Copyright(C) 1994 Terumasa KODAKA , Takeshi KONO


■320KB FD BIOS

Overview of the 320KB floppy disk

The 320KB FD BIOS is a BIOS that accesses the FDD connected to the 320KB floppy disk interface.
The 320KB floppy disk interface is standard on the original PC-9801 E, F, and M.
The same is true for other models that support it. The processing routine exists in the main BIOS.

The 320KB FDD is originally an intelligent floppy disk drive for the PC-8001/PC-8801.

INT 1Bh - Function 00h,02h,07h,08h,09h,0Ah,0Bh,0Ch,0Fh(320KB FD)
Category         320KB FD BIOS
Name             No operation
Target           320KB BIOS
Input            AH=00h,02h,07h,08h,09h,0Ah,0Bh,0Ch,0Fh
                 AL=DA/UA(50-53h)
Output           AH=00h(CF=0)
Explanation    o Does nothing.
Related


INT 1Bh - Function 01h (320KB FD)
Class            320KB FD BIOS
Name             VERIFY
Target           320KB BIOS
Input            AH=01h
                 AL=DA/UA (50-53h)
                 BX=Data length (0001-1000h)
                 CL=Cylinder number (double-sided disk: 00-27h, single-sided disk: 00-22h)
                 DH=Head number (double-sided disk: 00-01h, single-sided disk: 00h)
                 DL=Sector number (01-10h)
Output           AH=00h (CF=0): Normal End
                    10h (CF=0): Write Protected
                    20h (CF=1): DMA Boundary
                    40h (CF=1): Equipment Check
                     80h (CF=1): Error
                    90h (CF=1): Time Out
Explanation    o Reads the specified sector and returns the return code. No transfer to memory is performed.
Related          INT 1Bh - Function 06h (320KB FD)


INT 1Bh - Function 03h (320KB FD)
Class            320KB FD BIOS
Name             INITIALIZE
Target           320KB BIOS
Input            AH=03h
                 AL bit 7-4=DA(5h)
                   bit 3-0=Single-sided/Double-sided mode
                   bit 3=UNIT #3
                   bit 2=UNIT #2
                   bit 1=UNIT #1
                   bit 0=UNIT #0
                     (1=Double-sided mode, 0=Single-sided mode)
Output           AH=00h (CF=0): Normal end
                    40h (CF=1): 320KB FD BIOS is not supported
Explanation    o Initializes the 320KB FD BIOS.
                 This must be executed before using other functions.
               u The technical data book states that no return code is returned, but AH=00h is used when the function is normally ended.
               u The '86 Technical Data Book has a different correspondence between bits 3-0 and unit numbers than the actual one.
Related          INT 1Bh - Function 0Eh(320KB FD)
                 0000:055Ch bit 7-4
                 0000:0560h
                 0000:0561h
                 0000:0562h


INT 1Bh - Function 04h(320KB FD)
Class            320KB FD BIOS
Name             SENSE
Target           320KB BIOS
Input            AH=04h
                 AL=DA/UA(50-53h)
Output           AH bit 7-4=0000b(CF=0): Normal End
                            0001b(CF=0): Write Protect
                            0100b(CF=1): Equipment Check
                    bit 3,2=Unused
                    bit 1=1: Double-sided device
                      0: Single-sided device
                    bit 0=1: Double-sided mode
                      0: Single-sided mode
Explanation    o Gets the status of the specified drive.
Related


INT 1Bh - Function 05h (320KB FD)
Class            320KB FD BIOS
Name             WRITE DATA
Target           320KB BIOS
Input            AH=05h
                 AL=DA/UA (50-53h)
                 BX=Data length (0001-1000h)
                 CL=Cylinder number (double-sided disk: 00-27h, single-sided disk: 00-22h)
                 DH=Head number (double-sided disk: 00-01h, single-sided disk: 00h)
                 DL=Sector number (01-10h)
                 ES:BP=Buffer address
Output           AH=00h (CF=0): Normal End
                    20h (CF=1): DMA Boundary
                    40h (CF=1): Equipment Check
                    80h (CF=1): Error
                    90h (CF=1): Time Out
Explanation    o Write data to the specified sector. Related


INT 1Bh - Function 06h (320KB FD)
Classification   320KB FD BIOS
Name             READ DATA
Target           320KB BIOS
Input            AH=06h
                 AL=DA/UA (50-53h)
                 BX=Data length (0001-1000h)
                 CL=Cylinder number (double-sided disk: 00-27h, single-sided disk: 00-22h)
                 DH=Head number (double-sided disk: 00-01h, single-sided disk: 00h)
                 DL=Sector number (01-10h)
                 ES:BP=Buffer address
Output           AH=00h (CF=0): Normal End
                    20h (CF=1): DMA Boundary
                    40h (CF=1): Equipment Check
                    80h (CF=1): Error
                    90h (CF=1): Time Out
Explanation    o Reads data from the specified sector.
Related          INT 1Bh - Function 01h (320KB FD)


INT 1Bh - Function 0Dh(320KB FD)
Category         320KB FD BIOS
Name             FORMAT DRIVE
Target           320KB BIOS
Input            AH=0Dh
                 AL=DA/UA(50-53h)
Output           AH=00h(CF=0): Normal End
                    20h(CF=1): DMA Boundary
                    40h(CF=1): Equipment Check
                    80h(CF=1): Error
                    90h(CF=1): Time Out
Description    o Formats the media of the specified drive.
Related


INT 1Bh - Function 0Eh (320KB FD)
Classification   320KB FD BIOS
Name             SET OPERATION MODE
Target           320KB BIOS
Input            AH=0Eh
                 AL bit 7-4=DA(5h)
                   bit 3-0=Single-sided/Double-sided mode
                   bit 3=UNIT #3
                   bit 2=UNIT #2
                   bit 1=UNIT #1
                   bit 0=UNIT #0
                     (1=Double-sided mode, 0=Single-sided mode)
Output           AH=00h (CF=0): Normal End
                    40h (CF=1): Equipment Check
Explanation    o Specifies single-sided/double-sided mode for each drive on the double-sided device.
               u The '86 edition technical data book has a different correspondence between bits 3-0 and unit numbers than the actual one.
Related          INT 1Bh - Function 03h (320KB FD)