MEM 0040h:0042h - DISK - FLOPPY/HARD DRIVE STATUS/COMMAND BYTES                 
Size:	7 BYTEs
SeeAlso: MEM 0040h:0041h

    42h BYTE	XTIBM PC XT: command byte to hard disk controller
		ATIBM PC AT: write precompensation cylinder number / 4
    43h	BYTE	XTIBM PC XT: bit 5 = drive number, bits 3-0=head number
		ATIBM PC AT: sector count
    44h BYTE	XTIBM PC XT: bits 6,7 = high bits of track, bits 5-0 = start sector-1
		ATIBM PC AT: starting sector
    45h BYTE	low byte of track number
    46h BYTE	XTIBM PC XT: sector count
		ATIBM PC AT: high bits of track number
    47h BYTE	XTIBM PC XT: controlbyte from HD parameters (step rate,...)
		ATIBM PC AT: 101DHHHH, D=drive number, HHHH=head number
		    bit 7 = ECC mode (1)
		    bit 6 = unknown (0)
		    bit 5 = 512 byte sectors (1)
		    bit 4 = drive number
		    bit 3-0 head number
    48h BYTE	XTIBM PC XT: INT 13h subfunction number
		ATIBM PC AT: command byte to hard disk controller
SeeAlso: CALL F000h:211Eh
                                                                                

MEM 0040h:0042h - DISK CONTROLLER STATUS REGISTER 0                             
Size:	BYTE
SeeAlso: MEM 0040h:0043h


Bitfields for diskette controller status register 0:
Bit(s)	Description	(Table M0015)
 7-6	interrupt code
	00 normal completion
	01 abnormal termination during execution
	10 invalid command
	11 abnormal termination: ready line on/diskette change
 5	requested seek complete
 4	drive fault
 3	drive not ready
 2	head state at time of interrupt
 1-0	selected drive (drives 2&3 on PCIBM PC,XTIBM PC XT only)
SeeAlso: #M0016