is not necessarily well organized.
o Bit 0 indicates 1 for i386SX and i386SL (98).
o The method for determining the operating CPU is as follows.
-----------------------------------------------------+-----------------------
Operating CPU | Determination method
-----------------------------------------------------+-----------------------
PC-H98 | 0000:0458h bit 7=1
When running i386, i486, Pentium (other than PC-H98) | 0000:0458h bit 7=0 and
| 0000:0480h bit 1,0=11b
When running i80286 (other than PC-98XA) | 0000:0480h bit 1,0=01b
PC-98XA | 0000:0501h bit 5,3=01b
When running 8086, V30, V30HL, V33A, V50, V50HL | 0000:0458h bit 7=0 and
| 0000:0480h bit 1,0=00b
-----------------------------------------------------+-----------------------
Related CPU speed
Memory 0000:0485h
Type BYTE
Name
Classification DISK BIOS
Undocumented
Target Dual-use BIOS - 1MB I/F mode (excluding PC-9801VM2/VM21/UV2/UV21/VX2/VX21, PC-98XA/XL)
Content Motor stop counter (unit: 100ms)
Explanation o Counter used when motor stop mode is set with INT 1Bh - Function 83h(FD).
u When disk I/O ends, the value of 0000:05CBh (initial value of motor stop
time) is copied. It is decremented by 1 by an interrupt that occurs every
100ms with FDC, and when it reaches 0, the motor stops.
Related 0000:05A4h
0000:05CBh
0000:05D7h
INT 1Bh - Function 83h(FD)
Memory 0000:0486-0487h
Type WORD
Name
Classification CPU
Undocumented
Target i386 (excluding PC-98XL^2), i486, Pentium equipped machines
Contents DX register value when CPU is reset
------+--------------------------------+-------------------------------------
Value | CPU | Main installed models, comments, etc.
------+--------------------------------+-------------------------------------
0303h | i386DX(B0,B1 Step) | PC-98XL^2(Virtual 86, Windows inoperable)
0305h | i386DX(D0 Step) | PC-9801RA2
0308h | i386DX(D1,D2 Step) | PC-9801RA21･DA,PC-H98 model70
2304h | i386SX(A0 Step) |
2305h | i386SX(B Step) | PC-9801ES･RS･LS
2308h | i386SX(C Step) | PC-9801T･NS･NS/E･NC･NS/L･RS･DS･US,
| | PC-98GS,PC-9821 first generation
33xxh | i376 | Embedded CPU
430xh | i386SL(A-step) | Microprocessor Superset for ISA
431xh | i386SL(B-step) | Microprocessor Superset for ISA
5300h | i386SL(98) | PC-9801NS/T
0340h | RapidCAD |
A301h | IBM 386SLC(step 1) | Reference
0400h | i486DX(A0 Step) |
0401h | i486DX(B3～B6 Step) |
0402h | i486DX(C0 Step) |
0403h | i486DX(C1 Step) |
0404h | i486DX(D0 Step) | PC-H98 model100, PC-9821As
0410h | i486DX(cA2/cA3 Step) |
0411h | i486DX(cB2/cB3 Step) |
0420h | i486SX(A0 Step) | PC-9801FA, PC-H98 model90, PC-H98S
0420h | i487SX(A0 Step) |
0421h | i487SX(B0 Step) |
0422h | i486SX | PC-9801NA, PC-9821Ae･Ce (QFP)
0423h | i486SX SL Enhanced,5.0V | PC-9801BX3 (PGA)
0424h | i486SX SL Enhanced,3.3V | PC-9821Ne,PC-9801NS/A (SQFP)
0427h | i486SX(cA0 Step) | PC-486GR (QFP)
0428h | i486SX(cB0 Step) | PC-486SR (QFP)
042Ah | i486SX SL Enhanced,5V | PC-9821As2 (QFP)
0432h | i486DX2(A Step) |
0432h | ODP486SX(A2 Step) |
0433h | i486DX2(B Step) | PC-H98 model105, PC-9821Ap, PC-9801BA
0433h | ODP486SX(B1 Step) |
0435h | i486DX2 SL Enhanced,5V | PC-9801BA2,PC-9821Bp･Ap2 (PGA)
044xh | i486SL | Microprocessor Superset for ISA
045xh | i486SX2 |
0460h | i486SX(J) | PC-9801NS/R･P･NX/C･NL/R
0470h | i486DX2 WB Enhanced | PC-9821As3,PC-9801BA3
0480h | iDX4 75MHz,100MHz | PC-9821Xp･Np
043xh | AMD DX2 | Reference
047xh | AMD DX2 WB | Reference
048xh | AMD DX4 | Reference
049xh | AMD DX4 WB | Reference
041xh | UMC U5D (DX equivalent) | Reference
042xh | UMC U5S (SX equivalent) | Reference
A412h | IBM 486SLC | Reference
A422h | IBM 486SLC2 | Reference
0513h | Pentium 60MHz(PGA Sera) | PC-9821Af･Bf
0515h | Pentium 60MHz(PGA Gold) | PC-9821Cf
0521h | Pentium 90MHz(SPGA) | PC-9821An･Xt･Xa･Xn
0524h | Pentium 90MHz(TAB) | PC-9821Nf (FPU bug-free version)
153xh | ODP486DX2(P24T) |
------+--------------------------------+-------------------------------------
------+--------------------------------+-------------------------------------
Value | Military i486 DX CPU |
------+--------------------------------+-------------------------------------
0401h | i486DX(B3,B4,B5,B6 Step) | From Military and Special Products II
0402h | i486DX(C0 Step) |
0404h | i486DX(D0 Step) |
0411h | i486DX(CB0 Step) |
------+--------------------------------+-------------------------------------
* The table includes CPUs not installed in the PC-9800 series.
Description o Holds the value of the DX register (CPU ID) when the CPU is reset.
u When the system starts, immediately after processing moves from the ITF to
the BIOS initialization routine, the BIOS internally shuts down (resets) the
CPU. The value of the DX register at that time is written to this address. Of
the models equipped with an i386 or later CPU, only the PC-98XL^2 does not
store the CPU ID at this address. The table lists the CPU versions that the
PC-98XL^2 was equipped with at the time of shipment, but this value is not
actually stored (0000h is shown).
u When operating at V30 or in a mode equivalent to V30, this address value is
0000h. However, only the PC-9801NS, NS/E, NS/L, and NS/T store the CPU ID in
the same way as in i386 mode, even in V30-equivalent mode.
Related I/O 00F0h
Memory 0000:0488h
Type 8bit FLAGS
Name RDISK_EQUIP
Category DISK BIOS,RAM DRIVE
Target Machines with RAM drive (including PC-98HA, DB-P1)
Contents RAM drive connection status
------+---------------
Bit | Device
------+---------------
bit 7 | 640KB FD UNIT#3
bit 6 | 640KB FD UNIT#2
bit 5 | 640KB FD UNIT#1
bit 4 | 640KB FD UNIT#0
bit 3 | 1MB FD UNIT#3
bit 2 | 1MB FD UNIT#2
bit 1 | 1MB FD UNIT#1
bit 0 | 1MB FD UNIT#0
------+---------------
1 = RAM drive
0 = Non-RAM drive or no drive
Explanation o Indicates which FDD unit number the RAM drive is emulating.
o The unit number of a FDD accessible by the BIOS can be found by checking 0000:055Ch
(connection status of FDD, SASI/ESDI HDD). However, just checking this area does not
tell you whether a drive is a FDD or a RAM drive. Since RAM drives do not allow media
replacement, there are times when you want to distinguish a RAM drive from an
application. In such cases, checking this bit makes it possible to distinguish between
a RAM drive and a FDD.
o At the same time, the bit for the corresponding device number in 0000:055Ch will also
be set to 1 for a RAM drive.
Related 0000:0400h bit 7
0000:055Ch
Memory 0000:0489-048Dh
Type 5 BYTES
Name
Classification DISK BIOS, RAM DRIVE
Undocumented
Target Machines with RAM drive (excluding PC-98HA, DB-P1)
Contents RAM drive BIOS work (jump code)
Explanation o Code for FAR jump from RAM DRIVE BIOS to DISK BIOS entry in ROM BIOS.
Related
Memory 0000:048Eh
Type BYTE
Name
Classification DISK BIOS,RAM DRIVE
Undocumented
Target Machines with RAM drive (including PC-98HA, DB-P1)
Contents RAM drive BIOS work
---------+-----------------------------------------------
Bit |
---------+-----------------------------------------------
Bit 7 | RAM drive BIOS processing flag (excluding PC-9801NS/T)
| 1 = Processing
| 0 = Not processing
Bits 6-4 | Value output to I/O 0E8Eh (machines with SMM)
| When the value output to I/O 0E8Eh is 80-FFh,
| This value is retained.
bit 3 | FDD drive BIOS processing flag (except PC-9801N/NS, PC-98HA, DB-P1)
| 1 = Processing
| 0 = Not processing
bit 2 | RAM drive number (except PC-9801N/NS, PC-98HA, DB-P1)
| 1 = RAM DIRVE is unit #0 (FDD is unit #1)
| 0 = RAM DIRVE is unit #1 (FDD is unit #0)
bit 1,0 | Dual-use BIOS I/F mode
| 10b = 1MB I/F mode
| 01b = 640KB I/F mode
| * PC-98HA, DB-P1 is always 01b.
---------+-----------------------------------------------
Explanation o Stores various statuses of the RAM drive.
Related I/O 0E8Eh
Memory 0000:048Fh
Type BYTE
Name
Classification
Target
Content Unused
Explanation
Related
Memory 0000:0490h-0491h
Type WORD
Name
Classification BEEP
Undocumented
Target Hi-Res
Contents INT 18h - Function 17h beep pitch (unit: 8253A division value)
--------------+------
Timer clock | Initial value
--------------+------
2MHz | 03E6h
2.5MHz | 04CDh
--------------+------
Explanation o Beep pitch used by INT 18h - Function 17h. The setting result of INT 18h - Function 23h (buzzer frequency setting) is stored.
Related INT 18h - Function 17h
INT 18h - Function 23h
Memory 0000:0492h
Type 8bit FLAGS
Name DISK_RESET
Classification FD DISK BIOS
Target Dual-use BIOS
Content Dual-use FD recalibrate request flag
------+---------------
Bit | Device
------+---------------
bit 7 | 640KB FD UNIT#3
bit 6 | 640KB FD UNIT#2
bit 5 | 640KB FD UNIT#1
bit 4 | 640KB FD UNIT#0
bit 3 | 1MB FD UNIT#3
bit 2 | 1MB FD UNIT#2
bit 1 | 1MB FD UNIT#1
bit 0 | 1MB FD UNIT#0
------+---------------
1 = Recalibrate request
0 = No recalibrate request
Explanation o It is set to 1 when the access mode (1MB/640KB) is changed, etc.
The next time it is accessed, a recalibration is performed for the drive whose
bit is 1. When recalibration is complete, the bit is reset to 0.
Related
Memory 0000:0493h
Type 8bit FLAGS
Name F2HD_MODE
Category DISK BIOS
Target Dual-use BIOS - 1MB I/F mode
Contents 640KB FDD access mode
[INT 1Bh - Function 8Eh(FD) setting]
bit 7: 640KB FDD UNIT#3
bit 6: 640KB FDD UNIT#2
bit 5: 640KB FDD UNIT#1
bit 4: 640KB FDD UNIT#0
1 = 80 cylinders (2DD,1DD)
0 = 40 cylinders (2D,1D)
[INT 1Bh - Function 0Eh(FD) setting]
bit 3: 640KB FDD UNIT#3
bit 2: 640KB FDD UNIT#2
bit 1: 640KB FDD UNIT#1
bit 0: 640KB FDD UNIT#0
1 = Double-sided
0 = Single-sided
* Initial value = FFh (2DD/Double-sided)
Explanation o Stores the setting values of INT 1Bh - Function 0Eh, 8Eh in dual-use BIOS - 1MB I/F mode.
Related 0000:05CAh
INT 1Bh - Function 04h(FD)
INT 1Bh - Function 84h(FD)
INT 1Bh - Function 0Eh(FD)
INT 1Bh - Function 8Eh(FD)
Memory 0000:0494h
Type 8bit FLAGS
Name DISK_EQUIP2
Classification DISK BIOS
Target Dual-use BIOS (normal)
Contents Dual-use BIOS, external 1MB drive connection status in 640KB I/F mode
bit 7-4: Drive connection status
1 = connected
0 = not connected
--------+----------------------
Bit | Device
--------+----------------------
bit 7 | Unit #3 (DA/UA=F3h)
bit 6 | Unit #2 (DA/UA=F2h)
bit 5 | Unit #1 (DA/UA=F1h)
bit 4 | Unit #0 (DA/UA=F0h)
bit 3-0 | Unused
--------+----------------------
Explanation o Indicates the 1MB drive connection status in dual-use BIOS, 640KB I/F mode.
u This flag is set only when all of the following conditions are met.
- An external 1MB FD is connected to the 1MB FD I/F connector on the main unit.
- The dual-use FD I/F is set to the automatic detection 640KB I/F mode.
(DIP SW 3-1=OFF, 3-2 ON)
- The dual-use FD I/F is in 640KB I/F mode.
(When booting from a 640KB system disk or a device other than a FD) Only when
this condition is met, will the connection status of the external 1MB FDD be
shown at this address (it will also be available from MS-DOS).
When the dual-use FD I/F is in 640KB I/F mode, the external 1MB FD connected
to the 1MB FD I/F connector on the main unit will only be recognized by the
BIOS under the above conditions.
o In this case, the connection status of the external 1MB FDD is not reflected
in the flag at 0000:055Ch, and the connection can only be confirmed at this
address.
Related 0000:055Ch
Memory 0000:0495h
Type BYTE
Name GRAPH_CHG
Classification GRAPHICS
Target GRCG,EGC equipped devices
Content GRCG/EGC mode register setting
Explanation o GRCG/EGC mode register setting.
Programs that write to GC/EGC must also write to this address at the same
time. This is because programs that access GRCG/EGC within interrupt routines,
such as mouse drivers, refer to the contents of this address to restore the
GRCG/EGC registers.
o When this value is 0, GRCG/EGC is unused.
Related 0000:0496h
I/O 007Ch[Normal]
I/O 00A4h[High-Resolution]
Memory 0000:0496-0499h
Type 4 BYTES
Name GRAPH_TAL
Classification GRAPHICS
Target GRCG,EGC equipped devices
Contents GRCG/EGC tile register setting
--------+----------------
Address |Contents
--------+----------------
0496h | Tile register #0
0497h | Tile register #1
0498h | Tile register #2
0499h | Tile register #3
--------+----------------
Explanation o GRCG/EGC tile register setting.
Used in the same way as 0000:0495h (GRCG/EGC mode register setting).
Related 0000:0495h
I/O 007Eh[Normal]
I/O 00A6h[Hi-Res]
Memory 0000:049A-04ABh
Type 18 BYTES
Name
Classification BRANCH BIOS
Undocumented
Target PC-9864 first generation, U + normal
Contents FAR jump code to original INT B1h/INT 1Bh/INT 1Ah entry
-----------+----------------------------------------------
Address |Contents
-----------+----------------------------------------------
049A-049Fh | FAR jump code to original INT B1h entry
04A0-04A5h | FAR jump code to original INT 1Bh entry
04A6-04ABh | FAR jump code to original INT 1Ah entry
-----------+----------------------------------------------
Explanation o When BRANCH 4670 BIOS is running, FAR jump code to original INT
B1h/INT 1Bh/INT 1Ah entry is stored.
Related 0000:0400h bit 0
0000:041E-0443h
0000:0480h bit 5
0000:05E5-05E7h
F800:7FE0h
Memory 0000:049Bh (DB-P1)
Type 8bit FLAGS
Name
Classification Undocumented
Target DB-P1
Content INT 1Fh - Function B0h,B1h related
bit 3: INT 1Fh - Function B0h,B1h in progress, for saving/restoring I/O FEC6h bit 3
bit 2: INT 1Fh - Function B0h,B1h in progress, for saving/restoring I/O FEC6h bit 2
1 = Display screen plane 1
0 = Display screen plane 0
Explanation o Details unknown.
Related INT 1Fh - Function B0h
I/O FEC6h
Memory 0000:049C-04A1h (DB-P1)
Type 6 BYTES
Name
Classification KEYBOARD BIOS
Undocumented
Target DB-P1
Contents Keyboard handler work area
-------------+-------------------------------------------------
Address | Contents
-------------+-------------------------------------------------
049Ch (BYTE) | Unknown. Initial value = 08h.
049Dh (BYTE) | Keyboard I/F 8251A (I/O 0041h) emulation
049Eh (WORD) | Key pressed status flag (1=ON, 0=OFF)
| bit 13: Work area
| bit 8: [Cancel]
| bit 7: [Table of contents]
| bit 6: [Function]
| bit 5: [Next page]
| bit 4: [Previous page]
| bit 3: [↑]
| bit 2: [←]
| bit 1: [→]
| bit 0: [↓]
04A0h (WORD) | Unknown. Initial value = 0000h
-------------+-------------------------------------------------
Initial value = 08h, FFh, 00h, 00h, 00h, 00h
Explanation o Work area used by the keyboard handler.
o The DB-P1 does not have an 8251A (I/O 0041h) for the keyboard interface, but
for compatibility with the PC-98HA, 0000:049Dh is treated as I/O 0041h for
internal processing. Used by the INT 09h handler.
o INT 18h - Function 04h Subfunction FFh can obtain the status of all keys on
the DB-P1 at once. This function actually just returns the value of 0000:049Eh.
Related INT 18h - Function 04h Subfunction FFh
Memory 0000:04A2-04A3h (DB-P1)
Type 2 BYTES
Name
Classification DISK BIOS
Undocumented
Target DB-P1
Contents DISK BIOS work area
-------------+-----------------------------------------------------
Address | Contents
-------------+-----------------------------------------------------
04A2h (BYTE) | Dual-use FD I/F switching port (I/O 00BEh) for emulation
| Initial value = 0Eh
04A3h (BYTE) | Unknown. Initial value = 0Ch.
-------------+-----------------------------------------------------
Explanation o Work area used by DISK BIOS.
o DB-P1 does not have a dual-use FD I/F switching port (I/O 00BEh), but for
compatibility with PC-98HA, internal processing is performed by treating
0000:04A2h as I/O 00BEh.
Related
Memory 0000:04A4h (DB-P1)
Type 8bit FLAGS
Name
Classification Undocumented
Target DB-P1
Content INT 1Fh - Function 92h (DB-P1) related
bit 7: INT 1Fh - Function 92h Set/clear with Subfunction 02h,03h
bit 0: INT 1Fh - Function 92h Set/clear
Explanation o Details unknown
Related INT 1Fh - Function 92h (DB-P1)
Memory 0000:04A5-04A6h (DB-P1)
Type 2 BYTES
Name
Classification Undocumented
Target DB-P1
Content Used in INT 0Ah handler
-------------+-----------------------------------------------------
Address | Content
-------------+-----------------------------------------------------
04A5h (BYTE) | Unknown. Initial value = 00h.
04A6h (BYTE) | Unknown. Initial value = 00h. Related to INT 70h.
-------------+-----------------------------------------------------
Explanation o Details unknown.
Related INT 0Ah (External interrupt...LT/HA)
Memory 0000:04A7h (DB-P1)
Type 8bit FLAGS
Name
Classification Undocumented
Target DB-P1
Content INT 1Fh - Function 92h (DB-P1) related
bit 3: Check with INT 1Fh - Function 92h
bit 2: Check with INT 1Fh - Function 92h
Explanation o Details unknown.
Related INT 1Fh - Function 92h (DB-P1)
Memory 0000:04AC-04AFh
Type DWORD
Name XROM_PTR
Classification DISK BIOS
Target Normal, High Resolution, PC-98LT/HA, DB-P1
Contents Work area for storing jump destination address of extended DISK BIOS
Explanation o Used to store the jump destination address when FAR jumping from
the INT 1Bh handler of the main BIOS to the extended ROM BIOS.
Related 0000:04B0h
Memory 0000:04B0-04BFh
Type 16 BYTES
Name DISK_XROM
Classification DISK BIOS
Target Normal, High Resolution, PC-98LT/HA, DB-P1
Contents Extended DISK BIOS table
--------+----------------------------------------------
Address | Contents
--------+----------------------------------------------
04B0h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=0xh
04B1h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=1xh
04B2h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=2xh
04B3h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=3xh
04B4h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=4xh
04B5h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=5xh
04B6h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=6xh
04B7h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=7xh
04B8h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=8xh
04B9h | Extended DISK BIOS segment (upper 8 bits) with DA/UA=9xh
04BAh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Axh
04BBh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Bxh
04BCh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Cxh
04BDh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Dxh
04BEh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Exh
04BFh | Extended DISK BIOS segment (upper 8 bits) with DA/UA=Fxh
--------+----------------------------------------------
Explanation o Table showing the ROM address of the extended DISK BIOS.
When an extended DISK BIOS is installed, the upper 8 bits of the BIOS segment
are set to the address corresponding to the DA/UA supported by the BIOS.
For example, when a SCSI I/F is implemented, the SCSI BIOS supports DA/UA=2xh,
Axh, Cxh, so the upper 8 bits (CCh) of the SCSI BIOS segment (usually CC00h)
are set to 04B2h, 04BAh, 04BCh.
The DA/UA when the extended DISK BIOS is not installed is 00h.
u The INT 1Bh handler in the main unit checks this table at the beginning of
processing. Based on the value of AL (DA/UA specification), it checks whether
an extended disk BIOS is registered.
If it is registered, it performs a FAR jump to offset 0018h of the extended
disk BIOS. If it is not registered, the internal disk BIOS will perform the
processing. If a DA/UA that is not supported by the internal disk BIOS is
specified, it will end with an error.
u The internal BIOS of the original PC-9801 does not have the function to
recognize an extended disk BIOS (extended ROM). However, when the ROM included
with the PC-9801-08 (2DD FD I/F exclusive to the original PC-9801) is
installed in a socket inside the main unit, it becomes possible to recognize
the extended disk BIOS. At this time, this extended disk BIOS table is used.
u This table is set by the initialization routine in the extended ROM
(extended disk BIOS).
After a reset, the internal BIOS (except for the original PC-9801) checks
whether there is an extended ROM with a jump table during the initialization
process. If the BIOS determines that an expansion ROM with a jump table
exists, it calls the three entries (offsets 000Ch, 000Fh, 0012h) of the
initialization routine in the jump table of the expansion ROM in sequence. If
the expansion ROM extends the DISK BIOS (i.e., it is an extended DISK BIOS),
the expansion ROM sets this extended DISK BIOS table in the initialization routine.
Related 0000:04ACh
0000:04C0h
Memory 0000:04C0-04F3h
Type 52 BYTES
Name XROM_ID
Category Normal, Hi-Res
Target Hi-Res (except PC-98XA)
Contents Expansion ROM ID table
■ Hi-Res (except PC-98XA)
-----------+-----------------
Address | Contents
-----------+-----------------
04C0h | E6000h Expansion ROM ID
04C1h | E7000h Expansion ROM ID
04C2h | E8000h Expansion ROM ID
04C3h | E9000h Expansion ROM ID
04C4h | EA000h Expansion ROM ID
04C5h | EB000h Expansion ROM ID
04C6h | EC000h Expansion ROM ID
04C7h | ED000h Expansion ROM ID
04C8h | EE000h Expansion ROM ID
04C9h | EF000h Expansion ROM ID
04CA-04CFh | Unused
-----------+-----------------
■Normal
-----------+-----------------
Address | Contents
-----------+-----------------
04D0h | D0000h Expansion ROM ID
04D1h | D1000h Expansion ROM ID
04D2h | D2000h Expansion ROM ID
04D3h | D3000h Expansion ROM ID
04D4h | D4000h Expansion ROM ID
04D5h | D5000h Expansion ROM ID
04D6h | D6000h Expansion ROM ID
04D7h | D7000h Expansion ROM ID
04D8h | D8000h Expansion ROM ID
04D9h | D9000h Expansion ROM ID
04DAh | DA000h Expansion ROM ID
04DBh | DB000h Expansion ROM ID
04DCh | DC000h Expansion ROM ID
04DDh | DD000h Expansion ROM ID
04DEh | DE000h Expansion ROM ID
04DFh | DF000h Expansion ROM ID
-----------+-----------------
* PC-9801E/F/M does not recognize expansion ROMs after D8000h, so 04D8-04DFh are not used.
■PC-98XA
-----------+-----------------
Address | Content
-----------+-----------------
04E0-04E5h | Unused
04E6h | E6000h Expansion ROM ID
04E7h | E7000h Expansion ROM ID
04E8h | E8000h Expansion ROM ID
04E9h | E9000h Expansion ROM ID
04EAh | EA000h Expansion ROM ID
04EBh | EB000h Expansion ROM ID
04ECh | EC000h Expansion ROM ID
04EDh | ED000h Expansion ROM ID
04EEh | EE000h Expansion ROM ID
04EFh | EF000h Expansion ROM ID
04F0h | F0000h Expansion ROM ID
04F1h | F1000h Expansion ROM ID
04F2h | F2000h Expansion ROM ID
04F3h | F3000h Expansion ROM ID
-----------+-----------------
Meaning of Extended ROM ID
--------+------------------------------------------------
Bit | Content
--------+------------------------------------------------
Bit 7 | Extension ROM presence/absence
| 1=Yes
| 0=No
Bit 6 | Jump table presence/absence
| 1=Yes
| 0=No (area after 4K bytes of extended ROM exceeding 4K bytes)
Bit 5-0 | Extended ROM identification code
| Value of 00-3Fh assigned to extended ROM
| (Not necessarily unique value for each ROM)
--------+------------------------------------------------
Extended ROM ID and product name
------------------------+-----------------------------------------------------
Extended ROM ID | Product name
------------------------+-----------------------------------------------------
C0h,80h,80h,80h | D8000h bank of PC-9801N
C2h,82h | PC-9801-55 first generation/L/U, PC-9801-92/100, PC-H98-B03/B12
| (Including built-in types compatible with the above products)
C6h, 86h, 86h, 86h | PC-9864-02, PC-9864L
D0h, 90h, 90h, 90h | D8000h bank of PC-9801NV
D9h | Built-in SASI BIOS of PC-9801-27, PC-9801VX4
E9h, A9h | Built-in SASI BIOS of PC-H98/70-B02 (built-in ESDI) BIOS
E9h | Built-in SASI BIOS of PC-9801VX4, PC-98XL (normal) and later
EAh, AAh, AAh, AAh | D8000h bank of PC-9801NS, UR, US, built-in IDE BIOS of PC-9821
FAh,BAh,BAh,BAh | PC-9801NS/E･NC･NS/T･NL･NS/L･NA･NS/R･P･NX/C･NS/A･NL/R,
| D8000h bank of PC-9821Ne
---------------+-----------------------------------------------------
* If multiple values are written in the Extended ROM ID column, it
indicates that the ROM stores the values in the Extended ROM ID
table in the order of the table. In other words, the ROM occupies an area of
<number of values> x 4K bytes.
* The Extended ROM IDs listed here are only those that the author has been
able to confirm.
Explanation o A table that indicates whether or not there is an expansion ROM with a jump table.
When an expansion ROM with a jump table is placed in the expansion ROM area,
the corresponding address in the expansion ROM ID table is set to a value other than 00h.
For example, when an IDE HD is implemented on a PC-9821, the IDE BIOS occupies
D8000 to DBFFFh, so EAh, AAh, AAh are set to 04D8 to 04DBh.
o Not all expansion ROMs have jump tables. Expansion ROMs that do not have
jump tables include sound BIOS ROMs (installed in PC-9801-26 and 86, etc.),
RS-232C BIOS ROMs (installed in PC-9861), and GP-IB BIOS ROMs (installed in PC-9801-29, etc.).
Expansion ROMs for extending the DISK BIOS always have a jump table. The BRANCH 4670 BIOS
ROM (installed in the PC-9864-02, PC-9864L/U) also has a jump table.
o In normal mode, the presence of an expansion ROM is checked every 4K (1000h)
bytes in the range D0000 to DFFFFh. However, the PC-9801E/F/M only check the
range D0000 to D7FFFh.
o In high-resolution mode, the presence of an expansion ROM is checked every
4K bytes in the range E6000 to EFFFFh. Only the PC-98XA can also use F0000 to
F3FFFh as an expansion ROM area.
u This table is set by an initialization routine in the expansion ROM.
After a reset, the BIOS inside the main unit (except the first-generation
PC-9801) checks for the presence of an expansion ROM with a jump table during
the initialization process. If it determines that an expansion ROM with a jump
table exists, the BIOS in the main unit sequentially FAR CALLs the three
entries (offset 000Ch, 000Fh, 0012h) of the initialization routine in the jump
table of the expansion ROM. The expansion ROM ID is set in the initialization
routine at offset 000Ch.
u The BIOS in the main unit of the original PC-9801 does not use this work
area because it does not have the function to recognize expansion ROMs. When
the ROM included with the PC-9801-08 (2DD I/F exclusive to the original
PC-9801) is installed in the socket in the main unit, it becomes possible to
recognize the expansion ROM, but this work area is not used. This is because
it only FAR CALLs the entry (offset 0000h) of the initialization routine
exclusive to the original PC-9801 in the jump table of the expansion ROM.
Related 0000:04B0h
Memory 0000:04F0h-04F7h
Type 8 BYTES
Name
Classification RAM DRIVE BIOS
Undocumented
Target PC-9801NS/E･NC･NS/T･NL･NS/L･NA･NS/R･P･NX/C
Content RAM DRIVE BIOS work area
Explanation o Used for the following two purposes.
- When the RAM DRIVE BIOS calculates the checksum in the RAM bank, it
transfers the code and executes it at this address. This is thought to be
faster than executing it on ROM.
- Used when a program in the D8000h bank switches the D8000h bank. Write the
bank switching code (OUT command, etc.) to this area, execute this area to
switch banks, and return execution to the D8000h bank (where the bank was
switched).
o PC-9801N･NS･NV･NL/R･NS/A, PC-9821Ne do not use this address.
Related 0000:04F8h
Memory 0000:04F1-04F3h
Name
Classification Hi-Res Timer
Target Models with Calendar Clock Interrupt
Content
Bit 24-0: Elapsed time (unit: 1/32 seconds)
* Represented by a value from 000000-2A2FFFh.
Explanation o Counts the time elapsed since today's date in 1/32 seconds. This
counter is initialized at startup, and is incremented by INT 17h thereafter.
o The time since today's date was set at startup, and the counter overflows at
0:00:00'00 AM and is returned to 0. At this time, INT 1Fh - Function 8Fh is
executed, and midnight is announced to the application. For this reason, this
function, INT 1Fh - Function 8Fh, is named the Cinderella Function (just kidding).
HRTIMER.SYS, which comes with the PC-9821Xa10, Xa9, Xa7, Xt13, Xe10, Xa12,
Xa7e, Cx2, Cb2, Na7, and Nx, replaces the MS-DOS CLOCK device and uses this
counter to provide a function to obtain the time to the 1/100th of a digit.
Related INT 17h
INT 1Ch - Function 80h,81h
INT 1Fh - Function 8Fh
I/O 000Ah bit 7
I/O 0128h
Memory 0000:04F8h-04FDh
Type 6 BYTES
Name
Classification Undocumented
Target ITF equipped machines,
SCSI BIOS,
98NOTE (excluding PC-9801N/NS/NS/T),
PC-9821Bp/Bs/Be/Bf, PC-9801BA2/BS2/BX2 equipped IDE BIOS
Contents Work area for storing code when switching banks
Explanation o Used when switching banks from ITF to BIOS, or from BIOS to ITF.
Since ITF and BIOS are located at the same address, when switching banks, the
CPU must execute code in a place where bank switching does not occur. When
switching banks, write the bank switching code (OUT command, etc.) to this
area, execute this area to switch banks, and then return execution to the BIOS or ITF.
o Similarly, this area is used when switching banks in the SCSI BIOS, the
D8000h bank of 98NOTE (excluding PC-9801N, NS, and NS/T), and some IDE BIOSes.
o This area is also used when executing some functions of INT 1Fh of the
PC-H98, because the MENU bank contains code.
Related 0000:04F0h
Memory 0000:04FEh (IDE)
Type WORD
Name
Classification IDE BIOS
Undocumented
Target IDE HDD-equipped machines
Contents Wait counter when starting the IDE HDD motor
Explanation o Used to measure the time it takes for the motor rotation to
stabilize after the IDE BIOS sends a spindle motor start command to the IDE
HDD. BIOS processing does not end until the motor rotation stabilizes.
o The 98NOTE system timer decrements this value. The counter decrement ends at 0000h.
o The IDE BIOS of desktop machines still has a process to clear this area to
zero, but it is not used as a counter.
Related INT 0Eh (External interrupt...98NOTE)
INT 17h (External interrupt...98NOTE)
INT 1Bh - Function D0h (IDE)
INT 1Bh - Function E0h (IDE)
INT 1Bh - Function F0h (IDE)
Memory 0000:04D0h-04EFh (LT/HA)
Type 32 BYTES
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Contents Display area 0-3 parameter storage area
-----------+-----------------------------------------------------
Address | Contents
-----------+-----------------------------------------------------
04D0-04D7h | Display area 0 parameter storage area
04D8-04DFh | Display area 1 parameter storage area
04E0-04E7h | Display area 2 parameter storage area
04E8-04EFh | Display area 3 parameter storage area
-----------+---------------------------------------------------------
Parameter contents
------------+-----------------------------------------------------
Offset | Contents
------------+-----------------------------------------------------
+00h (WORD) | Unknown
+02h (BYTE) | Unknown
+03h (BYTE) | Number of lines
+04h (WORD) | Display start offset address of virtual text VRAM
+06h (WORD) | Unknown
------------+-----------------------------------------------------
Explanation o Storage area for the settings of INT 18h - Function 0Eh, 0Fh
(setting one display area, setting multiple display areas).
o The DB-P1 does not have a screen division function, but this content is
referenced when displaying, just like the PC-98LT/HA.
Related INT 18h - Function 0Eh
INT 18h - Function 0Fh
Memory 0000:04F0h (LT/HA)
Type 8bit FLAGS
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA,DB-P1
Content Cursor drawing control flag
bit 7: Cursor width
1 = Full width
0 = Half width
bit 6-4: Unused
bit 3: Cursor drawing prohibition notification
1 = Cursor drawing prohibited
0 = Cursor drawing permitted
bit 2: Cursor inversion state
1 = Inverted state
0 = Non-inverted state
bit 1: Cursor display state
1 = Cursor displayed
0 = Cursor not displayed
bit 0: Cursor blink state
1 = Blinking
0 = No blinking
Explanation o Work area that stores cursor state.
o Bit 3 becomes 1 when the INT 0Ah handler should not draw the cursor, such as during character writing.
Related INT 0Ah (External interrupt...LT/HA)
INT 18h - Function 10h
INT 18h - Function 11h
INT 18h - Function 12h
Memory 0000:04F1h (LT/HA)
Type BYTE
Name
Classification RS-232C BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Content Copy of memory switch 03h
Explanation o Used to check the value of bit 7 (processing when DEL is received) in the RS-232C BIOS.
u DB-P1 also copies the value of memory switch 03h like PC-98LT/HA, but since
there is no RS-232C BIOS, it is not referenced.
Related Memory switch 03h
Memory 0000:04F2h (LT/HA)
Type WORD
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Contents Cursor position (offset address on virtual text VRAM)
Explanation o INT 18h - Stores the cursor position set by Function 13h.
Related INT 18h - Function 13h
Memory 0000:04F4-04F7h (LT/HA)
Type
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Contents Size and segment address of emulation VRAM
-------------+----------------------------------------------------
Address | Contents
-------------+----------------------------------------------------
04F4h (WORD) | Size of emulation VRAM
04F6h (WORD) | Segment address of emulation VRAM
-------------+----------------------------------------------------
Explanation o Stores the size and segment address of emulation VRAM set and
acquired by INT 18h - Function 25h Subfunction 00h, 01h.
Related INT 18h - Function 25h Subfunction 00h
INT 18h - Function 25h Subfunction 01h
Memory 0000:04F8h (LT/HA)
Type 8bit FLAGS
Name
Classification Undocumented
Target PC-98LT/HA, DB-P1
Content Power control related flags
bit 7:
■PC-98LT
The NMI handler sets this bit to 1 when the power switch is OFF.
■PC-98HA
POWER OFF flag
* The INT 0Ah handler turns the power OFF when this bit is 1.
* The NMI handler sets this bit to 1 when I/O 8810h bit 0=1 (power switch pressed).
* INT 1Fh - Function 98h sets this bit to 1.
■DB-P1
The NMI handler sets this bit to 1 when I/O FECCh bit 4=1.
bit 6:
■PC-98LT
POWER OFF flag
* The INT 0Ah handler turns the power OFF when this bit is 1 (executes INT 1Fh - Function 98h).
* The NMI handler issues INT 1Fh - Function 8Ch when the power switch is OFF.
At this time, if it returns with CF=0, it sets this bit to 1.
* The INT 0Ah handler sets this bit to 1 when the auto power-off time arrives.
■DB-P1
POWER OFF flag
* The INT 0Ah handler turns the power OFF when this bit is 1.
* INT 1Fh - Function 98h sets this bit to 1.
bit 5: Active state flag [PC-98LT･HA, DB-P1]
1 = Active state
0 = Inactive state
* Set to 1 by INT 09h (keyboard interrupt), INT 1Bh (DISK BIOS), INT 0Ch
(RS-232C) handlers, etc. Reset to 0 every second by INT 0Ah handler. The
no-operation alarm and auto power off counters are reset to their initial
values when this bit is 1. They are decremented when this bit is 0.
bit 4: Auto power off flag [DB-P1]
* When auto power off occurs, this becomes 1 together with bit 7 (this byte is 90h).
bit 3: Unused
bit 2: Unused
bit 1: BEEP ON request [PC-98LT･HA]
1 = BEEP ON when the next INT 0Ah occurs
0 = NOP
bit 0: BEEP OFF request [PC-98LT･HA]
1 = BEEP OFF when the next INT 0Ah occurs
0 = NOP
Explanation o Power control related flag.
Related INT 0Ah (External interrupt...LT･HA)
Memory 0000:04F9h (LT/HA)
Type 8bit FLAGS
Name
Classification Undocumented
Target PC-98LT/HA
Contents Work area for alarm control when no operation is performed
bit 7,6: Unused
bit 5: Alarm when no operation is performed
1 = Alarm is sounding
0 = Alarm is not sounding
bit 4: Unknown
bit 3-0: Beep-related counter
Explanation o Details unknown.
Related
Memory 0000:04FAh (LT/HA)
Type BYTE
Name
Classification Undocumented
Target PC-98LT/HA, DB-P1
Contents Round-robin counter for INT 0Ah handler
Explanation o ■PC-98LT
A counter for executing 10 types of processing in the INT 0Ah handler at 1-second intervals.
Decremented at 10Hz intervals. Repeats 9,8,...,1,0,9,....
o ■PC-98HA
A counter for executing 10 types of processing in the INT 0Ah handler at 1 second intervals.
Decrements at 40Hz intervals. Repeats 39,38,...,1,0,39,..., executing 10 types
of processing in sequence, once every 4 times.
o ■DB-P1
A counter for executing 2 types of processing in the INT 0Ah handler at intervals of
approximately 1 second or approximately 0.5 seconds. Decrements at 15.8Hz intervals.
Related INT 0Ah (External interrupt...LT･HA)
Memory 0000:04FBh (LT/HA)
Type BYTE
Name
Classification Undocumented
Target PC-98LT/HA, DB-P1
Contents 1-minute counter for INT 0Ah handler
Explanation o Down counter for processing executed every minute in INT 0Ah handler.
Decremented at 1Hz. Repeats 59, 58, ..., 1, 0, 59, ....
Used to decrement the no-operation alarm counter and auto power off counter.
Related 0000:04FCh
0000:04FDh
INT 0Ah (External interrupt...LT/HA)
Memory 0000:04FCh (LT/HA)
Type BYTE
Name
Classification Undocumented
Target PC-98LT/HA
Contents No operation alarm counter (unit: minutes)
Explanation o When active (0000:04F8h bit 5=1), the value of memory switch 18h
is copied. When inactive (0000:04F8h bit 5=0), this value is decremented every
minute. When it reaches 0, a buzzer sounds. If any operation is performed, this
value returns to the initial value (the value of memory switch 18h).
This function does not work when the original value is 0.
o Not used for DB-P1.
Related 0000:04F8h bit 5
0000:04FBh
Memory 0000:04FDh (LT/HA)
Type BYTE
Name
Classification Undocumented
Target PC-98LT/HA, DB-P1
Contents Auto power off counter (unit: minutes)
Explanation o When active (0000:04F8h bit 5=1), the value of memory switch 19h
is copied. When inactive (0000:04F8h bit 5=0), this value is decremented every
minute. When it becomes 0, the power is turned off.
When the original value is 0, this function does not work.
u In PC-98LT, the auto power off function itself is not disclosed.
o In DB-P1, when INT 1Fh - Function 9Bh is executed, the value of memory switch 19h is copied.
Related 0000:04F8h bit 5
0000:04FBh
INT 1Fh - Function 9Bh (DB-P1)
Memory 0000:04FEh (LT/HA)
Type WORD
Name
Classification Undocumented
Target PC-98LT/HA
Contents 10Hz 16-bit down counter of INT 0Ah
Explanation o When this value is other than 0000h, the INT 0Ah handler
decrements at 10Hz intervals. When it reaches 0000h, the decrement stops.
o The BIOS does not seem to perform any processing that references this value.
Related INT 0Ah (External interrupt...LT/HA)
Memory 0000:0500h
Type 8bit FLAGS
Name BIOS_FLAG
・bit 7
Classification
Target Normal, High Resolution, PC-98LT/HA
Contents Startup type
1 = Hot start
0 = Cold start
Explanation o Becomes 1 when the system is started after resetting while pressing the STOP key.
Related
・bit 6
Classification
Target Normal, PC-98LT/HA
Contents BASIC type
1 = DISK BASIC, MS-DOS version BASIC running and its child processes
0 = ROM BASIC, MS-DOS, other OS running
Explanation o Indicates the type of BASIC being run.
Related
・bit 5
Classification KEYBOARD BIOS
Target Normal, High Resolution, PC-98LT/HA
Contents Key buffer overflow notification control
1 = Do not beep when key buffer overflows
0 = Beep when key buffer overflows (default)
Explanation o Sets whether to sound a warning beep when the keyboard buffer overflows.
Related
・bit 4
Classification MEMORY
Target Normal
Contents Presence or absence of additional RAM within addresses 00000-9FFFFh (640KB-1)
1 = Yes
0 = No
Explanation o Becomes 1 when additional RAM is installed in the expansion slot within addresses 00000-9FFFFh (640KB-1).
Related
・bit 3
Classification Undocumented
Target
Content Unused
Explanation o Some documents state that this bit becomes 1 during VSYNC, but in reality,
the BIOS uses 0000:053Ch bit 6 for VSYNC processing.
Related
・bit 2
Classification DISK BIOS
Target Dual-use BIOS - 640KB I/F mode
Content Dual-use FD I/F - Presence or absence of AI in 640KB I/F mode
1 = AI Enable
0 = AI Disable
Explanation o This bit can be set and read by the DISK BIOS, but cannot be cleared.
Related INT 1Bh - Function 83h(FD)
INT 1Bh - Function 84h(FD)
・bit 1
Classification DISK BIOS
Target Dual-use BIOS + Normal
Content Dual-use FD I/F mode
1 = 1MB I/F mode
0 = 640KB I/F mode
Explanation o The dual-use FD I/F in high-resolution mode is fixed to 1MB I/F mode.
o The dual-use FD I/F in PC-98LT･HA,DB-P1 is fixed to 640KB I/F mode.
Related
・bit 0
Classification Model discrimination
Target All models
Content Model information(1)
1 = Other
0 = PC-9801 first generation･E･F･M, PC-98LT･HA, DB-P1, high-resolution mode
Explanation o In combination with other bits, the following model discrimination can be performed.
------------------+----------------------------------
Model information | Meaning
(1)(2)(3)(4) |
------------------+----------------------------------
0 0 0 0 | PC-9801 original
0 1 0 0 | PC-9801E･F･M
1 1 1 0 | PC-9801U
1 1 0 0 | Normal (other than PC-9801 original･E･F･M･U)
0 0 0 1 | PC-98XA
0 1 0 1 | High-resolution (other than PC-98XA)
0 1 1 0 | PC-98LT･HA,DB-P1
------------------+----------------------------------
Model information (1) = 0000:0500h bit 0
Model information (2) = 0000:0501h bit 5
Model information (3) = 0000:0501h bit 4
Model information (4) = 0000:0501h bit 3
Related 0000:0501h bit 5-3
Memory 0000:0501h
Type 8bit FLAGS
Name BIOS_FLAG
・bit 7
Classification
Target All models
Contents System clock frequency
1 = 8MHz
0 = 5MHz,10MHz
Explanation o Indicates the frequency of the clock supplied to the timer (8251A) and the SCLK1 signal of the expansion slot.
o The exact timer clock frequency is as follows.
------+--------------------
Value | Timer clock frequency
------+--------------------
1 | 1.9968MHz
0 | 2.4576MHz
------+--------------------
o The frequency of the SCLK1 signal of the expansion slot is as follows.
------+--------------------
Value | SCLK1 frequency
------+--------------------
1 | 7.9872MHz
0 | 9.8304MHz (other than PC-9801 first generation, E, F, M)
0 | 4.9152MHz (PC-9801 first generation, E, F, M)
------+--------------------
u For most models with a CPU clock of 12MHz or higher, the system clock frequency and CPU clock frequency are unrelated.
Related
・bit 6
Classification CPU discrimination
Target All models
Content CPU type
1 = V30, V30HL, V50, V50HL, V33, V30 equivalent mode
0 = i8086, i80286, i386, i486, Pentium
Explanation o Indicates the operating CPU. However, this bit will also be 1 when a model without a V30 is set to V30 equivalent mode.
Related CPU identification
・bit 5-3
Classification Model identification
Target All models
Contents Model information (2-4)
bit 5: Model information (2)
1 = Other
0 = PC-9801 original, PC-98XA
bit 4: Model information (3)
1 = PC-9801U, PC-98LT･HA, DB-P1
0 = Other
bit 3: Model information (4)
1 = Hi-res mode
0 = Normal mode, PC-98LT･HA, DB-P1
Explanation o 0000:0500h See bit 0.
Related 0000:0500h bit 0
・bit 2〜0
Classification MEMORY
Target All models
Contents Real mode memory size
101b = 768KB
100b = 640KB
011b = 512KB
010b = 384KB
001b = 256KB
000b = 128KB
Explanation o Indicates the RAM capacity located at addresses 00000〜9FFFFh (normal mode)/00000〜BFFFFh (high-resolution mode).
o The size of memory for protected mode is stored in 0000:0401h and 0000:0594h.
Related 0000:0401h
0000:0594h
Memory 0000:0502-0521h
Type 32 BYTES
Name KB_BUF (normal), KB_KEY_BUFFER (high-resolution)
Classification KEYBOARD BIOS
Target All models
Contents Key buffer
Explanation o FIFO type buffer that stores up to 16 sets of 2-byte information on entered keys.
The INT 09h handler processes the data received from the keyboard I/F and
writes it to this area. The keyboard BIOS (INT 18h) retrieves the data from
this area.
o In high-resolution, this is the default key buffer at startup.
Related 0000:0410h [Hi-Res]
INT 09h (External Interrupt)
INT 18h - Function 00h
Memory 0000:0522-0523h
Type WORD
Name KB_SHIFT_TBL
Category KEYBOARD BIOS
Target Normal, PC-98LT/HA, DB-P1
Contents Key code conversion table offset
Explanation o Stores the offset of the key code conversion table according to the current shift state.
The segment of the key code conversion table is the same as the code conversion table pointed to by 0000:05C6h.
o The INT 09h handler rewrites it along with the ON/OFF of [SHIFT], [CTRL], [CAPS], [GRPH], and [Kana]. Used to convert key codes to key data.
Related 0000:05C6h
INT 09h (External interrupt)
Memory 0000:0522h
Type BYTE
Name KB_BUFFER_SIZ
Category KEYBOARD BIOS
Target Hi-Res
Content Key buffer size
Initial value = 10h
Explanation o The number of key information (2-byte set) that can be stored in the key buffer. The buffer must be twice the size of the value specified in this byte.
Related 0000:0410h
INT 09h (External interrupt)
INT 18h - Function 06h
Memory 0000:0524-0525h
Type WORD
Name KB_BUF_HEAD (normal), KB_HEAD_POINTER (high-res)
Category KEYBOARD BIOS
Target All models
Contents Key buffer read pointer
Explanation o First offset address of the stored area of the key buffer.
o In high-res, the segment is the same as the segment pointed to by 0000:0410h (KB_BUF_ADR).
Related 0000:0410h [high-res]
0000:0502h
INT 09h (external interrupt)
Memory 0000:0526-0527h
Type WORD
Name KB_BUF_TAIL (normal), KB_TAIL_POINTER (high-res)
Category KEYBOARD BIOS
Target All models
Contents Key buffer write pointer
Explanation o Last offset address of the stored area of the key buffer +2.
o In high-res mode, the segment is the same as the segment pointed to by 0000:0410h (KB_BUF_ADR).
Related 0000:0410h [High-res]
0000:0502h
INT 09h (External interrupt)
Memory 0000:0528h
Type BYTE
Name KB_COUNT (Normal), KB_BUFFER_COUNTER (High-res)
Classification KEYBOARD BIOS
Target All models
Content Number of data in key buffer
Explanation o Number of data stored in the key buffer.
Related 0000:0410h [Hi-Res]
0000:0502h
INT 09h (External Interrupt)
Memory 0000:0529h
Type BYTE
Name KB_RETRY (Normal), KB_RETRY_COUNTER (Hi-Res)
Classification KEYBOARD BIOS
Target All models
Content Keyboard I/F receive error retry count
Explanation o If an error is detected when the INT 09h handler receives data from the keyboard I/F, it requests
the keyboard to resend the data. The INT 09h handler requests resend up to three times, and if an
error still occurs, it processes the received data as is.
Related INT 09h (External Interrupt)
I/O 0041h
Memory 0000:052A-0539h
Type 16 BYTES
Name KB_KY_STS (normal), KB_KEY_STS_TBL (high resolution)
Category KEYBOARD BIOS
Target All models
Contents Key press status table
-----+-------+-------+-------+-------+-------+-------+-------+-------
ｱﾄﾞﾚｽ|bit 7 |bit 6 |bit 5 |bit 4 |bit 3 |bit 2 |bit 1 |bit 0
-----+-------+-------+-------+-------+-------+-------+-------+-------
052Ah|7' |6& |5% |4$ |3# |2" |1! |ESC
|ﾔｬ |ｵｫ |ｴｪ |ｳｩ |ｱｧ |ﾌ |ﾇ |
052Bh|TAB |BS |¥| |^` |-= |0 |9) |8(
| | |ｰ |ﾍ |ﾎ |ﾜｦ |ﾖｮ |ﾕｭ
052Ch|I |U |Y |T |R |E |W |Q
|ﾆ |ﾅ |ﾝ |ｶ |ｽ |ｲ |ﾃ |ﾀ
052Dh|D |S |A |ﾘﾀｰﾝ |[{ |@‾ |P |O
|ｼ |ﾄ |ﾁ | | | |ｾ |ﾗ
052Eh|:* |;+ |L |K |J |H |G |F
|ｹ |ﾚ |ﾘ |ﾉ |ﾏ |ｸ |ｷ |ﾊ
052Fh|M |N |B |V |C |X |Z |}]
|ﾓ |ﾐ |ｺ |ﾋ |ｿ |ｻ |ﾂｯ |ﾑ｣
0530h|ROLL |ROLL |XFER |ｽﾍﾟｰｽ |_ |/? |.> |,<
|DOWN |UP | | |ﾛ |ﾒ･ |ﾙ｡ |ﾈ｡
0531h|HELP |HOME |↓ |→ |← |↑ |DEL |INS
| |CLR | | | | | |
0532h|5 |4 |* |9 |8 |7 |/ |-
| | | | | | | |
0533h|, |0 |= |3 |2 |1 |+ |6
| | | | | | | |
0534h| |vf･5 |vf･4 |vf･3 |vf･2 |vf･1 |NFER |.
| | | | | | | |
0535h| |HOME | |子音ｼﾌﾄ|母音ｼﾌﾄ|記号ｼﾌﾄ|NUM |
| | | | | | | |
0536h|f･6 |f･5 |f･4 |f･3 |f･2 |f･1 |COPY |STOP
| | | | | | | |
0537h| | | | |f･10 |f･9 |f･8 |f･7
| | | | | | | |
0538h| | | |CTRL |GRPH |カナ |CAPS |SHIFT
| | | | | | | |
0539h| | | | | | | |
-----+-------+-------+-------+-------+-------+-------+-------+-------
* The bit corresponding to the pressed key becomes 1.
* [Consonant Shift], [Vowel Shift], [Symbol Shift], and [NUM] are only available in the PC-9801-98
(Easy Keyboard) "Automatic Conversion Mode". The pressed state of the [NUM] key, such as NOTE,
is not reflected in this table.
Explanation o Indicates the current pressed state of the key, regardless of the key buffer. The INT 09h handler
sets/resets the bits in this table based on the data read from the keyboard I/F 8251A.
INT 18h - Function 04h (sense of key input state) returns the value of this table.
u PC-9800 keyboards repeat when pressed, so there are periods when the bits in this table become 0 even
though the key is pressed. Note that shift keys, function keys, and the [INS] key do not repeat.
The keyboard edition of "PC-9801 Super Techniques" (published by ASCII Publishing Bureau) has a detailed
description of repeat.
o When pressing a key that is not originally provided for the model (such as pressing the vf key on a
model for old keyboards with a new keyboard), no data is stored in the key buffer, but the pressed
state is reflected in this table.
o In high-resolution mode, even if the shift key code table (0000:0408-040Fh) or the key data conversion
table (address pointed to by 0000:0414h) is changed, it does not affect the operation indicated by this table.
Related INT 09h (External Interrupt)
INT 18h - Function 04h
Memory 0000:053Ah
Type 8bit FLAGS
Name KB_SHFT_STS (Normal), KB_SHIFT_STS (Hi-Res)
Category KEYBOARD BIOS
Target All models
Content Shift key pressed status flag
bit 7:
bit 6:
bit 5:
bit 4: [CTRL]
bit 3: [GRPH]
bit 2: [Kana]
bit 1: [CAPS]
bit 0: [SHIFT]
1 = Pressed
0 = Not pressed
Explanation o Indicates the current pressed status of the shift keys ([CTRL], [GRPH], [Kana], [CAPS], [SHIFT]). Set/reset by INT 09h handler.
INT 18h - Function 02h (Sense of shift key status) returns this value.
o In the case of high resolution, when a key registered in the shift key code table (0000:0408-040Fh) is pressed, the corresponding bit becomes 1.
Related 0000:0408-040Fh [High Resolution]
INT 09h (External Interrupt)
INT 18h - Function 02h
Memory 0000:053Bh
Type BYTE
Name CRT_RASTER
Category CRT BIOS
Target Normal, High-Resolution
Content Number of rasters per line of text screen - 1
Table Screen status and corresponding setting
---------------+-----------------+---------------+-----------------+----------+-------------------------
CRT resolution | Horizontal scan | Vertical sync | Text | Raster | Notes
| Frequency | Frequency | Number of lines | Number-1 |
---------------+-----------------+---------------+-----------------+----------+-------------------------
640x200 | 15.98kHz | 61.47Hz | 20 | 09h | *1
↑ | ↑ | ↑ | 25 | 07h |
640x400 | 24.83kHz | 56.42Hz | 20 | 13h | *2
↑ | ↑ | ↑ | 25 | 0Fh |
640x400 | 31.47kHz | 70.10Hz | 20 | 13h | *3
↑ | ↑ | ↑ | 25 | 0Fh |
640x480 | 31.47kHz | 59.94Hz | 20 | 17h | *4
↑ | ↑ | ↑ | 25 | 12h |
↑ | ↑ | ↑ | 30 | 0Fh |
1120x750 | 32.86kHz | 79.09Hz | 25 | 0Eh | *5
↑ | ↑ | ↑ | 31 | 0Bh |
1120x750 | 50.02kHz | 60.05Hz | 25 | 1Dh | *6
↑ | ↑ | ↑ | 31 | 17h |
640x480 | 15.73kHz | 59.94Hz | 20 | 09h | *7 When graphic resolution is 640x400
↑ | ↑ | ↑ | 20 | 0Bh | When graphic resolution is 640x480
↑ | ↑ | ↑ | 25 | 07h | When graphic resolution is 640x400
↑ | ↑ | ↑ | 30 | 07h | When graphic resolution is 640x480
---------------+-----------------+---------------+-----------------+----------+-------------------------
*1: CRT signal when DIP SW 1-1 is turned OFF on models with digital RGB output.
Setting when connecting a PC-8001 display.
*2: The most standard CRT signal in normal mode.
*3: Normal mode CRT signal when [GRPH]+[2]+[RESET] is set on PC-9821 (except the original, Ne, Np, Ce, Ts), PC-9801BA2,
BS2, BX2, BA3, BX3, BX4, and when an N5926-01 or 02 type display is connected to a PC-H98 and 25 lines with space
between lines is not displayed. PC-9821Ce can be set in the BIOS. PC-9821Ne, Np, Ts cannot be set.
*4: Normal mode CRT signal when displaying 640x480 on PC-9821 (except Bp, Bs, Be, Bf, Ts, Ne3, Nd2), PC-98GS, and when
an N5926-01 or 02 type display is connected to a PC-H98 and 25 lines with space between lines are displayed.
*5: CRT signal (interlaced) when the [GRPH]+[1]+[RESET] setting is made in the high-resolution mode of PC-98XA/XL/RL,
high-resolution mode when an N5926-01 display is connected to a PC-H98, and high-resolution mode of the 98
high-resolution board (PC-9821A-E02).
*6: CRT signal (non-interlaced) when the [GRPH]+[2]+[RESET] setting is made in the high-resolution mode when an N5926-02
display is connected to a PC-H98, and high-resolution mode of the 98 high-resolution board (PC-9821A-E02).
*7: CRT signal when set to video mode on a PC-98GS. It cannot be distinguished from the state of a vertical sync frequency
of 56.42Hz from the state of the system common area.
Explanation o Indicates the value of the number of rasters for one line of the text screen minus 1.
If you change the number of lines on the text screen in the CRT BIOS, this value will also change.
o PC-98LT-HA and DB-P1 do not use this address.
Related 0000:0452h [Hi-Res]
INT 0Ah (External interrupt...VSYNC)
INT 18h - Function 0Ah
INT 18h - Function 11h
INT 18h - Function 12h
INT 18h - Function 30h
Memory 0000:053Ch
Type 8bit FLAGS
Name CRT_STS_FLAG
Category CRT BIOS
Target Normal
Contents Text screen status flag
bit 7: CRT type
1 = Dedicated high-resolution display (when booting with DIP SW 1-1 ON)
0 = Standard display (when booting with DIP SW 1-1 OFF)
* 0 when outputting CRT signal for PC-8001 display (horizontal scan frequency = 15.98kHz,
vertical sync frequency = 61.47Hz). 1 when outputting other CRT signals.
Related 0000:054Ch bit 6
INT 0Ah (External interrupt...VSYNC)
DIP SW 1-1
bit 6: VSYNC detected (Undocumented)
1 = Waiting for VSYNC
0 = VSYNC internal processing completed
* INT 18h - Used in the VSYNC wait routine of Function 0Ah, 0Eh, 0Fh, 10h, 14h, 1Ah, 1Ch, 1Dh, 1Eh, 1Fh, 20h.
When performing processing synchronized with VSYNC in the BIOS, such as reading a font, the interrupt processing
routine uses this bit to notify the end of processing. For example, when reading a font, the actual reading is
performed in the VSYNC interrupt processing routine. When processing in the interrupt routine is completed,
this bit is set to 0 to notify the main routine. The main routine recognizes the end of processing by continuously
checking this flag.
Related 0000:0500h bit 3
bit 5: Unused
bit 4: Number of lines [PC-98GS, PC-9821 (excluding Bf, Bp, Bs, Be, Ts, Ne3, Nd2)] (Undocumented)
1 = 30 lines
0 = 20/25 lines (initial setting)
bit 3: K-CG (Kanji character generator) access mode
1 = Dot access
0 = Code access (initial setting)
* Disabled on the original PC-9801 (always in code access state)
bit 2: Attribute mode
1 = Simple graphics (initial setting)
0 = Vertical lines
* The initial value set by the BIOS is simple graphics mode, but after MS-DOS starts, it is set to vertical line mode.
bit 1: Number of digits
1 = 40 digits (startup setting when DIP SW 2-3 is OFF)
0 = 80 digits (startup setting when DIP SW 2-3 is ON)
bit 0: Number of lines
1 = 20/30 lines
0 = 25 lines
------+-------+-----------------+------------------------------------
bit 4 | bit 0 | Number of lines | Notes
------+-------+-----------------+------------------------------------
0 | 1 | 20 lines | Startup setting when DIP SW 2-4 is OFF
0 | 0 | 25 lines | Startup setting when DIP SW 2-4 is ON
1 | 1 | 30 lines | Can only be set when displaying 640x480
1 | 0 | --- | Unused
------+-------+-----------------+------------------------------------
Explanation o INT 18h - Storage area for setting values of Function 0Ah (normal) and 0Bh (normal).
Bits 4 and 0 also change if you change the number of rows with INT 18h - Function 30h.
o High-resolution mode does not use this address.
Related INT 18h - Function 0Ah (Normal)
INT 18h - Function 0Bh (Normal)
INT 18h - Function 30h
INT 18h - Function 31h
Memory 0000:053Ch(LT･HA)
Type 8bit FLAGS
Name
Classification CRT BIOS
Undocumented
Target PC-98LT･HA
Contents Text screen status flag
bit 7: Character type
1 = 88 type characters (initial state)
0 = 80 type characters
bit 6-1: Unused
bit 0: Number of display lines
1 = 20 lines
0 = 25 lines
Explanation o INT 18h - Function 0Ah(LT･HA),0Bh(LT･HA) setting value storage area.
u The display character font can be selected with bit 7, but it cannot be
changed with INT 18h - Function 0Ah(LT･HA). After directly manipulating this
work area to set bit 7=1, it can be changed by executing INT 18h - Function 0Ah(LT･HA).
u When set to 80 type characters, characters will only be displayed in the upper half of
the screen. Kanji characters will not be displayed correctly (only the top half of the kanji will be displayed).
Related INT 18h - Function 0Ah (LT/HA)
INT 18h - Function 0Bh (LT/HA)
Memory 0000:053Ch (DB-P1)
Type 8bit FLAGS
Name
Classification CRT BIOS
Undocumented
Target DB-P1
Contents Text screen status flag
bit 7: Unused (always set to 1 by BIOS)
bit 6: Screen inversion status
1 = Inverted display (a dot with a value of 1 on the VRAM is displayed in white)
0 = Normal display (a dot with a value of 1 on the VRAM is displayed in black)
bit 5: Display page selection
1 = Plane 1 (used for DB menu)
0 = Plane 0 (for application)
bit 4: Active page selection
1 = Plane 1 (used for DB menu)
0 = Plane 0 (for application)
bit 3-0: Unused (always set to 0010b internally)
Explanation o INT 18h - Function 0Ah(DB-P1), 0Bh(DB-P1) setting value storage area.
Related INT 18h - Function 0Ah(DB-P1)
INT 18h - Function 0Bh(DB-P1)
Memory 0000:053Dh
Type BYTE
Name CRT_CNT
Category CRT BIOS
Target Normal, Hi-Res
Contents CRT BIOS work area
Explanation o In normal mode, INT 18h - Function 0Fh, 10h, 14h is used as the work area.
In Hi-Res mode, INT 18h - Function 0Fh, 1Dh is used as the work area.
o 07h is set in PC-98LT-HA and DB-P1, but is not used in BIOS.
Related
Memory 053E-0541h
Type DWORD
Name CRT_OFST (normal), CRT_SEG_ADR (hi-res)
Category CRT BIOS
Target Normal, Hi-Res
Contents CRT BIOS work area
Explanation o In normal mode, INT 18h - Function 0Fh, 14h, 1Ah is used as the work area.
In high-resolution mode, this is used as a work area by INT 18h - Function 0Fh, 1Fh, 20h.
Related
Memory 0542-0545h
Type DWORD
Name CRT_V_INT_OFST/SEG
Classification CRT BIOS
Target Normal, high-resolution
Contents VSYNC interrupt (INT 0Ah) vector save area
Explanation o Area to save the address of the original INT 0Ah vector when waiting for a VSYNC (INT 0Ah) interrupt in CRT BIOS.
o In normal mode, this is used by INT 18h - Function 0Eh, 0Fh, 10h, 14h, 1Ah.
In high-resolution mode, this is used by INT 18h - Function 0Ah, 0Eh, 0Fh, 10h, 1Ch, 1Dh, 1Eh, 1Fh, 20h.
Related INT 0Ah (External interrupt...VSYNC)
Memory 053E-0545h (LT/HA)
Type 8 bytes
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Contents Work area related to screen display
-------------+----------------------------------------------------
Address | Contents
-------------+----------------------------------------------------
053Eh (WORD) | Unknown
0540h (WORD) | Number of dots vertically per character (for cursor inversion)
0542h (WORD) | Number of bytes per line on graphic VRAM
0544h (WORD) | Number of dots vertically per character (use unknown)
-------------+----------------------------------------------------
■Settings by mode
--------+--------------------+---------------------
| 88 type characters | 80 type characters
+----------+----------+----------+---------
Address | 25 lines | 20 lines | 25 lines | 20 lines
--------+----------+----------+----------+---------
0540h | 0010h | 0014h | 0008h | 000Ah
0542h | 0500h | 0640h | 0280h | 0320h
0544h | 0010h | 0014h | 0008h | 000Ah
--------+----------+----------+----------+---------
* 88 type characters are when 0000:053Ch bit 7=1
* 80 type characters are when 0000:053Ch bit 7=0
* DB-P1 only supports 88 type characters, 25 lines mode.
Explanation u INT 18h - Function 0Ah(LT･HA), 0Ah(DB-P1) sets the value.
Related INT 18h - Function 0Ah(LT･HA)
INT 18h - Function 0Ah(DB-P1)
Memory 0000:0546h (Normal)
Type BYTE
Name CRT_FONT
Classification CRT BIOS
Target Normal
Contents CRT BIOS work area
■Other than the first generation PC-9801
bit 7-3: Unused
bit 3: Full-width flag
1 = 16x16 dot character
0 = Other than 16x16 dot character
bit 2: 2-byte half-width flag
1 = 8x16 dot character (2-byte half-width)
0 = Other than 8x16 dot character (2-byte half-width)
bit 1: 88 type ANK flag
1 = 7x13 dot character
0 = Other than 7x13 dot character
bit 0: 80 type ANK flag
1 = 6x7 dot character
0 = Other than 6x7 dot character
■First generation PC-9801
bit 1: Kanji/ANK
1 = Kanji font
0 = ANK font
bit 0 : Font size
1 = 7x11 font
0 = 6x7 font
Description o Used as the work area for INT 18h - Function 14h (reading font patterns).
o PC-98LT-HA, DB-P1 do not use this address.
Related INT 18h - Function 14h
Memory 0000:0546h (Hi-Res)
Type 8bit FLAGS
Name CRT_FLAG
Category CRT BIOS
Target Hi-Res
Contents Text screen status flag
bit 7: VSYNC detected
1 = VSYNC processing completed
0 = VSYNC waiting state
* INT 18h - Function Used in the VSYNC waiting routine of 0Ah, 0Eh, 0Fh, 10h, 1Ch, 1Dh, 1Eh, 1Fh, 20h.
When performing processing synchronized with VSYNC in the BIOS, such as reading a font, the interrupt
processing routine uses this bit to notify the end of processing.
For example, when reading a font, the actual reading is performed in the VSYNC interrupt processing
routine. When processing in the interrupt routine is completed, this bit is set to 1 to notify the main
routine. The main routine recognizes the end of processing by continuously checking this flag.
bit 6: Buzzer status
1 = Buzzer ringing with INT 18h - Function 17h
0 = Buzzer not ringing with INT 18h - Function 17h
* This becomes 1 when the buzzer is ringed with INT 18h - Function 17h (ringing the buzzer),
and becomes 0 when INT 18h - Function 18h (stopping the buzzer) is executed.
When executing INT 18h - Function 24h (buzzer time setting and ringing) or
INT 1Ch - Function 06h (beep function) to stop the buzzer after a certain
period of time, this is used to prevent the buzzer from stopping if the buzzer
is ON with INT 18h - Function 17h.
Related INT 18h - Function 17h
INT 18h - Function 18h
bit 5: Unused
bit 4: Number of display lines
1 = 31 lines
0 = 25 lines (initial setting)
Related INT 18h - Function 0Ah (Hi-Res)
INT 18h - Function 0Bh (Hi-Res)
bit 3: KCG access mode
1 = Dot access
0 = Code access (initial setting)
Related INT 18h - Function 0Ah (Hi-Res)
INT 18h - Function 0Bh (Hi-Res)
bit 2: Unused
bit 1: Unused
bit 0: Font type
1 = Full-width
0 = Half-width, ANK
* Work area for INT 18h - Function 1Fh (Reading font pattern (24 dots)).
Explanation o INT 18h - Function 0Ah (Hi-Res), 0Bh (Hi-Res) setting value storage area, and CRT BIOS work area.
Related
Memory 0000:0547h
Type BYTE
Name CRT_WINDOW_NO
Category CRT BIOS
Target Normal, High Resolution
Contents CRT BIOS work area
Explanation o INT 18h - Used as the work area for Function 0Fh (setting multiple display areas).
The number of partial screens (scroll areas) to be set in the GDC is stored.
o PC-98LT-HA, DB-P1 do not use this address.
Related INT 18h - Function 0Fh
Memory 0000:0548-0549h
Type WORD
Name CRT_W_VRAMADR
Category CRT BIOS
Target Normal, High Resolution
Contents CRT BIOS work area
Explanation o INT 18h - Used as the work area for Function 0Eh (setting one display area).
The first and second parameters when issuing the SCROLL command to the GDC.
This holds the display start offset address of the text VRAM seen by the GDC.
o PC-98LT-HA, DB-P1 do not use this address.
Related INT 18h - Function 0Eh
Memory 0000:054A-054Bh
Type WORD
Name CRT_W_RASTER
Category CRT BIOS
Target Normal, High-Res
Contents CRT BIOS work area
Table Screen status and corresponding setting values
---------------+-----------------+---------------+--------------+-------------------------
CRT resolution | Horizontal scan | Vertical sync |Setting value | Notes
| Frequency | Frequency | |
---------------+-----------------+---------------+--------------+-------------------------
640x200 | 15.98kHz | 61.47Hz | 0C80h | *1
640x400 | 24.83kHz | 56.42Hz | 1900h | *2
640x400 | 31.47kHz | 70.10Hz | 1900h | *3
640x480 | 31.47kHz | 59.94Hz | 1900h | *4
1120x750 | 32.86kHz | 79.09Hz | 0177h | *5
1120x750 | 50.02kHz | 60.05Hz | 03FFh | *6
640x480 | 31.47kHz | 59.94Hz | 3FF0h | *7
640x480 | 15.73kHz | 59.94Hz | 1900h | *8 When graphic resolution is 640x400
↑ | ↑ | ↑ | 3FF0h | When graphic resolution is 640x480
---------------+-----------------+---------------+--------------+-------------------------
*1: Models with digital RGB output, DIP SW CRT signal when 1-1 is turned OFF. Settings when connecting a PC-8001 display.
*2: The most standard CRT signal in normal mode.
*3: The CRT signal in normal mode when [GRPH]+[2]+[RESET] is set on the PC-9821 (except the original, Ne, Np, Ce, Ts),
PC-9801BA2, BS2, BX2, BA3, BX3, BX4, and when an N5926-01 or 02 type display is connected to a PC-H98 and 25 lines
of space are not displayed.
*4: The CRT signal in normal mode when displaying 640x480 on the PC-9821 (except Bp, Bs, Be, Bf, Ts, Ne3, Nd2), and when
an N5926-01 or 02 type display is connected to a PC-H98 and 25 lines of space are displayed.
*5: CRT signal (interlaced) when the [GRPH]+[1]+[RESET] settings are made in high-resolution mode for PC-98XA/XL/RL,
high-resolution mode when an N5926-01 display is connected to a PC-H98, and high-resolution mode for the 98 Hi-Res
Board (PC-9821A-E02).
*6: CRT signal (non-interlaced) when the [GRPH]+[2]+[RESET] settings are made in high-resolution mode when an N5926-02
display is connected to a PC-H98, and high-resolution mode for the 98 Hi-Res Board (PC-9821A-E02).
*5: CRT signal when the PC-98GS is in 640x480 display (non-video mode).
*7: CRT signal when the PC-98GS is set to video mode.
Description o INT 18h - Used as the work area for Function 0Eh (setting one display area).
The third and fourth parameters when issuing a SCROLL command to the GDC. The
number of rasters on the entire display screen is stored.
o In normal mode, it is stored in the same format as when issued to the GDC,
so the number of rasters is the value shifted 4 bits to the right. In
high-resolution mode, this value directly indicates the number of rasters.
However, it appears to be used for different purposes when displaying at
640x480 dots and when non-interlacing high-resolution.
o PC-98LT-HA and DB-P1 do not use this address.
Related
Memory 0000:054Ch (Normal)
Type 8bit FLAGS
Name PRXCRT
Classification GRAPH BIOS
Target Normal
Content Graphic screen status flag
bit 7: Graphic screen status
1 = Display
0 = Display stopped (startup setting)
Related INT 18h - Function 40h
INT 18h - Function 41h
bit 6: CRT type
1 = High resolution CRT (88 type) (initial state at startup with DIP SW 1-1 ON)
0 = Standard CRT (80 type) (initial state at startup with DIP SW 1-1 OFF)
* 0 when outputting CRT signal for PC-8001 display (horizontal scan frequency = 15.98kHz,
vertical sync frequency = 61.47Hz). 1 when outputting other CRT signals.
Related 0000:053Ch bit 7
INT 0Ah(External interrupt...VSYNC)
DIP SW 1-1
bit 5: Horizontal scan frequency [PC-9821 (except the first generation), PC-H98]
------+----------------+---------------------------+------------------------
Value | CRT resolution | Horizontal scan frequency | Vertical sync frequency
------+----------------+---------------------------+------------------------
0 | 640x400 | 24.83kHz | 56.42Hz
1 | 640x400 | 31.47kHz | 70.10Hz
1 | 640x480 | 31.47kHz | 59.94Hz
------+----------------+---------------------------+------------------------
* On the first generation PC-9821, this remains 0 even in 31.47kHz mode.
On all other models, this is always 0. PC-98GS is also not supported.
Related INT 18h - Function 2Ah
INT 18h - Function 30h
bit 4: CRT line mode [PC-H98]
1 = 640x480 dots
0 = 640x400 dots (initial setting)
* When the horizontal scan frequency is 31kHz in normal mode on the PC-H98
(bit 5 = 1), 640x480 dots (25 lines with space between lines) can be displayed.
Related INT 18h - Function 2Ah
bit 3: Number of user-defined characters
1 = 188 characters (or more)
0 = 63 characters
* The original PC-9801 does not support user-defined characters, PC-9801E/F/M/U can use 63 characters,
PC-H98 can use 219 characters, and others can use 188 characters.
Related INT 18h - Function 1Ah
INT 18h - Function 1Ah (H98)
bit 2: Extended G-VRAM (16-color display G-VRAM)
1 = Yes
0 = No
* Indicates whether or not the 16-color display G-VRAM from E0000 to E7FFFh is present.
Models other than the PC-9801 first generation, E, F, and M can be equipped with an extended G-VRAM or come standard with it.
Related I/O 006Ah - 00h,01h
bit 1: Graphics charger (GRCG)
1 = Yes
0 = No
* Indicates whether or not the GRCG is present. The PC-9801 first generation, E, F, and M cannot be equipped with a GRCG.
Optional for the PC-9801U. Standard for other models.
Related I/O 007Ch
I/O 007Eh
bit 0: DIP SW 1-8 [Excluding the original PC-9801, E, F, and M]
1 = ON
0 = OFF
* Indicates the state of DIP SW 1-8 at startup. Since the state of the DIP-SW at startup is simply copied, this bit alone cannot be used to determine
whether the Graph LIO supports 16-color mode. If 0000:0480h bit 6=1 and 0000:054Ch bit 0=1, it can be determined that the Graph LIO supports 16-color mode.
Related DIP SW 1-8
Explanation o A work area that mainly indicates the functions and status related to graphics.
Related
Memory 0000:054Ch (Hi-Res)
Type 8bit FLAGS
Name
Classification CRT BIOS
Undocumented
Target Hi-Res
Contents CRT status
bit 7,6: 00b (unused)
bit 5: CRT mode
1 = Non-interlace (horizontal scan frequency 50.02kHz, vertical sync frequency 79.09Hz)
0 = Interlace (horizontal scan frequency 32.86kHz, vertical sync frequency 60.05Hz)
* PC-98XA, XL, XL^2, and RL are always 0.
bit 4: 0 (unused)
bit 3: User-defined number of characters
1 = 188 characters (fixed)
bit 2-0: 000b (unused)
Explanation o Work area that indicates the CRT-related status.
Related INT 0Ah (External interrupt...VSYNC)
Memory 0000:054Ch (LT/HA)
Type 8bit FLAGS
Name
Classification CRT BIOS
Undocumented
Target PC-98LT/HA, DB-P1
Content CRT status
Bit 7-4: 0000b (unused)
Bit 3: User-defined number of characters
1 = 188 characters (fixed)
Bit 2-0: 000b (unused)
Explanation o Always shows a fixed value (08h).
Related
Memory 0000:054Dh (Normal)
Type 8bit FLAGS
Name PRXDUPD
Classification
Target Normal
Content Graphics mode
bit 7:
■PC-H98
Whether or not 256-color board (PC-H98-E02) is installed (Undocumented)
1 = Yes
0 = No
■PC-9821 (excluding Bp, Bs, Be, Bf, Ts, Ne3, and Nd2)
Graphics mode (Undocumented)
1 = Enhanced graphics
0 = Standard graphics
* Not used for PC-98GS
Related INT 18h - Function 30h
INT 18h - Function 4Dh
bit 6: Whether or not EGC (Enhanced Graphic Charger) is installed (Undocumented)
1 = Yes
0 = No
* EGC is equipped on machines with an i80286 CPU or higher, and on machines equipped with a V30HL or V33A.
* On the PC-9801NS/E/NC, the EGC cannot be used when resume is ON (this bit becomes 0). On the PC-9801NS/T/NL and later,
the EGC can be used even with resume ON.
* The PC-9801NV has an EGC in hardware, but is normally set up so that it cannot be used.
If you execute OUT EE8Eh,00h and set this bit to 1, the EGC will be usable only when resume is OFF.
Related I/O 04A0h
I/O EE8Eh (PC-9801NV)
bit 5: DIP SW 2-8 [Excluding the original PC-9801, E, F, M, U, VM2, and VF] (Undocumented)
1 = ON (5.0MHz)
0 = OFF (2.5MHz)
* Indicates the state of DIP SW 2-8 at startup. Specifies the GDC clock frequency when the graphics resolution is 640x400.
This bit simply copies the state of the DIP-SW at startup, so it does not indicate the current GDC clock frequency.
Related 0000:054Dh bit 2
DIP SW 2-8
bit 4: Always flashless drawing flag (Undocumented)
1 = Models with always flashless drawing
0 = Models that do not always flashless drawing
* For models with this bit set to 1, flashless drawing is always performed regardless of INT 18h - Function 4Ah (drawing mode setting).
* Models with this bit set to 0 are the original PC-9801, E, F, M, U, VM2, and VF. For other models, it is set to 1.
Related INT 18h - Function 4Ah
bit 3: Flash drawing flag (Undocumented)
1 = Flash drawing
0 = Flashless drawing
* Setting value of INT 18h - Function 4Ah (drawing mode setting). 0000:054Dh
On models with bit 4=0, if flash drawing is set, flickering will occur on the screen when drawing with GDC.
* When 0000:054Ch bit 0=1, it is always set to 1 after executing INT 18h - Function 30h, 42h, etc., but the reason is unknown.
* On the PC-H98, it always shows 1, but the meaning is unknown.
Related INT 18h - Function 4Ah
bit 2: GDC clock (Undocumented)
1 = 5.0MHz
0 = 2.5MHz
* Shows the current GDC clock frequency.
* The GDC clock is set according to the conditions as shown in the table below.
-----------+----------------+---------------+-------------+--------------------------+------
Graphics | Horizontal scan| Vertical sync | Graphics | GDC clock | Notes
Resolution | Frequency | Frequency | Mode | (Bit values in brackets) |
-----------+----------------+---------------+-------------+--------------------------+------
640x200 | 15.98kHz | 61.47Hz | Standard | Fixed at 2.5MHz(0) | *1
640x200 | 24.83kHz | 56.42Hz | Standard | Fixed at 2.5MHz(0) | *2
640x400 | ↑ | ↑ | Standard | Follows 0000:054Dh bit 5 | *2
640x400 | ↑ | ↑ | Extended | Follows 0000:054Dh bit 5 | *2
640x200 | 31.47kHz | 70.10Hz | Standard | Fixed at 2.5MHz(0) | *3
640x400 | ↑ | ↑ | Standard | Follows 0000:054Dh bit 5 | *3
640x400 | ↑ | ↑ | Extended | Follows 0000:054Dh bit 5 | *3
640x480 | 31.47kHz | 59.94Hz | Extended | Fixed at 5.0MHz(1) | *4
640x400 | 15.73kHz | 59.94Hz | GS Extended | Fixed at 5.0MHz(1) | *5
640x480 | ↑ | ↑ | GS Extended | Fixed at 5.0MHz(1) | *5
-----------+----------------+---------------+-------------+--------------------------+------
*1: Models with digital RGB output, DIP CRT signal when SW 1-1 is turned OFF.
Setting when connecting a PC-8001 display.
*2: Most standard CRT signal in normal mode.
*3: CRT signal in normal mode when [GRPH]+[2]+[RESET] is set on PC-9821 (except original/Ne/Np/Ce/Ts),
PC-9801BA2/BS2/BX2/BA3/BX3/BX4, and when an N5926-01/02 type display is connected to a PC-H98 and
25 lines of space are not displayed.
*4: CRT signal when displaying 640x480 on PC-9821 (except Bp/Bs/Be/Bf/Ts/Ne3/Nd2), PC-H98 (normal), and PC-98GS (non-video mode).
*5: CRT signal when set to video mode on PC-98GS.
Related INT 18h - Function 30h,31h
bit 1,0: GDC dot operation mode setting status
11b = SET
10b = CLEAR
01b = COMPLEMENT
00b = REPLACE
Explanation o Work area showing graphics related functions and status.
o PC-98LT-HA, DB-P1 do not use this address.
Related
Memory 0000:054Dh (Hi-Res)
Type 8bit FLAGS
Name
Classification Undocumented
Target Hi-Res
Contents
bit 7: Presence or absence of 256-color board (PC-H98-E02) [PC-H98]
1 = Yes
0 = No
bit 6: EGC (Enhanced Graphic Charger)
1 = Yes
0 = No
* EGC is supported in Hi-Res mode except for PC-98XA.
Related I/O 04A0h
bit 5: 0 (unused)
bit 4: Always indicates 1 in Hi-Res mode of PC-H98 and Hi-Res mode of 98 Hi-Res board (PC-9821A-E02). Meaning unknown.
bit 3: Always indicates 1 in the high-resolution mode of the PC-H98 and the high-resolution mode of the 98 high-resolution board (PC-9821A-E02).
The meaning is unknown.
bit 2-0: 000b (unused)
Explanation o Work area indicating graphics-related functions.
Related
Memory 0000:054E-054Fh
Type 2 BYTES
Name PRXGLS
Category GRAPH BIOS
Target Normal
Contents Line type data to be set in GDC
Explanation o Area to store line type data (PTN) set by GDC's TEXTW command. Used by graphic BIOS and graph LIO.
o Shares area with the first 2 bytes of 0000:054Eh (PRXGCPTN).
Related
Memory 0000:054E-0555h
Type 8 BYTES
Name PRXGCPTN
Category GRAPH BIOS
Target Normal
Contents Dot configuration data to be set in GDC
Explanation o Area to store dot configuration data (TEXT1-8) set by GDC's TEXTW command. Used by graphic BIOS and graph LIO.
o Shares area with 0000:054Eh (PRXGLS).
Related
Memory 0000:0556-0559h
Type DWORD
Name RS_OFST_ADR,RS_SEG_ADR (Normal)
RS_CH0_OFST,RS_CH0_SEG (Hi-Res)
Classification RS-232C
Target Normal, Hi-Res, PC-98LT/HA
Contents RS-232C CH0 receive buffer address
Explanation o Holds the receive buffer address for RS-232C CH0 (built-in RS-232C). Used by RS-232C BIOS (INT 19h) and RSDRV.SYS.
Related 0000:055Bh
0000:05C1h
0000:05F0h
0000:05F4h
INT 19h - Function 00h (BIOS)
INT 19h - Function 00h (RSDRV)
Memory 0000:055Ah
Type 8bit FLAGS
Name PR_SIFT
Category PRINTER BIOS
Target PC-9801 first generation, E, F, M
Contents Shift state of ODA printer
bit 7-3: Unused
bit 2: Interrupt from ODA printer only
1 = Yes
0 = No
bit 1: Shift state
1 = State confirmed
0 = State uncertain
bit 0: Shift state
1 = SO state
0 = SI state
Explanation o Work area used when implementing PC-9801-05 (ODA printer interface).
Related
Memory 0000:055Bh
Type 8bit FLAGS
Name RS_S_FLAG
Classification RS-232C BIOS
Target Normal, High Resolution, PC-98LT/HA
Contents RS-232C receive data shift status
bit 7: CH 0 SI/SO conversion status
bit 6: CH 1 SI/SO conversion status
bit 5: CH 2 SI/SO conversion status
1 = Yes
0 = No (initial state)
bit 4: CH 0 SI/SO shift status
bit 3: CH 1 SI/SO shift status
bit 2: CH 2 SI/SO shift status
bit 1,0: 00b (unused)
1 = SO
0 = SI (initial state)
Explanation o Holds the status of RS-232C SI/SO conversion and the receive data shift status.
Used by RS-232C BIOS (INT 19h, INT D4h, INT D5h) and RSDRV.SYS.
Related 0000:0556h
0000:05C1h
0000:05F0h
0000:05F4h
Memory 0000:055C-055Dh
Type 16bit
Name DISK_EQUIP
Classification DISK BIOS
Target All models
Content Disk connection status
------------+------------------+------------------
Address/bit | Device type |Notes
------------+------------------+------------------
055Ch bit 7 | 320KB FDD UNIT#3 | (DA/UA=53h) *1
bit 6 | 320KB FDD UNIT#2 | (DA/UA=52h) *1
bit 5 | 320KB FDD UNIT#1 | (DA/UA=51h) *1
bit 4 | 320KB FDD UNIT#0 | (DA/UA=50h) *1
bit 3 | 1MB FDD UNIT#3 | (DA/UA=93h,13h)
bit 2 | 1MB FDD UNIT#2 | (DA/UA=92h,12h)
bit 1 | 1MB FDD UNIT#1 | (DA/UA=91h,11h)
bit 0 | 1MB FDD UNIT#0 | (DA/UA=90h,10h)
055Dh bit 7 | 640KB FDD UNIT#3 | (DA/UA=73h,F3h)
bit 6 | 640KB FDD UNIT#2 | (DA/UA=72h,F2h)
bit 5 | 640KB FDD UNIT#1 | (DA/UA=71h,F1h)
bit 4 | 640KB FDD UNIT#0 | (DA/UA=70h,F0h)
bit 3 | SASI HDD UNIT#3 | (DA/UA=83h,03h) *2
bit 2 | SASI HDD UNIT#2 | (DA/UA=82h,02h) *3
bit 1 | SASI HDD UNIT#1 | (DA/UA=81h,01h) *4
bit 0 | SASI HDD UNIT#0 | (DA/UA=80h,00h) *5
------------+------------------+------------------
1 = Connected
0 = Not connected
*1: Only PC-9801 original, E, F, and M are supported
*2: Same for external SASI drive or 4th IDE HDD connected to PC-H98/70-E01/E03
*3: Same for PC-H98/70-E01/E03 (PC-H98 built-in SASI), PC-H98/70-E02 (PC-H98 built-in ESDI) or 3rd IDE HDD
*4: Same for 2nd IDE HDD
*5: Same for 1st IDE HDD
Explanation o The connection status of the disk device is set when the DISK BIOS INITIALIZE command is executed.
o In the case of a dual-use FDD interface or a 1.44MB dual-use interface, it is recognized as a drive in the set I/F mode.
In other words, in the 1MB I/F mode, none of 0000:055Dh bits 7-4 can be 1. If they were 1, it means that a 640KB FD I/F board
is installed and a 640KB FD is connected to it. Similarly, in the 640KB I/F mode, none of 0000:055Ch bits 3-0 can be 1. If
they were 1, it means that a 1MB FD I/F board is installed and a 1MB FD is connected to it.
o It is not possible to determine from the work area whether the FDD is a dual-use drive or a 3-mode drive. It can be
distinguished from the return value of INT 1Bh - Function 84h (FD), C4h (FD).
On the PC-9821Np and Ns, even if there is no internal FDD installed in the 98NOTE bay, this work area will show that a
single 1MB dedicated FDD is connected (which is why an MS-DOS drive is also created).
The status of the FDD installed in the 98NOTE bay will not be detected even if it is inserted or removed while the power is on
(the FDD display on the status indicator will not change. Even if you insert an FDD after booting with the FDD removed, you will
not be able to access the FD). Furthermore, such operations are prohibited. It is unclear what the significance is of the 1MB
dedicated FDD always appearing to be connected.
Related 0000:0482h
0000:0488h
0000:0494h
0000:0560h
0000:05AEh
INT 1Bh - Function 04h(FD)
INT 1Bh - Function 84h(FD)
INT 1Bh - Function C4h(FD)
Memory 0000:055E-055Fh
Type 16bit
Name DISK_INT
Classification DISK BIOS
Target All models
Contents Interrupt status from disk device
--------------+-----------------
Address/bit | Device type
--------------+-----------------
055Eh bit 7-4 | Unused
bit 3 | 1MB FDD UNIT#3
bit 2 | 1MB FDD UNIT#2
bit 1 | 1MB FDD UNIT#1
bit 0 | 1MB FDD UNIT#0
055Fh bit 7 | 640KB FDD UNIT#3
bit 6 | 640KB FDD UNIT#2
bit 5 | 640KB FDD UNIT#1
bit 4 | 640KB FDD UNIT#0
bit 3-1 | Unused
bit 0 | SASI/ESDI/IDE HDD
--------------+-----------------
1 = An interrupt occurred from the corresponding device
0 = No interrupt
Explanation o Indicates the interrupt status from the disk device.
Related
Memory 0000:0560h
Type BYTE
Name DISK_TYPE
Classification DISK BIOS
Target PC-9801 original/E/F/M
Contents 320KB FD type
FFh = Single-sided device
EFh = Double-sided device
00h = Not connected
Explanation o Indicates the connection status and device type of the 320KB FD drive.
Related 0000:055Ch
Memory 0000:0561h
Type 8bit FLAGS
Name DISK_MODE
Classification DISK BIOS
Target PC-9801 original/E/F/M
Contents 320KB FDD operating mode
bit 7-4: Unused
bit 3: 320KB FDD UNIT#3
bit 2: 320KB FDD UNIT#2
bit 1: 320KB FDD UNIT#1
bit 0: 320KB FDD UNIT#0
1 = Double-sided
0 = Single-sided
Explanation o Indicates the operating mode of the 320KB FDD.
Related 0000:0560h
Memory 0000:0562-0563h
Type WORD
Name DISK_TIME
Classification DISK BIOS
Target PC-9801 original/E/F/M
Content 320KB FD timeout time (unit: ms)
Explanation o Performs timeout processing when booting from a 320KB FD.
When set to 0, it will unconditionally wait until completion. When power is ON/RESET, it is set to approximately 35 seconds.
Related 0000:0560h
Memory 0000:0564-0583h
Type 32 BYTES
Name DISK_RESULT
Classification DISK BIOS
Target 1MB dedicated BIOS, dual-use BIOS - 1MB I/F mode
Contents 1MB FD I/F FDC result status
-----------+---------------
Address | Contents
-----------+---------------
0564-056Bh | 1MB FDD UNIT#0
056C-0573h | 1MB FDD UNIT#1
0574-057Bh | 1MB FDD UNIT#2
057C-0583h | 1MB FDD UNIT#3
-----------+---------------
----------+---------------------------------------------
Offset | Contents
----------+---------------------------------------------
+0 | ST0(Result status)
| bit 7: IC1(Interrupt Code 1)
| bit 6: IC0 (Interrupt Code 0)
| bit 5: SE (Seek End)
| bit 4: EC (Equipment check)
| bit 3: NR (Not Ready)
| bit 2: HD (Head Address)
| bit 1: US1 (Unit Select 1)
| bit 0: US0 (Unit Select 0)
----------+---------------------------------------------
+1 | ST1 (Result Status) or
| PCN (Present Cylinder Number) * 1
| bit 7: EN (End of Cylinder)
| bit 6: 0
| bit 5: DE (Data Error)
| bit 4: OR (Overrun)
| bit 3: 0
| bit 2: ND (No Data)
| bit 1: NW (Not Writable)
| bit 0: MA (Missing Address Mark)
----------+---------------------------------------------
+2 | ST2 (Result Status)
| bit 7: 0
| bit 6: CM (Control Mark)
| bit 5: DD (Data Error in Data Field)
| bit 4: NC (No Cylinder)
| bit 3: SH (Scan Equal Hit)
| bit 2: SN (Scan Not Satisfied)
| bit 1: BC (Bad Cylinder)
| bit 0: MD (Missing Address Mark in Data Field)
----------+---------------------------------------------
+3 | C (Cylinder number)
+4 | H (Head number)
+5 | R (Record number)
+6 | N (Data length)
+7 | NCN (Current cylinder number)
----------+---------------------------------------------
*1: Used as PCN when bit 5 (SE) of ST0 = 1.
Explanation o Status information returned from FDC (μPD765A) when disk I/O is completed.
Only ST0 and PCN are notified by SEEK commands.
o In dual-use FD I/F, this work area is used even in 640KB access mode if the I/F mode is 1MB.
Related 0000:05D0h
0000:05D8h
I/O 0090h
Memory 0000:0584h
Type BYTE
Name DISK_BOOT
Classification DISK BIOS
Target All models
Contents DA/UA of the disk device that the OS booted from
-------+---------------------------------------------------------
DA/UA | Device type
-------+---------------------------------------------------------
10-13h | FDD (640KB media) connected to dual-use FD I/F (1MB I/F mode)
30-33h | FDD (1.44MB media) connected to dual-use FD I/F (1MB I/F mode)
50-53h | FDD connected to 320KB FD I/F
68-6Bh | Virtual drive connected to BRANCH 4670 I/F
70-73h | FDD connected to 640KB FD I/F, dual-use FD I/F (640KB I/F mode)
| (640KB media)
80-83h | SASI, ESDI, IDE HDD
90-93h | 1MB FD I/F, FDD connected to dual-purpose FD I/F (1MB I/F mode)
| (1MB media)
A0-A6h | HDD connected to SCSI I/F, 3.5"MO, 5"MO, CD-ROM
D0h | ROM drive
D1h | PCMCIA memory card drive
F0-F3h | FDD (1MB media) connected to dual-purpose FD I/F (640KB I/F mode)
-------+---------------------------------------------------------
Explanation o Indicates the DA/UA of the disk device from which the OS was booted.
Related FD80:27E8h (normal)
FD80:27ECh (normal)
F800:7FECh (high-resolution)
Memory 0000:0585h
Type 8bit FLAGS
Name DISK_STATUS
Classification DISK BIOS
Target SASI, ESDI
Contents Completion Status of HDC (Hard Disk Controller)
bit 7,6: 00b
bit 5: LUN (Logical Unit Number)
1 = HDD#1
0 = HDD#0
bit 4-2: Undefined
bit 1: Error
1 = Error occurred
0 = No error
bit 0: Parity error
1 = Error occurred
0 = No error
Explanation o When disk I/O is completed, the Completion Status of HDC (I/O 0080h) is stored.
o IDE BIOS does not use this address.
Related I/O 0080h
Memory 0000:0586-0589h
Type 4 BYTES
Name DISK_SENSE
Classification DISK BIOS
Target SASI, ESDI
Contents SASI/ESDI BIOS work area
--------+------------------------------------------
Address | Contents
--------+------------------------------------------
0586h | Sense byte
0587h | Logical address bits 21-16 (top 2 bits are 0)
0588h | Logical address bits 15-8
0589h | Logical address bits 7-0
--------+------------------------------------------
Explanation o IDE BIOS does not use this address.
Related
Memory 0000:058A-058Bh
Type WORD
Name CA_TIM_CNT
Category TIMER BIOS
Target All models
Contents Interval timer counter (unit: 10ms)
Explanation o Interval timer counter for single event timer. For details, see the explanation for INT 1Ch - Function 02h.
u In DB-P1, the value is set in 50ms units.
Related INT 1Ch - Function 02h
Memory 0000:058C-058Dh
Type WORD
Name
Category DISK BIOS
Undocumented
Target PC-9821Xa10, Xa9, Xa7, Xa12
Contents Motor stop time counter for the third IDE hard disk (unit: 100ms)
Explanation o When "Set internal fixed disk control", this address is used to count the motor stop time.
When this value is decremented to 0000h, the HDD spindle motor stops.
o When "Built-in fixed disk control - not set" is selected, it is always 0000h.
o The INT 17h handler decrements it.
Related 0000:04FEh
0000:059Ah
0000:05B1h
0000:058Eh
INT 17h (External interrupt... calendar clock interrupt)
INT 1Bh - Function D0h (IDE)
INT 1Bh - Function E0h (IDE)
INT 1Bh - Function F0h (IDE)
Memory 0000:058E-058Fh
Type WORD
Name
Classification DISK BIOS
Undocumented
Target PC-9821Xa10, Xa9, Xa7, Xa12
Contents Motor stop time counter for the 4th IDE hard disk (unit: 100ms)
Explanation o When "Built-in fixed disk control set", this address is used to
count the motor stop time. When this value is decremented to 0000h, the HDD spindle motor stops.
o When "Built-in fixed disk control not set", it is always 0000h.
o The INT 17h handler decrements.
Related 0000:04FEh
0000:059Ah
0000:05B1h
0000:058Ch
INT 17h (External interrupt...Calendar clock interrupt)
INT 1Bh - Function D0h (IDE)
INT 1Bh - Function E0h (IDE)
INT 1Bh - Function F0h (IDE)
Memory 0000:058E-05BFh
Type 50 BYTES
Name PRXGDCQ
Classification GRAPHIC LIO
Target PC-9801 first generation
Contents Area for high-speed control of PAINT processing
Explanation o Used as a work area for Graphic LIO.
o Not used on PC-9801E/F/M and later models.
Related
Memory 0000:058E-058Fh
Type 2 BYTES
Name
Classification DISK BIOS
Undocumented
Target PC-H98/70-E01, E02, E03
Contents Extended DISK BIOS ROM address related
Explanation o Details unknown.
0000:058Eh stores the memory area start address (bits 19-16 of the CPU address) obtained by INT 1Fh - Function C4h (DL=04h).
0000:058Fh stores the actual (copied from the CS register) extended DISK BIOS address (bits 19-16 of the CPU address).
Related
Memory 0000:0590h
Type 8bit FLAGS
Name ADR_MOD
Category DISK BIOS
Target PC-H98
Contents H98 DISK BIOS mode
bit 7: Current SASI (ESDI, IDE) BIOS access mode
1 = Indirect mode access
0 = Direct mode access
bit 6: SASI (ESDI, IDE) BIOS indirect mode support
1 = Supported
0 = Not supported
* When PC-H98/70-E01, E02, E03 or PC-9801-27 is implemented, it is not
supported in normal mode and supported in high-resolution mode.
bit 5: Current SCSI BIOS access mode
1 = Indirect mode access
0 = Direct mode access
bit 4: SCSI BIOS indirect mode support
1 = Supported
0 = Not supported
* Supported by PC-H98S/8-E02, PC-H98-B03 and B12.
Not supported by PC-9801-55 original, 55L, 55U, 92 and 100.
bit 3: Current FD BIOS access mode
1 = Indirect mode access
0 = Direct mode access
bit 2: FD BIOS indirect mode support
1 = Supported
0 = Not supported
* No models support indirect mode with FD BIOS.
bit 1: ESDI HD #1 mode (Undocumented)
bit 0: ESDI HD #0 mode (Undocumented)
Explanation o Bits 7-2 store information about the indirect mode of the PC-H98.
The PC-H98 supports an indirect mode that allows transfers to areas over 1MB
in the DISK BIOS. Bits 7-2 indicate which DISK BIOS supports indirect mode and
which mode is currently set.
o In direct mode, the transfer address is specified directly by ES:BP, but in
indirect mode, the transfer address is specified indirectly by ES:BP. At this
time, the transfer address is written in memory as a 32-bit linear address.
ES:BP specifies the address of the memory where the 32-bit linear address is written.
Once the BIOS is executed in indirect mode, it always returns to direct mode.
o Bits 1 and 0 are used when the PC-H98 built-in ESDI HDD (PC-H98/70-E01, E02,
E03, PC-H98S/8-E01) is in normal mode. Details unknown. See INT 1Bh - Function 0Eh
(SASI/ESDI/IDE).
Related 0000:0590h bit 1
0000:05ECh
INT 1Bh - Function 0Eh (SASI/ESDI/IDE)
Memory 0000:0591h
Type 8bit FLAGS
Name
Classification DMA BIOS
Undocumented
Target PC-H98
Content DMA channel usage
bit 7: DMA CH7
bit 6: DMA CH6
bit 5: DMA CH5
bit 4: DMA CH4
bit 3: DMA CH3
bit 2: DMA CH2
bit 1: DMA CH1
bit 0: DMA CH0
1 = In use
0 = Not in use
Explanation o Flag indicating DMA channel usage.
o When DMA BIOS INT 1Fh - Function D2h (channel allocation) is executed, the bit corresponding to the specified channel becomes 1.
When INT 1Fh - Function D7h (channel release) is executed, the bit corresponding to the specified channel becomes 0.
Related INT 1Fh - Function D2h
INT 1Fh - Function D7h
Memory 0000:0592-0593h
Type 2 BYTES
Name
Classification Undocumented
Target PC-H98
Content Used by NMI handler
Explanation o Details unknown. Used by NMI handler for both normal and high resolution.
Related INT 02h (CPU exception)
Memory 0000:0594-0595h
Type WORD
Name
Classification MEMORY
Undocumented
Target Machines capable of installing memory over 16MB
Content Usable protected mode memory capacity over 16MB (unit: MB)
Explanation o Indicates the amount of usable protected mode memory located at addresses 1000000h (16M) and above. Valid for PC-H98, PC-9821Af and later
PC-9821 series, PC-9801BA2, BS2, BX2, BA3, BX3, BX4.
u Also serves as a work space for managing resources for HIMEM.SYS. When HIMEM.SYS compatible with memory over 16MB is installed, 0000h is written
to this address. After HIMEM.SYS is installed, it will no longer indicate the actual memory capacity.
Some versions of HIMEM.SYS (such as the version included with MS-DOS 5.0A-H) do not support memory over 16MB, but set this address to 0000h when installed.
o The amount of memory located at addresses 00000-9FFFFh (normal mode) / 00000-BFFFFh (high-resolution mode) is stored in 0000:0501h bits 2-0.
The amount of memory located at addresses 100000h (1MB)-FFFFFFh (16MB-1) is stored in 0000:0401h.
Related 0000:0401h
0000:0501h bits 2-0
INT DC - Function 81h
INT DC - Function 82h
Memory 0000:0596h
Type 8bit FLAGS
Name
Classification Undocumented
Target PC-H98
Contents Bit 7-4: Unused
Bit 3: CPU cache
1 = OFF
0 = ON
Bit 2: Expansion board implementation status with product code = 09h and function ID (4) = 80h
1 = Yes
0 = No
* 640KB Appears to be related to the FD I/F. Details such as the board's product name are unknown.
Related INT 1Fh - Function C0h
INT 1Fh - Function C2h
bit 1: Setting value of INT 1Fh - Function DFh
1 = After execution with BH=00h
0 = After execution with anything other than BH=00h
Related INT 1Fh - Function DFh
I/O 0431h
bit 0: Value output to I/O 00F0h when CPU is shut down
1 = Execute OUT 00F0h,01h
0 = Execute OUT 00F0h,00h
Explanation o Details of the function of bits 2,1 are unknown.
u In the first edition of UNDOCUMENTED 9801/9821 Vol.1, INT 1Fh - Function DFh
is described as "Power OFF prohibition/permission setting", but this is
incorrect. Its actual function is unknown.
o Bits 3,0 are as follows depending on the "CPU speed" setting in the system setup menu.
----------+-----------------
CPU speed | bit 3,0 status
----------+-----------------
HIGH | bit 3=0, bit 0=0
MIDDLE | bit 3=0, bit 0=1
LOW | bit 3=1, bit 0=1
----------+-----------------
Related
Memory 0000:0596h
Type 8bit FLAGS
Name Classification Undocumented Target PC-9821,
PC-9801FA･FS･FX･US･BA･BX･BA2･BS2･BX2･BA3･BX3･BX4･ NA･NS/R･NX/C･NS/A･NL/R
Contents CPU speed
bit 7~4: unused
bit 3: CPU cache
1=OFF
0=ON
bit 2,1: 00b (unused)
bit 0: CPU speed
1=low speed
0=fast
Table Bit 3,0 values by model and CPU speed
-----------------+------+--------+------+
Model name | HIGH | MIDDLE | LOW |
-----------------+------+--------+------+
PC-9801FA | 0,0 | 1,1 | 1,1 |
PC-9801FS | 0,0 | 0,0 | 0,1 |
PC-9801FX | 0,0 | 0,0 | 0,1 |
PC-9801US | 0,0 | None | 0,1 |
PC-9821 original | 0,0 | None | 0,1 |
PC-9821Af | 0,0 | 0,0 | 1,1 |
PC-9821Bf | 0,0 | 0,0 | 1,1 |
PC-9801NS/R | 0,0 | None | 1,1 |
PC-9801NL/R | 0,0 | None | 0,1 |
PC-9801NS/A | 0,0 | 1,1 | 1,1 |
PC-9821Np | 0,0 | ? | ? |
Other*1 | 0,0 | 0,1 | 1,1 |
-----------------+------+--------+------+
*1: PC-9821Ap･As･Ae･Ap2･As2･Ap2･As2･An･Bp･Bs･Be･Ce･Cs2･Ce2･Ne･Ts,
PC-9801BA･BX･BA2･BS2･BX2･BA3 ･BX3･BX4･NA･NX/C
Explanation o Changes depending on the CPU speed setting.
Bit 3 is set to 1 when the CPU cache is OFF on machines with i486 or Pentium.
Related CPU speed
Memory 0000:0597h
Type 8bit FLAGS
Name
Category CRT BIOS
Undocumented
Target PC-98GS, PC-9821, PC-9801BA2･BS2･BX2･BA3･BX3･BX4
bit 7: INT 18h - Function 30h,31h support
1 = Yes
0 = No
* 1 is for PC-98GS (when running 386SX), PC-9821,
PC-9801BA2･BS2･BX2･BA3･BX3･BX4･NL/A. For other models and PC-98GS V30, the value is 0.
* On PC-98GS, PC-9821, PC-9801BA2, BS2, BX2, BA3, BX3 and BX4, setting this bit to 0 will disable INT 18h - Function 30h, 31h.
* The PC-9821Ts, Ne2 and Nd are exceptions; this bit indicates 1, but INT 18h - Function 30h, 31h are not supported.
* If AVGDRV.SYS is installed in an environment where this value is 0, the message "AV function is disabled" will be displayed.
Related INT 1Fh - Function 00h (PC-98GS)
INT 1Fh - Function 01h (PC-98GS)
bit 6-3: 0000b (unused)
bit 2: Support for extended graphics mode and GS extended graphics mode
1 = Yes
0 = No
* 1 is for PC-9821 original, Ap, As, Ae, Af, Ap2, As2, An, Ce, Cs2, Ce2, Ne, Np, and PC-98GS.
PC-9821Bp, Bs, Be, Bf, Ts, Ne2, Nd, and PC-9801BA2, BS2, BX2, BA3, BX3, and BX4 are 0.
bit 1,0: Graphics resolution
------+---------------------+------------------------------
Value | Graphics resolution | Number of simultaneous colors
------+---------------------+------------------------------
00b | 640x200(UPPER) | 2/8/16 colors
01b | 640x200(LOWER) | 2/8/16 colors
10b | 640x400 | 2/8/16/256 colors
11b | 640x480 *1 | 256 colors
------+---------------------+------------------------------
*1 PC-9821Bp, Bs, Be, Bf, Ts, Ne2, and Nd do not support extended graphics mode and will not enter this state.
Explanation o The graphics resolution indicated by bit 1,0 is reflected correctly even when the resolution is changed using INT 18h - Function 42h.
Therefore, even on PC-9821Ts, Ne2, and Nd, which do not support INT 18h - Function 30h, 31h, these two bits reflect the resolution status.
Related INT 18h - Function 30h
INT 18h - Function 31h
INT 18h - Function 42h
Memory 0000:0598-0599h
Type WORD
Name
Classification DISK BIOS
Undocumented
Target 98NOTE with built-in HDD,
PC-9821Ap2･As2･An･Bp･Bs･Be･Bf･Cs2･Ce2･Ts･Xa･Xn･Xp･Xs･Xe,
PC-9801BA2･BS2･BX2･BA3･BX3･BX4
Contents Motor stop time counter for the first IDE hard disk (unit: 100ms)
Explanation o When "Built-in fixed disk control set", this address is used to
count the motor stop time. When this value is decremented to 0000h, the HDD
spindle motor stops.
o When "Built-in fixed disk control not set", it is always 0000h.
o In 98NOTE, the system timer (INT 0Eh or INT 17h) handler decrements this value. On desktops, the INT 17h handler decrements it.
Related 0000:04FEh
0000:059Ah
0000:05B1h
0000:058Ch
0000:058Eh
INT 0Eh (External interrupt...98NOTE)
INT 17h (External interrupt...98NOTE)
INT 17h (External interrupt...IDE)
INT 1Bh - Function D0h (IDE)
INT 1Bh - Function E0h (IDE)
INT 1Bh - Function F0h (IDE)
Memory 0000:059A-059Bh
Type WORD
Name
Classification DISK BIOS
Undocumented
Target HDD built-in 98NOTE,
PC-9821Ap2･As2･An･Bp･Bs･Be･Bf･Cs2･Ce2･Ts･Xa･Xn･Xp･Xs･Xe,
PC-9801BA2･BS2･BX2･BA3･BX3･BX4
Contents Initial value of motor stop time for IDE hard disk (unit: 100ms)
Explanation o When "Built-in fixed disk control not set" is selected, the value is 0000h.
Related 0000:0598h
0000:05B1h
Memory 0000:059C-059Dh (NOTE)
Type 2 BYTES
Name
Classification Undocumented
Target 98NOTE (excluding PC-9801N/NS)
Contents ■PC-9801NV/NS/E/NC/NS/T/NL/NS/L/NA
0000:059Ch (BYTE): NOTE RAM bank I/O 0E8Eh (BYTE) storage area
0000:059Dh (BYTE): NOTE RAM bank I/O 1E8Eh (BYTE) storage area
■PC-9801NS/R/P/NX/C/NL/R/NS/A, PC-9821Ne/Np/Ns/Ne2/Nd/Es
0000:059Ch (WORD): NOTE RAM bank I/O 0E8Eh (WORD) storage area
Explanation o NOTE When switching RAM banks, the contents of the bank switching I/O port are saved.
Related 0000:059Eh
I/O 0E8Eh
I/O 1E8Eh
Memory 0000:059Eh (NOTE)
Type 8bit FLAGS
Name
Classification Undocumented
Target 98NOTE (excluding PC-9801N, NS, and NV)
Content NOTE special function activation instruction flag
bit 7: Power OFF request
1 = Power OFF
0 = No Operation
bit 6: Power OFF request mask
1 = Power OFF prohibited
0 = Power OFF permitted
bit 5-4: Unknown
bit 3: Note menu request
1 = [CTRL]+[GRPH]+[HELP] pressed
0 = No Operation
bit 2: Note menu internal flag
1 = Note menu currently being executed
0 = Note menu not being executed
bit 0: Note menu request mask
1 = Note menu request ignored
0 = Note menu request not ignored
Explanation o Requests the calling of the Note menu, etc.
Related INT 0Eh (External interrupt...98NOTE)
INT 17h (External interrupt...98NOTE)
INT 1Fh - Function 9A1Dh
INT 1Fh - Function 9A1Eh
Memory 0000:059Fh
Type BYTE
Name
Classification Undocumented
Target PC-9801NS/T･NS/R･P･NX/C･NL/R･NS/A, PC-9821Ne･Np･Ns･Ne2･Nd･Es
Contents ■PC-9801NS/T
NOTE I/O for RAM bank 0E8Fh port storage area
■PC-9801NS/R･P･NX/C･NL/R･NS/A, PC-9821Ne･Np･Ns･Ne2･Nd･Es
NOTE I/O for RAM bank 1E8Eh port storage area
Explanation o NOTE When switching the RAM bank, the contents of the bank switching I/O port are saved.
Related 0000:059Ch
I/O 0E8Fh[PC-9801NS/T]
I/O 1E8Eh [other than PC-9801NS/T]
Memory 0000:059C-059Dh (HA)
Type WORD
Name CARD_SIZE
Classification PCMCIA memory card BIOS
Target PC-98HA
Contents Size of PCMCIA memory card
bit 15-8: Reserved
bit 7-3: Mantissa - 1 (Y)
bit 2-0: Exponent (X)
Capacity = (Y+1) * (4^X / 2) (unit: KB)
Explanation u There is no area showing the memory card capacity in the system
common area of PCMCIA slot-equipped machines other than PC-98HA.
To get the memory card capacity, execute INT 1Fh - Function B6h.
Related 0000:059Eh
INT 1Fh - Function B6h
Table [Table showing the relationship between X, Y and capacity] (unit: byte)
-----+------+-------+-------+-------+-------+-------+-------
Y＼X| 0| 1| 2| 3| 4| 5| 6
-----+------+-------+-------+-------+-------+-------+-------
00h | 0.5K| 2.0K| 8.0K| 32.0K| 128.0K| 0.5M| 2.0M
01h | 1.0K| 4.0K| 16.0K| 64.0K| 256.0K| 1.0M| 4.0M
02h | 1.5K| 6.0K| 24.0K| 96.0K| 384.0K| 1.5M| 6.0M
03h | 2.0K| 8.0K| 32.0K| 128.0K| 512.0K| 2.0M| 8.0M
04h | 2.5K| 10.0K| 40.0K| 160.0K| 640.0K| 2.5M| 10.0M
05h | 3.0K| 12.0K| 48.0K| 192.0K| 768.0K| 3.0M| 12.0M
06h | 3.5K| 14.0K| 56.0K| 224.0K| 896.0K| 3.5M| 14.0M
07h | 4.0K| 16.0K| 64.0K| 256.0K|1024.0K| 4.0M| 16.0M
08h | 4.5K| 18.0K| 72.0K| 288.0K|1152.0K| 4.5M| 18.0M
09h | 5.0K| 20.0K| 80.0K| 320.0K|1280.0K| 5.0M| 20.0M
0Ah | 5.5K| 22.0K| 88.0K| 352.0K|1408.0K| 5.5M| 22.0M
0Bh | 6.0K| 24.0K| 96.0K| 384.0K|1536.0K| 6.0M| 24.0M
0Ch | 6.5K| 26.0K| 104.0K| 416.0K|1664.0K| 6.5M| 26.0M
0Dh | 7.0K| 28.0K| 112.0K| 448.0K|1792.0K| 7.0M| 28.0M
0Eh | 7.5K| 30.0K| 120.0K| 480.0K|1920.0K| 7.5M| 30.0M
0Fh | 8.0K| 32.0K| 128.0K| 512.0K|2048.0K| 8.0M| 32.0M
10h | 8.5K| 34.0K| 136.0K| 544.0K|2176.0K| 8.5M| 34.0M
11h | 9.0K| 36.0K| 144.0K| 576.0K|2304.0K| 9.0M| 36.0M
12h | 9.5K| 38.0K| 152.0K| 608.0K|2432.0K| 9.5M| 38.0M
13h | 10.0K| 40.0K| 160.0K| 640.0K|2560.0K| 10.0M| 40.0M
14h | 10.5K| 42.0K| 168.0K| 672.0K|2688.0K| 10.5M| 42.0M
15h | 11.0K| 44.0K| 176.0K| 704.0K|2816.0K| 11.0M| 44.0M
16h | 11.5K| 46.0K| 184.0K| 736.0K|2944.0K| 11.5M| 46.0M
17h | 12.0K| 48.0K| 192.0K| 768.0K|3072.0K| 12.0M| 48.0M
18h | 12.5K| 50.0K| 200.0K| 800.0K|3200.0K| 12.5M| 50.0M
19h | 13.0K| 52.0K| 208.0K| 832.0K|3328.0K| 13.0M| 52.0M
1Ah | 13.5K| 54.0K| 216.0K| 864.0K|3456.0K| 13.5M| 54.0M
1Bh | 14.0K| 56.0K| 224.0K| 896.0K|3584.0K| 14.0M| 56.0M
1Ch | 14.5K| 58.0K| 232.0K| 928.0K|3712.0K| 14.5M| 58.0M
1Dh | 15.0K| 60.0K| 240.0K| 960.0K|3840.0K| 15.0M| 60.0M
1Eh | 15.5K| 62.0K| 248.0K| 992.0K|3968.0K| 15.5M| 62.0M
1Fh | 16.0K| 64.0K| 256.0K|1024.0K|4096.0K| 16.0M| 64.0M
-----+------+-------+-------+-------+-------+-------+-------
* X=7 is reserved
Memory 0000:059Eh(HA)
Type 8bit FLAGS
Name CARD_STATUS
Category PCMCIA memory card BIOS
Target PC-98HA
Contents PCMCIA memory card status
bit 7: Access status
1 = Accessing
0 = Not accessing
bit 6: Read/write
1 = Write
0 = Read
* Valid when bit 7=1
bit 5: Card valid/invalid
1 = Card invalid
0 = Card valid
* Unrecognized when bit 0,1=00b
bit 4: Card swap detection
1 = Swapped
0 = Not swapped
* Set to 1 when the slot cover is opened and closed.
* Can be used to detect card swap when creating device drivers, etc. In other words, the device driver is created
to set this bit to 0 when the PCMCIA memory card is accessed. If this bit remains 0 the next time it is accessed,
it means the card has not been swapped. If it is set to 1, you know that the card has been replaced.
bit 3: Card presence/absence
1 = Present
0 = Not present
* Set to 1 or 0 when the slot cover is opened or closed.
bit 2: Write protection
1 = Present
0 = Not present
* Valid when bit 3=1 (card present).
* Always 1 when bit 0=1 (EMS card).
* Always 1 for ROM cards.
bit 1: RAM/ROM card identification
1 = RAM/ROM card
0 = Other
* Valid when bit 5=0 (after card identification)
bit 0: EMS card identification
1 = EMS card
0 = Other
* Valid when bit 5=0 (after card identification)
Explanation o Indicates the status of the PCMCIA memory card.
u On PC-9801NL, PC card slot equipped machines, the same information is stored at 0000:05A6h.
Related 0000:059Ch
0000:05A6h
Memory 0000:059F-05AFh(HA)
Type 16 BYTES
Name
Classification Undocumented
Target PC-98HA, DB-P1
Contents ------------+-------------------------------------------------
Address | Contents
------------+-------------------------------------------------
059Fh(BYTE) | bit 7,5-0: Unknown
| bit 6: INT 1Fh - Becomes 1/0 when Function B0h,B1h is executed
05A0h(BYTE) | I/O Holds the value output to 1E8Eh
05A1h(BYTE) | I/O Holds the value output to 0E8Eh
05A2h(BYTE) | Unknown. PCMCIA related ■PC-98HA only
05A3h(BYTE) | Value to be output to I/O 8810h in INT 10-17h handler of PC-98HA.
| Copy of memory switch 13h. ■PC-98HA only
05A4h(BYTE) | Down counter for PCMCIA ■PC-98HA only
05A5h(BYTE) | Unknown
05A6h(BYTE) | Value to be output to I/O 0075 (1st time) ■PC-98HA only
05A7h(BYTE) | Value to be output to I/O 0075 (2nd time) ■PC-98HA only
05A8-05AFh | Unused
------------+-------------------------------------------------
Explanation o Details unknown
Related
Memory 0000:05A0h
Type 8bit FLAGS
Name
Classification Undocumented
Target 98NOTE (excluding PC-9801N and NS)
Contents Work area for LOW BATTERY warning sound
bit 7: Unused
bit 6: Warning beep sound on/off
1 = Sounding
0 = Not sounding
bit 5-0: Beep counter
Incremented by 1 every 0.1 seconds in the range of 0-63. Also, the sound is
turned on and off repeatedly at the timing shown in the following table.
Table |-Sound--|-Stop--|-Sound--|-Stop--------|
| On | Stop | On | Stop |
→0→1→2→3→4→5→6→…→63→↓
↑←―――――――――――――――――――
Explanation o Manages the sounding of the battery warning beep.
Related
Memory 0000:05A1-05A3h
Type 3 BYTES
Name
Classification Undocumented
Target PC-9801NV
Contents Waiting area for tone information when LOW BATTERY warning sound is sounded
------------+-------------------------------------------------
Address | Contents
------------+-------------------------------------------------
05A1h(BYTE) | Status data of counter #1 of μPD71054 (programmable timer counter)
| bit 7: OUTPUT
| bit 6: Null Count
| bit 5: RWM1
| bit 4: RWM0
| bit 3: CM2
| bit 2: CM1
| bit 1: CM0
| bit 0: BCD
05A2h(WORD) | Frequency division value of counter #1 of μPD71054
------------+---------------------------------------------------
Explanation o On the PC-9801NV, when sounding the LOW BATTERY warning sound, the hardware for sounding a normal beep is used. For this reason, when
sounding the warning sound, it is necessary to save and restore the current state of timer counter #1.
o 98NOTE other than the PC-9801NV has dedicated hardware for sounding the LOW BATTERY warning sound, so this process is not necessary.
Related I/O 0071h
Memory 0000:05A4h
Type 8bit FLAGS
Name
Classification Undocumented
Target PC-9801FA/FS/FX/US/BA/BX/BA2/BS2/BX2/BA3/BX3/BX4, PC-H98model105, PC-9821 (excluding 98NOTE), PC-9821A-E02 (high-resolution mode)
Contents FDD spindle motor status
bit 7: 640KB FDD UNIT#3 *1
bit 6: 640KB FDD UNIT#2 *1
bit 5: 640KB FDD UNIT#1 *1
bit 4: 640KB FDD UNIT#0 *1
bit 3: 1MB FDD UNIT#3 *2
bit 2: 1MB FDD UNIT#2 *2
bit 1: 1MB FDD UNIT#1 *2
bit 0: 1MB FDD UNIT#0 *2
1 = Motor stopped or drive not connected
0 = Motor running
*1: Used in 640KB interface mode
*2: Used in 1MB interface mode
Explanation o Indicates the status of the FDD spindle motor. When the built-in dual-purpose FD interface is in 1MB interface mode, the lower 4 bits are used
and the upper 4 bits are always 1111b. When in 640KB interface mode, the upper 4 bits are used and the lower 4 bits are always 1111b.
Related 0000:0485h
0000:05D7h
Memory 0000:05A5h
Type 8bit FLAGS
Name
Classification DISK BIOS
Undocumented
Target PC-H98-B12, PC-9801-92･100, PC-9821X-B02,
Equivalent to the above built-in SCSI interface
Contents NEC SCSI HDD "D5882" identification
------+-----------
Bit | Device
------+-----------
bit 7 | Unused
bit 6 | SCSI ID #6
bit 5 | SCSI ID #5
bit 4 | SCSI ID #4
bit 3 | SCSI ID #3
bit 2 | SCSI ID #2
bit 1 | SCSI ID #1
bit 0 | SCSI ID #0
------+-----------
1 = D5882 is connected
0 = D5882 is not connected
Explanation o The bit corresponding to the SCSI ID of the drive that returns "D5882" to the SCSI command Inquiry will be set to 1.
Related 0000:05AFh
Memory 0000:05A6h
Type 8bit FLAGS
Name CARD_STATUS
Classification PCMCIA
Target PC-9801NL, PC card slot equipped machine
Contents PCMCIA memory card status
bit 7: Access status
1 = Accessing
0 = Not accessing
bit 6: Read/write
1 = Write
0 = Read
* Valid when bit 7=1
bit 5: Card identification
1 = Before card identification
0 = After card identification
* Always 1 when bit 3=0 (no card).
* When MCDRV.SYS is installed in a PC card slot equipped machine or on a PC-9801NL, this bit becomes 0 when bit 3=1 (card present) and the PCMCIA
memory card is accessed with INT 1Fh - Function B4h,B5h (BIOS READ/WRITE).
* If MCDRV.SYS is not installed on a machine with a PC card slot, when bit 3=1 (card present), this bit will not be set to 0 even if you access
the PCMCIA memory card with INT 1Fh - Function B4h (BIOS READ). It will remain at 1.
bit 4: Card swap detection
1 = swapped
0 = not swapped
* Set to 1 as soon as the card is inserted or removed (opened or closed the slot cover on the PC-9801NL).
* When creating device drivers, etc., this can be used to detect card swapping. In other words, the device driver should be created
to set this bit to 0 when it accesses the PCMCIA memory card. If this bit remains 0 the next time you access it, you know that
the card has not been swapped. If it is set to 1, you know that the card has been swapped.
bit 3: Card presence/absence
1 = present
0 = absent
* Set to 1 or 0 as soon as the card is inserted or removed (opened or closed the slot cover on the PC-9801NL).
bit 2: Write protection
1 = Yes
0 = No, no card
* Valid when bit 3=1 (card present).
* Always 1 when bit 0=1 (EMS card).
* Always 1 for ROM card.
bit 1: RAM/ROM card identification
1 = RAM/ROM card
0 = Other
* Valid when bit 5=0 (after card identification)
* However, if MCDRV.SYS is not installed in a machine with a PC card slot, bit 5=0 will not be set. However, after INT 1Fh - Function B4h (BIOS READ)
is executed, this bit will change to a value according to the type of card.
bit 0: EMS card identification
1 = EMS card
0 = Other
* Valid when bit 5=0 (after card identification)
Explanation o Indicates the status of the PCMCIA memory card.
o The operation of each bit differs slightly in the following three types of environments.
- PC-9801NL
- PC card slot equipped machine (MCDRV.SYS not installed)
- PC card slot equipped machine (MCDRV.SYS installed) Differences due to the environment are shown in the "Contents" section.
o On PC-98HA, the same information is stored at 0000:059Eh.
Related 0000:059Eh
Memory 0000:05A7h
Type BYTE
Name
Classification
Target Normal, High-Resolution
Content Unused
Explanation
Related
Memory 0000:05A8h
Type 16bit FLAGS
Name CARD_EQUIP
Classification PCMCIA
Target PC-9801NL, PC card slot
Content PCMCIA memory card BIOS support
bit 15-1: Unused
bit 0: PCMCIA memory card drive
1 = Yes
0 = No
Explanation o Always 1 on PC-9801NL. No corresponding information is stored on PC-98HA.
o On PC card slot-equipped machines, this becomes 1 when MCDRV.SYS is installed. At this time, INT 1Fh - Function B5-B8h become available.
Even if this bit is 0, if the model has a PC card slot, INT 1Fh - Function B4h supported by the BIOS is always available.
Related INT 1Fh - Function B4h
INT 1Fh - Function B5h
INT 1Fh - Function B6h
INT 1Fh - Function B7h
INT 1Fh - Function B8h
Memory 0000:05A9-05ACh
Type 4 BYTES
Name
Classification DISK BIOS
Undocumented
Target PC-9801NA･NS/R･NX/C･P･NL/R･NS/A, PC-9821Ne...
Contents
-------+-------------+----------
Offset | Read | Write
-------+-------------+----------
05A9h | F3h(REPZ) | F3h(REPZ)
05AAh | 6Dh(INSW) | 26h(ES:)
05ABh | CBh(RETF) | 6Fh(OUTSW)
05ACh | | CBh(RETF)
-------+-------------+----------
Explanation o IDE When inputting and outputting to the HDD, in order to
execute I/O string commands at high speed, write the command code here and
execute it by FAR CALL from the BIOS.
Related
Memory 0000:05ADh
Type 8bit FLAGS
Name
Classification Undocumented
Target EMM386.EXE
Contents VDS installation status
bit 7,6: Unused(?)
bit 5: VDS installation status
1 = VDS usable
0 = VDS not usable
bit 4-0: Unused(?)
Explanation o Indicates whether VDS (Virtual DMA Specification:INT 4Bh)
provided by EMM386 is usable. PC-H98-B12 (SCSI interface board) and
PC-9821X-B02 (SCSI-2 interface board) check the installation status of VDS.
Related
Memory 0000:05AEh
Type 8bit FLAGS
Name
Classification DISK BIOS
Undocumented
Target 1.44MB FD I/F supported machine
Contents
■Desktop
bit 7: Unused
bit 6-4: Unknown
* Changes when FDD is accessed.
bit 3-0: 1.44MB supported drive
1 = 1.44MB accessible
0 = 1.44MB inaccessible
------+---------------------
Bit | Device
------+---------------------
bit 3 | unit #3 (DA/UA=33h)
bit 2 | unit #2 (DA/UA=32h)
bit 1 | unit #1 (DA/UA=31h)
bit 0 | unit #0 (DA/UA=30h)
------+---------------------
■98NOTE
bit 7 : Unknown
* Models that set this bit to 1 are PC-9801NS/R･NX/C･P･NL/R.
PC-9801NS/A, PC-9821Ne･Np do not set or reference it in the BIOS.
Bits 6-4: Unused
Bits 3-0: 1.44MB supported drives
* Same as desktop
Explanation u The state of bits 3-0 determines the output result of INT 1Bh - Function C4h (AH bit 3,2).
For drives with a value of 1, AH bit 3,2 = 11b (1.44MB, both) is returned. For drives with a value of 0,
the same processing as INT 1Bh - Function 84h appears to be performed. However, when determining whether
1.44MB can be accessed, it is better to use the BIOS whenever possible.
Related 0000:055Ch
INT 1Bh - Function C4h
I/O 04BEh
Memory 0000:05AFh
Type 8bit FLAGS
Name
Classification DISK BIOS
Undocumented
Target PC-H98-B12, PC-9801-92･100, PC-9821X-B02,
Main body built-in SCSI interface equivalent to the above
Contents Drive identification whose capacity was obtained by the SCSI Read
Capacity command
------+-----------
Bit | Device
------+-----------
bit 7 | Unused *1
bit 6 | SCSI ID #6
bit 5 | SCSI ID #5
bit 4 | SCSI ID #4
bit 3 | SCSI ID #3
bit 2 | SCSI ID #2
bit 1 | SCSI ID #1
bit 0 | SCSI ID #0
------+-----------
1 = Drive whose capacity was obtained by the SCSI Read Capacity command
0 = Drives that obtained capacity using the PC-9801-55 original L/U compatible method
*1: In the PC-H98-B12, this is used as some kind of flag. Details unknown.
Explanation o SCSI interface boards from PC-H98-B12 onwards allow the connection of HDDs made by manufacturers other than NEC. When a drive made by
a manufacturer other than NEC is connected, the bit of the corresponding SCSI ID at this address becomes 1.
However, the check to see if it is made by NEC is not done by checking the vendor ID obtained with the SCSI Inquiry command.
u When a HDD made by a manufacturer other than NEC is connected, the total capacity of the drive is obtained with the SCSI Read Capacity command,
and the number of cylinders is calculated assuming the number of heads = 08h and the number of sectors = 20h. This value is written to the
"SCSI device parameter table" at 0000:0460h.
Related 0000:0460h
0000:0482h
0000:05A5h
References Takeshi Kono, "Attempt to connect a junk hard disk to an old type NEC genuine SCSI," TheBASIC, August 1994 issue (Gijutsuhyoronsha)
Memory 0000:05B0h
Type 8bit FLAGS
Name IDE HDD capacity type
Classification IDE HD
Undocumented
Target IDE-equipped machine
Contents IDE drive capacity (2)
--------+---------------------------
Bit | Contents
--------+---------------------------
Bit 7 | 0 (unused)
Bit 6 | 0 (unused)
Bit 5-3 | 1st IDE HD capacity
Bit 2-0 | 2nd IDE HD capacity
--------+---------------------------
---------------+------------
Capacity value | Drive capacity
---------------+------------
000b | 0000:0457h indicates capacity
001b | 240MB
010b | 500MB
011b | 170MB
100b | 340MB
111b | No drive
---------------+------------
Explanation o IDE Indicates the capacity of the HD.
u The supported range of values indicating drive capacity varies depending on the model.
u Some models equipped with IDE BIOS do not use this work.
Related 0000:0457h
Memory 0000:05B1-05B2h
Type WORD
Name
Classification DISK BIOS
Undocumented
Target PC-9821Bp, Bs, Be, Bf, Ts, Cs2, Ce2, Xa, Xn, Xp, Xs, Xe,
PC-9801BA2, BS2, BX2, BA3, BX3, BX4
Contents Motor stop time counter for second IDE hard disk (unit: 100ms)
Explanation o When "Built-in fixed disk control set", this address is used to count the motor stop time.
When this value is decremented to 0000h, the HDD spindle motor stops.
o When "Built-in fixed disk control not set", it is always 0000h.
o The INT 17h handler decrements.
Related 0000:04FEh
0000:0598h
0000:059Ah
0000:058Ch
0000:058Eh
INT 17h (External interrupt...IDE)
INT 1Bh - Function D0h (IDE)
INT 1Bh - Function E0h (IDE)
INT 1Bh - Function F0h (IDE)
Memory 0000:05B3h
Type 8bit FLAGS
Name
Classification PRINTER BIOS
Undocumented
Target IEEE STD 1284 equipped machines
Content
bit 7: IEEE STD 1284 (bidirectional printer interface) support
1 = Supported
0 = Not supported
* When a 98 Hi-Res board (PC-9821A-E02) is installed in a PC-9821Ap2/As2/An,
only the printer interface on the 98 Hi-Res board side is enabled, so this
bit is set to 0 (not supported) in both normal and high-res modes.
bit 6,5: IEEE STD 1284 mode
01b = Input/output mode
00b = Compatible mode
* Bit 6 is always 0
* When in input/output enabled mode, 0000:0458 bit 2 is always 1.
bit 4-1: Unused
bit 0: Unknown
Explanation o Indicates the status of the IEEE STD 1284 compliant printer interface.
Related 0000:0458h bit 2,1
INT 1Ah - Function 17h
INT 1Ah - Function 19h
INT 1Ah - Function 1Ah
INT 1Ah - Function 1Bh
Memory 0000:05B4-05B5h
Type 2 BYTES
Name
Classification Display Suspend BIOS
Undocumented
Target DPMS-compatible devices
Contents CRT state before transition to suspend mode
0000:05B4h : Contents of I/O 006Ch before transition to suspend mode
0000:05B5h : Screen display state before transition to suspend mode
01h = Screen display in progress (OUT 68h,0Fh state)
00h = Screen display stopped (OUT 68h,0Eh state)
Explanation o INT 1Fh - Stores the CRT state before transition to suspend mode when suspend mode is set with Function 93h.
Related INT 1Fh - Function 93h
I/O 0068h - 0Eh,0Fh
I/O 006Ch
Memory 0000:05B6h
Type BYTE
Name
Classification
Target
Content Unused
Explanation
Related
Memory 0000:05B7h
Type BYTE
Name READ_DATA port address
Classification Plug and Play
Undocumented
Target Plug and Play compatible devices
Content PCI READ_DATA port address
Explanation o Indicates the address of the READ_DATA port used in C-bus Plug and Play.
o The value of this work is shifted 2 bits to the left and the lower 2 bits are set to 11b to become the READ_DATA port.
Figure --------------------------------+----------------------------
Value of this work area | xxxx xxxxb
| / /
READ_DATA port address | 0000 00xx xxxx xx11b
--------------------------------+----------------------------
Related I/O 0003-03FFh
I/O 0259h,0A59h - 00h
Memory 0000:05B8h
Type BYTE
Name Number of C bus PnP boards
Classification Plug and Play
Undocumented
Target Plug and Play compatible device
Content Number of C bus PnP boards
Explanation o Indicates how many boards compatible with C bus Plug and Play are installed. Refer to this when checking the
maximum value that can be set as CSN (Card Select Number).
o When the value of this work is 00h, it indicates that no C bus Plug and Play compatible boards are being used.
Related I/O 0259h,0A59h - 03h
Memory 0000:05B9-5BFh
Type 7 BYTES
Name
Classification
Target
Content Unused
Explanation
Related
Memory 0000:05C0h
Type 8bit FLAGS
Name BASIC_DIPSW
Category N88 BASIC
Target Normal, High Resolution, PC-98LT/HA
Contents Copy of DIP SW 2 setting
bit 7: DIP SW 2-8
bit 6: DIP SW 2-7
bit 5: DIP SW 2-6
bit 4: DIP SW 2-5
bit 3: DIP SW 2-4
bit 2: DIP SW 2-3
bit 1: DIP SW 2-2
bit 0: DIP SW 2-1
1 = OFF
0 = ON
Explanation o When the BASIC interpreter (ROM version, DISK version, MS-DOS version) starts, it reads the state of DIP SW 2 from the system port (I/O
0031h) and writes it to this address. 00h when the system starts.
Related I/O 0031h
Memory 0000:05C1h
Type 8bit FLAGS
Name RS_D_FLAG
Category RS-232C
Target Normal, High Resolution, PC-98LT/HA
Contents Processing when receiving RS-232C DEL (7Fh, FFh) code
bit 7-3: Unused
bit 2: CH 2
bit 1: CH 1
bit 0: CH 0
1 = Follow the setting of memory switch 3 - bit 7
0 = Store DEL (7Fh, FFh) code directly in the buffer
Explanation o Used by N88BASIC (ROM version, DISK version, MS-DOS version) and terminal mode. Determines the processing when the DEL (7Fh, FFh) code is
received over RS-232C. Referenced by the RS-232C external interrupt handler. o In the high-resolution mode RS-232C BIOS, in extended mode,
you can specify how to handle the received DEL (7Fh/FFh) code, but the setting is not reflected in this flag and is stored in the buffer
control block. The RS-232C BIOS (INT 19h) does not set this flag. Only N88BASIC and terminal mode set this flag.
However, the RS-232C external interrupt handler in ROM always references this flag for processing.
Related 0000:0556h
0000:055Bh
0000:05F0h
0000:05F4h
INT 0Ch (External interrupt...RS-232C)
Memory 0000:05C2-05C5h
Type DWORD
Name GPIB_WORK
Category GP-IB
Target PC-9801-06, 19, 29 original, 29K, 29N
Contents Pointer to GP-IB control information notification area
Explanation o Stores the address of the control information notification area used by the GP-IB BIOS.
Related INT D1h
I/O 0099h
Memory 0000:05C6-05C9h
Type DWORD
Name KB_CODE
Category KEYBOARD BIOS
Target Normal (except for the first generation PC-9801), PC-98LT, HA, DB-P1
Contents First address of the key data conversion table
Explanation o First address of the conversion table used when generating key data from the key number and shift state.
u The contents of this address only indicate the beginning of the conversion table in ROM, and rewriting this content does not
change the conversion table referenced by the keyboard BIOS (keyboard interrupt handler). However, since the keyboard interrupt
handler references the segment value written at this address, changing this will cause the keyboard BIOS to malfunction.
Changing the offset value does not affect the operation of the keyboard BIOS.
Related 0000:0414h
0000:0522h
Memory 0000:05C6-05C9h
Type DWORD
Name
Classification Undocumented
Target PC-H98 (Hi-Res)
Content Unknown.
Explanation o In the Hi-Res mode of the PC-H98, FD80:0A94h is set. Since FD80h is not used as a segment in Hi-Res mode,
and there is no table starting from FD80:0A94h, this is not considered to be a particularly meaningful value.
Related
Memory 0000:05CAh
Type 8bit FLAGS
Name F2DD_MODE
Classification DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode
Contents 640KB FDD access mode
[INT 1Bh - Function 8Eh(FD) setting]
bit 7: 640KB FDD UNIT#3
bit 6: 640KB FDD UNIT#2
bit 5: 640KB FDD UNIT#1
bit 4: 640KB FDD UNIT#0
1 = 80 cylinders (2DD,1DD)
0 = 40 cylinders (2D,1D)
[INT 1Bh - Function 0Eh(FD) setting]
bit 3: 640KB FDD UNIT#3
bit 2: 640KB FDD UNIT#2
bit 1: 640KB FDD UNIT#1
bit 0: 640KB FDD UNIT#0
1 = Double-sided
0 = Single-sided
Initial value = FFh (2DD/Double-sided)
Explanation o Stores the setting value of INT 1Bh - Function 0Eh, 8Eh in 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode.
Related 0000:0493h
INT 1Bh - Function 03h(FD)
INT 1Bh - Function 04h(FD)
INT 1Bh - Function 84h(FD)
INT 1Bh - Function 0Eh(FD)
INT 1Bh - Function 8Eh(FD)
Memory 0000:05CBh
Type BYTE
Name F2DD_COUNT
Classification DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode,
dual-use BIOS - 1MB I/F mode (excluding PC-9801VM2/VM21/UV2/UV21/VX2/VX21, PC-98XA/XL)
Content Initial value of FDD spindle motor stop time (unit: 100ms)
Initial value = 96h (15 seconds: Desktop, PC-9801N/NS)
14h (2 seconds: 98NOTE other than PC-9801N/NS)
Explanation o When disk I/O ends, this value is copied to the motor stop counter.
The address of the motor stop counter is 0000:0485h in dual-use BIOS - 1MB I/F mode,
and 0000:05D7h in 640KB dedicated BIOS and dual-use BIOS - 640KB I/F mode.
o In dual-use BIOS - 1MB I/F mode, it is only valid on models with motor stop control
function (PC-9801VM2, VM21, UV2, UV21, VX2, VX21, PC-98XA, excluding dual-use FD I/F).
In dual-use BIOS - 640KB I/F mode, it is valid on all models equipped with dual-use FD I/F.
o The ON/OFF state of the motor stop mode at startup differs depending on the model.
Some models have the motor stop mode OFF at startup, some can be selected from the menu,
and some are ON from startup.
o It is set to the initial value when INT 1Bh - Function 03h (FD) (FD interface initialization) is executed.
In machines with dual-use BIOS, the value of this address is set to the
initial value regardless of whether the motor stop mode is set or not. The
motor stop mode status cannot be determined from this value.
Related 0000:0485h
0000:05D7h
INT 1Bh - Function 03h(FD)
INT 1Bh - Function 83h(FD)
I/O 00BEh
Memory 0000:05CC-05CFh
Type DWORD
Name F2DD_POINTER
Category DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB access mode
Contents 640KB FDD parameter table pointer address
[640KB FDD parameter table pointer address]
-----------+-----------------------------------------------------
Address | Contents
-----------+-----------------------------------------------------
0000:05CCh | 640KB FD parameter table pointer offset (nnnnh)
0000:05CEh | 640KB FD parameter table pointer segment (ssssh)
-----------+-----------------------------------------------------
o The default value of the segment is FD80h, and the default value of the
offset varies depending on the model.
[640KB FD parameter table pointer]
-------------+--------------------------------------------------------
Address | Contents
-------------+--------------------------------------------------------
ssss:nnnnh+0 | 640KB FDD UNIT#0 parameter table offset (mmmmh)
ssss:nnnnh+2 | 640KB FDD UNIT#1 parameter table offset (mmmmh)
ssss:nnnnh+4 | 640KB FDD UNIT#2 parameter table offset (mmmmh)
ssss:nnnnh+6 | 640KB FDD UNIT#3 parameter table offset (mmmmh)
-------------+--------------------------------------------------------
[640KB FDD UNIT#0 to #3 parameter table]
+--------------+---------------+---------------+---------------------+
| | MFM | FM | |
| +-------+-------+-------+-------+ |
| Address | R/W | Format| R/W | Format| Remarks |
| +---+---+---+---+---+---+---+---+ |
| |EOT|GPL| SC|GPL|EOT|GPL| SC|GPL| |
+--------------+---+---+---+---+---+---+---+---+---+-----------------+
|ssss:mmmmh+00h|00h|00h|00h|00h|10h|07h|10h|1Bh|1 sector = 128 bytes |
|ssss:mmmmh+08h|10h|0Eh|10h|36h|09h|0Eh|09h|2Ah|1 sector = 256 bytes |
|ssss:mmmmh+10h|09h|2Ah|09h|50h|05h|1Bh|05h|3Ah|1 sector = 512 bytes |
|ssss:mmmmh+18h|05h|35h|05h|74h|00h|00h|00h|00h|1 sector = 1024 bytes|
+--------------+---+---+---+---+---+---+---+---+--+------------------+
o No parameters are set because 128 bytes/sector of MFM and 1024 bytes/sector of FM cannot be used.
o The segment of the parameter table is the same as the segment of the pointer table.
Explanation o This indicates the address of the parameter table pointer used when formatting and writing to a 640KB format floppy disk.
Although a pointer is prepared for each unit, they all actually point to the same table.
u On 1.44MB-compatible machines, if the pointer table segment is changed to a value other than the default
(normal = FD80h, high-res = F800h), problems will occur when accessing a 1.44MB disk. In other words, when a 1.44MB disk is
accessed with DA/UA=3xh, the value of 0000:05CEh is used as the segment of the parameter table for the 1.44MB FDD.
Since the offset of the parameter table for a 1.44MB FDD is fixed, the correct parameter table will not be used.
However, since there is usually no need to change the value of 0000:05CEh, this behavior is unlikely to cause any problems.
Related 0000:05F8h
Memory 0000:05D0-05D6h
Type 7 BYTES
Name F2DD_RESULT
Classification DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode
Contents 640KB FD I/F FDC result status (READ/WRITE commands)
----------+---------------------------------------------
Address | Contents
----------+---------------------------------------------
05D0h | ST0 (Result Status)
| bit 7: IC1 (Interrupt Code 1)
| bit 6: IC0 (Interrupt Code 0)
| bit 5: SE (Seek End)
| bit 4: EC (Equipment check)
| bit 3: NR (Not Ready)
| bit 2: HD (Head Address)
| bit 1: US1 (Unit Select 1)
| bit 0: US0 (Unit Select 0)
----------+---------------------------------------------
05D1h | ST1(Result Status)
| bit 7: EN(End of Cylinder)
| bit 6: 0
| bit 5: DE(Data Error)
| bit 4: OR(Overrun)
| bit 3: 0
| bit 2: ND(No Data)
| bit 1: NW(Not Writable)
| bit 0: MA(Missing Address Mark)
-----------+---------------------------------------------
05D2h | ST2(Result Status)
| bit 7: 0
| bit 6: CM(Control Mark)
| bit 5: DD(Data Error in Data Field)
| bit 4: NC(No Cylinder)
| bit 3: SH(Scan Equal Hit)
| bit 2: SN(Scan Not Satisfied)
| bit 1: BC(Bad Cylinder)
| bit 0: MD (Missing Address Mark in Data Field)
-----------+---------------------------------------------
05D3h | C (Cylinder number)
05D4h | H (Head number)
05D5h | R (Record number)
05D6h | N (Data length)
-----------+---------------------------------------------
Explanation o Status information returned from the FDC (μPD765A) when disk I/O is completed. The results of READ/WRITE commands are stored here.
o In dual-use FD I/F, this work area is used even in 1MB access mode if the I/F mode is 640KB.
Related 0000:0564h
0000:05D8h
I/O 00C8h
Memory 0000:05D7h
Type BYTE
Name F2DD_RESULT
Category DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode
Contents Motor stop counter (unit: 100ms)
Explanation o Counter for measuring the time until the motor stops.
u When disk I/O ends, the value of 0000:05CBh (initial value of motor stop time) is copied.
The value is decremented by 1 by an interrupt that occurs every 100ms with FDC, and when it reaches 0, the motor stops.
Related 0000:0485h
0000:05A4h
0000:05CBh
I/O 00C8h
Memory 0000:05D8-05DFh
Type 8 BYTES
Name F2DD_RESULT
Classification DISK BIOS
Target 640KB dedicated BIOS, dual-use BIOS - 640KB I/F mode
Contents 640KB FD I/F FDC result status (SEEK/RECALIBRATE command)
05D8h: UNIT#0 ST0 (Result status)
05D9h: UNIT#0 PCN (Present cylinder number)
05DAh: UNIT#1 ST0 (Result status)
05DBh: UNIT#1 PCN (Present cylinder number)
05DCh: UNIT#2 ST0 (Result status)
05DDh: UNIT#2 PCN (present cylinder number)
05DEh: UNIT#3 ST0 (result status)
05DFh: UNIT#3 PCN (present cylinder number)
Explanation o Status information returned from FDC (μPD765A) when disk I/O is completed. The result of SEEK/RECALIBRATE command is stored.
The contents of ST0 (result status) are the same as 0000:05D0h.
o In dual-use FD I/F, this work area is used even in 1MB access mode if in 640KB I/F mode.
Related 0000:0564h
0000:05D0h
I/O 00C8h
Memory 0000:05E0-05E3h
Type DWORD
Name MUSIC_WORK
Classification SOUND
Target PC-9801-14, PC-9801-26 first generation/K, PC-9801-73/86
(including built-in type equivalent to the above board) ROM BIOS installed
Content Start address of work area for music BIOS/sound BIOS
Explanation o Stores the start address of the work area for music BIOS (PC-9801-14 ROM BIOS installed with music generator board) and
sound BIOS (PC-9801-26 first generation/K, PC-9801-73/86 ROM BIOS installed with sound board).
u In the music BIOS in the BIOS ROM installed in the PC-98XA, the work area segment is stored at 0000:05E0h (WORD).
Other high-resolution machines do not support music BIOS (no high-resolution machines support sound BIOS).
Related INT D2h
I/O 008Eh
I/O 0188h
Memory 0000:05E4h
Type BYTE
Name
Classification
Target
Content Unused
Explanation
Related
Memory 0000:05E5h
Type BYTE
Name
Classification BRANCH4670
Undocumented
Target PC-9864 first generation/U, PC-98XA/XL/XL^2/RL high-resolution mode BRANCH BIOS
Content Unknown
Initial value=40h
Explanation o Details unknown
Related 0000:0400h bit 0
0000:041E-0443h
0000:0480h bit 5
0000:049A-04ABh
Memory 0000:05E6h
Type BYTE
Name
Classification BRANCH4670
Undocumented
Target PC-9864 first generation/U, PC-98XA/XL/XL^2/RL high-resolution mode BRANCH BIOS
Content Host station number (00-3Fh)
Initial value = 00h
Explanation o In PC-9864-02 (original PC-9864 ROM BIOS), it tests bit 6 of memory switch 7, and if it is 1, it ANDs that value with 3Fh and writes it to 0000:05E6h.
Related 0000:0400h bit 0
0000:041E-0443h
0000:0480h bit 5
0000:049A-04ABh
A000:3FFAh
E000:3FFAh
Memory 0000:05E7h
Type BYTE
Name
Classification BRANCH4670
Undocumented
Target PC-9864U + Normal
Contents Station number of own station
Explanation o Details unknown. Used in relation to the remote printer at INT 1Ah.
Related 0000:0400h bit 0
0000:041E〜0443h
0000:0480h bit 5
0000:049A〜04ABh
Memory 0000:05E8-05EBh
Type DWORD
Name DISK_PRM0
Classification DISK BIOS
Undocumented
Target SASI, IDE equipped devices (both normal and high resolution)
Contents First address of SASI/IDE HD #0 parameter table
Explanation o Stores the first address of the drive control parameter table.
When the mode setting function (INT 1Bh - Function 0Eh (SASI/ESDI/IDE)) is executed, the address of this parameter table may change.
o The contents of the parameter table are not compatible between SASI HD and IDE HD.
Table SASI HD Parameter Table Contents
--------------+-----------------------------------------------------------
Offset (size) | Contents
--------------+-----------------------------------------------------------
+00h (BYTE) | Step pulse width
+01h (BYTE) | Step interval
+02h (BYTE) | Step mode
+03h (BYTE) | Maximum head address
+04h (WORD) | Maximum cylinder address (High byte, Low byte order)
+06h (BYTE) | Write current reduction address
+07h (BYTE) | Overlap seek flag (bit 6)
+0Ah (BYTE) | Step pulse width
+0Bh (BYTE) | Step interval
+0Ch (BYTE) | Step mode
+0Dh (BYTE) | Maximum head address
+0Eh (WORD) | Maximum cylinder address 2 (High byte, Low byte order)
+10h (BYTE) | Write current reduction address
+11h (BYTE) | Overlap seek flag (bit 6)
+14H (BYTE) | Value returned to AH by SENSE(INT 1Bh - Function 04h(SASI/ESDI/IDE))
+18H (WORD) | Number of heads (used for INT 1Bh physical address to logical address conversion)
+1CH (BYTE) | Value returned to AH by new SENSE(INT 1Bh - Function 84h(SASI/ESDI/IDE))
--------------+-----------------------------------------------------------
Table Contents of IDE HD parameter table
--------------+-----------------------------------------------------------
Offset(size) | Contents
--------------+-----------------------------------------------------------
+00h (WORD) | Number of cylinders (output CX of INT 1Bh - Function 84h(SASI/ESDI/IDE))
+02h (BYTE) | Number of heads (INT 1Bh - Function 84h (SASI/ESDI/IDE) output DH)
+03h (BYTE) | Number of heads returned by the drive (used for logical address conversion)
+04h (BYTE) | Capacity value (INT 1Bh - Function 04h (SASI/ESDI/IDE) output AH)
+05h (BYTE) | Capacity value (INT 1Bh - Function 84h (SASI/ESDI/IDE) output AH)
--------------+-----------------------------------------------------------
Related 0000:0481h bit 0
0000:05ECh
INT 1Bh - Function 04h (SASI/ESDI/IDE)
INT 1Bh - Function 84h (SASI/ESDI/IDE)
INT 1Bh - Function 0Eh (SASI/ESDI/IDE)
Memory 0000:05EC-05EFh
Type DWORD
Name DISK_PRM1
Category DISK BIOS
Undocumented
Target SASI, IDE equipped devices (both normal and high resolution)
Content First address of parameter table for SASI/IDE HD #1
Explanation o Same as 0000:05E8h.
Related 0000:0481h bit 1
0000:05E8h
INT 1Bh - Function 04h (SASI/ESDI/IDE)
INT 1Bh - Function 84h (SASI/ESDI/IDE)
INT 1Bh - Function 0Eh (SASI/ESDI/IDE)
Memory 0000:05F0-05F3h
Type DWORD
Name RS_CH1_OFST/SEG
Category RS-232C BIOS
Target Hi-Res, RSDRV.SYS
Content RS-232C CH1 receive buffer pointer
Explanation o Stores the address of the receive buffer for RS-232C CH1. Used by the RS-232C BIOS (INT 19h) and RSDRV.SYS in Hi-Res mode.
Related 0000:0556h
0000:055Bh
0000:05C1h
0000:05F4h
INT 19h - Function 00h (BIOS)
Memory 0000:05F4-05F7h
Type DWORD
Name RS_CH2_OFST/SEG
Category RS-232C BIOS
Target Hi-Res, RSDRV.SYS
Content RS-232C CH2 receive buffer pointer
Explanation o Stores the address of the receive buffer for RS-232C CH2. Used by the RS-232C BIOS (INT 19h) and RSDRV.SYS in Hi-Res mode.
Related 0000:0556h
0000:055Bh
0000:05C1h
0000:05F0h
INT 19h - Function 00h(BIOS)
Memory 0000:05F8-05FBh
Type DWORD
Name F2HD_POINTER
Category DISK BIOS
Target 1MB dedicated BIOS, dual-use BIOS - 1MB access mode
Contents 1MB FDD parameter table pointer address
[1MB FDD parameter table pointer address]
-----------+------------------------------------------------------
Address | Contents
-----------+------------------------------------------------------
0000:05F8h | 1MB FD parameter table pointer offset (nnnnh)
0000:05FBh | 1MB FD parameter table pointer segment (ssssh)
-----------+------------------------------------------------------
o The default value of the segment is FD80h, and the default value of the
offset varies depending on the model.
[1MB FD Parameter Table Pointer]
-------------+-------------------------------------------------------
Address | Contents
-------------+-------------------------------------------------------
ssss:nnnnh+0 | 1MB FDD UNIT#0 Parameter Table Offset (mmmmh)
ssss:nnnnh+2 | 1MB FDD UNIT#1 Parameter Table Offset (mmmmh)
ssss:nnnnh+4 | 1MB FDD UNIT#2 Parameter Table Offset (mmmmh)
ssss:nnnnh+6 | 1MB FDD UNIT#3 Parameter Table Offset (mmmmh)
-------------+-------------------------------------------------------
[1MB FDD UNIT#0 to #3 Parameter Table]
--------------+---------------+---------------+----------------------
| MFM | FM |
+-------+-------+-------+-------+
Address | R/W | Format| R/W | Format| Notes
+---+---+---+---+---+---+---+---+
|EOT|GPL| SC|GPL|EOT|GPL| SC|GPL|
--------------+---+---+---+---+---+---+---+---+---+---+---------------
ssss:mmmmh+00h|00h|00h|00h|00h|1Ah|07h|1Ah|1Bh|1 sector=128 bytes
ssss:mmmmh+08h|1Ah|0Eh|1Ah|36h|0Fh|0Eh|0Fh|2Ah|1 sector=256 bytes
ssss:mmmmh+10h|0Fh|1Bh|0Fh|54h|08h|1Bh|08h|3Ah|1 sector=512 bytes
ssss:mmmmh+18h|08h|35h|08h|74h|00h|00h|00h|00h|1 sector=1024 bytes
--------------+---+---+---+---+---+---+---+---+---+-------------------
o Parameters are not set because 128 bytes/sector of MFM and 1024 bytes/sector of FM cannot be used.
o The segment of the parameter table is the same as the segment of the pointer table.
Explanation o Indicates the address of the parameter table pointer used when formatting and writing to a 1MB format floppy disk.
A pointer is provided for each unit, but all of them actually point to the same table.
u On 1.44MB-compatible machines, if the pointer table segment is changed to a value other than the default
(normal = FD80h, high-res = F800h), problems will occur when accessing a 1.44MB disk. In other words, when a
1.44MB disk is accessed with DA/UA=Bxh, the value 0000:05FAh is used as the parameter table segment of the 1.44MB FDD.
Since the offset of the parameter table of a 1.44MB FDD is fixed, the correct parameter table will not be used.
However, since there is usually no need to change the value of 0000:05FAh, this behavior is unlikely to cause any problems.
Related 0000:05CCh
Memory 0000:05FC-05FDh
Type WORD
Name MOUSEW
Category MOUSE BIOS
Target Hi-Res
Contents Segment address of mouse BIOS work area
Explanation o Stores the segment of the work area used by the mouse BIOS (INT 33h) in Hi-Res mode.
Related F800:7FD0h
INT 33h - Function 11h
Memory 0000:05FE-05FFh
Type WORD
Name BASIC_WORK
Category BASIC
Target Normal, Hi-Res, PC-98LT/HA
Contents BASIC LIO DATA segment address
Explanation o Stores the BASIC LIO DATA segment address when N88-BASIC is running. In the child process of the MS-DOS version of N88-BASIC,
this address has a value other than 0, and N88BASIC cannot be started again.
Related