Interrupt 1Eh Vector of Diskette Controller Parameters(0:0078h) Dword address points to data base table that is used by BIOS.
Default location is at 0F000:0EFC7h. 11-byte table format:
bytes:
00h 4-bit step rate, 4-bit head unload time
01h 7-bit head load time, 1-bit Not DMA flag
02h 54.9254 ms counts - delay till motor off (37-38 typ)
03h sector size: (bytes/sector)
00h 128 bytes
01h 256 bytes
02h 512 bytes
03h 1024 bytes
04h last sector on track (sectors/cylinder - 8 or 9 typical)
05h gap between sectors on read/write (42 typical)
06h data length for DMA transfers (0FFh typical)
07h gap length between sectors for format (80 typical)
08h sector fill byte for format (0F6h typical)
09h head settle time (in milliseconds) (15 to 25 typical)
DOS 1.0 0
DOS 2.10 15
DOS 3.1 1
10h motor start time (in 1/8 second intervals) (2 to 4 typ.)
DOS 2.10 2
Interrupt 1Eh Vector of Diskette Controller Parameters
note 1) This vector is pointed to the ROM BIOS diskette tables on system
initialization
2) IBM recommends that if this table needs to be modified, it should be
copied into RAM and only the nescessary changes made.
3) The Step Rate, Head Unload Time, Head Load Time, and DMA flag are set
in the 8272, 8272A, or 82072 Floppy Disk Controller Chips using the
SPECIFY command (03h). These parameters are already formated for the
command as they appear in the Diskette Controller Parm table. Values
for the time parameters are dependant on the Data Rate Speed set in the
Data Rate Select Register and are documented in the Intel Product Line
Handbook for Peripherals. For the Step rate higher values result in
faster movement.
4) The Bytes/Sector, Sectors/Cylinder, Gap, and Fill Byte parameters are
used directly from the table by the FORMAT A TRACK command (0Dh or 4Dh)
of the Intel 8272, 8272A, and 82072 floppy disk controllers
5) Sample values for a DOS 3.3 machine are:
00: DF
01: 02
02: 25
03: 02
04: 12
05: 1B
06: FF
07: 54
08: F6
09: 01
10: 08