Copyright(C) 1994,1995,1996,1997 Terumasa KODAKA , Takeshi KONO
■IDE interface
Basic knowledge
o List of devices with built-in IDE interface
-----------------------------------------------+--------------------------------------------
| Model
-----------------------------------------------+--------------------------------------------
2.5", 1.8" IDE built-in HD (not removable) | PC-9801NS･UR･P･NL/R･NL/A, PC-9821Ld
2.5" IDE (pack for PC-9801NS/L) | PC-9801NS/L
2.5" IDE (hard disk pack available for 98NOTE) | 98NOTE (excluding PC-9801N/NV/NL and the above 98NOTE)
| PC-9801US, PC-H98T, PC-9821 first generation・Ce・Ts・Es
Up to 1 3.5" IDE | PC-9821Ap･As･Ae･Af･Ap2･As2･An･Cs2･Ce2･
| Cf･Cx･Cb･Xt13･Cx2･Cb2, PC-9801BA･BX
Up to 2 3.5" IDE | PC-9821Ap3･As3･Bp･Bs･Be･Bf･
| Xa･Xf･Xn･Xp･Xs･Xe･Xe10･
| PC-9801BA2･BS2･BX2･BX3･BX4
Up to 4 3.5" IDE | PC-9821Xa16･Xa13･Xa12･Xa10･Xa9･Xa7･Xa7e
| Xv13・Xb10
-----------------------------------------------+--------------------------------------------
* For PC-9821Cs2･Ce2･Cf･Cx･Cb･Cx2･Cb2, CD-ROM is connected as the second IDE.
* For machines equipped with file bays, a CD-ROM or HDD can be connected as a second IDE.
o The BIOS interface of IDE hard disks is compatible with SASI hard disks. For this reason,
PC-9801-27 (SASI I/F board) cannot be used with a main unit equipped with an IDE hard disk.
However, if an IDE hard disk is not installed, the PC-9801-27 can be used even with models
that have a built-in IDE interface.
o For models with a built-in IDE interface, when an IDE hard disk is installed, the IDE BIOS is
mapped to the expansion ROM area D8000 to D9FFFh, and the IDE BIOS work area is mapped to DA000
to DBFFFh. If an IDE hard disk is not installed, the IDE BIOS will not be mapped, so it can be
used as an expansion ROM area or UMB. However, on machines equipped with 98NOTE and PCI slots,
D8000 to DBFFFh cannot be used as an expansion ROM area or UMB even if an IDE hard disk is not
installed. In 98NOTE, the BIOS for system control is located in this area. This is because PCI BIOS
is installed on machines equipped with PCI slots.
o The external interrupt of the IDE interface is fixed to INT3 (INT 11h). Also, the PC-9800's IDE
interface does not use DMA for data transfer with the IDE drive.
u PC-9800 does not use the IDE's Master/Slave switching. Switching between the first and second drives
is done by switching all the I/O ports used by the drives using an external circuit.
o The I/O addresses used by the IDE interface are as follows.
------------+-------+-----+----------------------------+-------------------------------------
I/O address | Width | R/W | Content | I/O address in ISA
------------+-------+-----+----------------------------+-------------------------------------
0430h | BYTE | R/W | IDE drive switching | None
0432h | BYTE | R/W | IDE drive switching | None
0435h | BYTE | R/W | Unknown | None
0640h | WORD | R/W | Data Register | 01F0h
0642h | BYTE | R | Error Register | 01F1h
0642h | BYTE | W | Write Precomp Register | 01F1h
0644h | BYTE | R/W | Sector Count | 01F2h
0646h | BYTE | R/W | Sector Number | 01F3h
0648h | BYTE | R/W | Cylinder Low | 01F4h
064Ah | BYTE | R/W | Cylinder High | 01F5h
064Ch | BYTE | R/W | SDH Register | 01F6h
064Eh | BYTE | R | Status Register | 01F7h
064Eh | BYTE | W | Command Register | 01F7h
074Ch | BYTE | R | Alternate Status Register | 03F6h
074Ch | BYTE | W | Digital Output Register | 03F6h
074Eh | BYTE | R | Digital Input Register | 03F7h
------------+-------+-----+----------------------------+-------------------------------------
* The "I/O address in ISA" column is the I/O address used by the IDE drive connected to the IBM PC/AT compatible machine.
Related 0000:0457h
0000:055Ch
0000:0598h
0000:059Ah
0000:05B0h
0000:05B1h
0000:05E8h
0000:05ECh
D800:0000～D800:1FFFh
DA00:0000～DA00:1FFFh
INT 11h (external interrupt)
INT 1Bh(IDE)
I/O 000Ah bit 1
I/O 0430h
Name IDE bank switching
Undocumented
Target (2 devices can be connected) IDE I/F equipped machine
Chip IDE area
Function
[READ/WRITE]
bit 7～0: unknown
00h=IDE bank #1
01h=IDE bank #2
Explanation o Details unknown
Related I/O 0432h
I/O 0432h
Name IDE bank switching
Undocumented
Target (2 devices can be connected) IDE I/F equipped machine
Chip IDE area
Function
[READ/WRITE]
bit 7～0: Bank selection
80h=Dummy write for status reading ([WRITE] only)
00h=IDE bank #1 selection
01h=IDE bank #2 selection
Explanation o Select the IDE bank to be controlled by I/O 0640~064Eh, 074Ch, 074Eh.
o On the PC-9800, bank selection is done by an external circuit connected to this port, which switches the entire drive's I/O ports.
Related I/O 0430h
I/O 0435h
Name Unknown
Undocumented
Target PC-9821An･Ap3･As3･Cf･Cx･Cb･Xa10･Xa9･Xa7･Cx2･Cb2･Xt13･Xe10･Xa12･Xa7e, PC-9801BX4
Function
[READ/WRITE]
bit 7~2: unknown
bit 1: unknown
1=No IDE HDD
0=IDE HDD present
bit 0: unknown
Explanation o Bit 1 is set depending on the presence or absence of an IDE HDD, but details are unknown.
Related I/O 00F0h bit 5
I/O 0640h
Name Data Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 15~0: data register
Explanation o Perform data transfer. The data register width is 16 bits.
I/O 0642h
Name Error Register,Write Precomp Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ] Error Register
bit 7: Bad Block Detected
1=Bad Block mark detected in ID field
0=normal
bit 6: Data ECC Error
1=An unrecoverable ECC error occurred in the data area
0=normal
bit 5: Media changed
1=media replaced
0=media not replaced
*Do not use PC-9800
bit 4: ID Not Found
1=ID not found
0=normal
bit 3: Media Change Requested
1=Media replacement required
0=Media replacement not requested
*Do not use PC-9800
bit 2: Aborted Command
1=Command execution was interrupted
0=normal
bit 1: Track0Error
1=Track0 could not be detected during Restore command execution
0=normal
bit 0: Address Mark Not Found
1=Address mark in data area could not be found
0=normal
Explanation o Obtain the error status of the IDE drive
[WRITE] Write Precomp Register
44h=ECC length for Read/Write Long command 7 bytes
55h=Read Ahead Cache ON
AAh=Read Ahead Cache OFF
BBh=ECC length for Read/Write Long command 4 bytes
Explanation o Configure various settings for the IDE drive.
I/O 0644h
Name Sector Count
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 7～0: Sector Count
Description o Set the number of sectors.
o Specifying 00h behaves as if 256 were specified.
I/O 0646h
Name Sector Number
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 7～0: Sector Number
Description o Set the sector number.
I/O 0648h
Name Cylinder Low
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 7〜0: Cylinder Low
Description o Set the lower 8 bits of the cylinder number.
Related I/O 064Ah
I/O 064Ah
Name Cylinder High
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 7〜0: Cylinder High
Description o Set the upper 8 bits of the cylinder number.
Related I/O 0648h
I/O 064Ch
Name SDH Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ/WRITE]
bit 7: Unused (set to 1)
bit 6: Binary Encoded Address Mode Select
1=Logical Block Address
0=Cylinder/Head/Sector
* Normally set to 0 on PC-9800
bit 5: Unused (set to 1)
bit 4: Drive Select
* Always set to 0 on PC-9800
bit 3～0: Head Select
Explanation o Specify the head number
u The PC-9800 does not use LBA addressing.
Related I/O 074Eh
I/O 064Eh
Name Status Register,Command Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ] Status Register
bit 7: Controller Busy
1=Controller is BUSY
0=normal
bit 6: Drive Ready
1=Drive is in READY state
0=normal
bit 5: Write Fault
1=A write error occurred.
0=normal
bit 4: Seek Complete
1=Seek operation completed successfully
0=Seek operation terminated abnormally
bit 3: Data Request
1=Drive is ready to transfer data
0=Drive is not ready to transfer data
bit 2: Corrected Data
1=A read error occurred but was corrected by ECC
0=normal
bit 1: Index
* Pulse output once per rotation of the disk
bit 0: Error
1=Some error occurred during command processing
0=normal
Explanation o Obtain various statuses.
[WRITE] Command Register
00h= Get drive Feature byte
1xh= Recalibrate
20h= Read(with Retries)
21h= Read(without Retries)
22h= Read Long(with Retries)
23h= Read Long(without Retries)
30h= Write(with Retries)
31h= Write(without Retries)
32h= Write Long(with Retries)
33h= Write Long(without Retries)
3Ch= Write verify
40h= Read Verify(with Retries)
41h= Read Verify(without Retries)
50h= Format Track
7xh= Seek
8xh= Vendor Unique
90h= Execute Drive Diagnostic
91h= Initialize Drive Parameters
94h= Standby Immediate
95h= Idle Immediate
96h= Standby
97h= Idle
98h= Check Power Mode
99h= Set Sleep Mode
9Ah= Vendor Unique
A0h= Send SCSI command to CD-ROM
C0h= Vendor Unique
C1h= Vendor Unique
C2h= Vendor Unique
C3h= Vendor Unique
C4h= Read Multiple
C5h= Write Multiple
C6h= Set Multiple Mode
C8h= Read DMA(with Retries)
C9h= Read DMA(without Retries)
CAh= Write DMA(with Retries)
CBh= Write DMA(without Retries)
DBh= Acknowledge media change
DCh= Boot - post-boot
DDh= Boot - pre-boot
DEh= Door lock
DFh= Door unlock
E0h= Standby Immediate
E1h= Idle Immediate
E2h= Standby
E3h= Idle
E4h= Read Sector Buffer
E5h= Check Power Mode
E6h= Set Sleep Mode
E8h= Write Buffer
E9h= Write same
ECh= Identify
EFh= Set Features
Fxh= Vendor Unique
Description o Output commands to the IDE drive.
o Some commands cannot be used depending on the drive. To find out which commands can be used, use the Identify command, etc.
Related INT 1Bh - Function D0h(IDE)
INT 1Bh - Function E0h(IDE)
INT 1Bh - Function F0h(IDE)
I/O 074Ch
Name Alternate Status Register,Digital Output Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ] Alternate Status Register
Explanation o The contents are the same as the Status Register of I/O 064Eh. However, the status register can be read without clearing the interrupt output.
[WRITE] Digital Output Register
bit 7~4: Unused (set to 0000b)
bit 3: Unused (set to 1)
bit 2: Reset
1=Reset IDE drive
0=normal
bit 1: IRQ Enable
1=Disable interrupts from IDE drives
0=Allow interrupts from IDE drives
bit 0: Unused (set to 0)
Explanation o Reset the IDE drive and set interrupts.
Related I/O 064Eh
I/O 074Eh
Name Digital Input Register
Undocumented
Target IDE I/F equipped machine
chip IDE drive
Function
[READ]
bit 7: unused
bit 6: Write Gate
1=normal
0=Drive is writing data onto media
bit 5～2: Head Select
* Inversion of Head Select of SDH register
bit 1,0: Drive Set1, Drive Set0
10b=Single mode/master selection
01b=Slave selection
Description o Read various statuses of IDE drive.
Related I/O 064Ch