INT 13,1 - Disk Status

	AH = 01

	on return:
	AL = status:

	Status in AL

	   00  no error
	   01  bad command passed to driver
	   02  address mark not found or bad sector
	   03  diskette write protect error
	   04  sector not found
	   05  fixed disk reset failed
	   06  diskette changed or removed
	   07  bad fixed disk parameter table
	   08  DMA overrun
	   09  DMA access across 64k boundary
	   0A  bad fixed disk sector flag
	   0B  bad fixed disk cylinder
	   0C  unsupported track/invalid media
	   0D  invalid number of sectors on fixed disk format
	   0E  fixed disk controlled data address mark detected
	   0F  fixed disk DMA arbitration level out of range
	   10  ECC/CRC error on disk read
	   11  recoverable fixed disk data error, data fixed by ECC
	   20  controller error (NEC for floppies)
	   40  seek failure
	   80  time out, drive not ready
	   AA  fixed disk drive not ready
	   BB  fixed disk undefined error
	   CC  fixed disk write fault on selected drive
	   E0  fixed disk status error/Error reg = 0
	   FF  sense operation failed

	- codes represent controller status after last disk operation
	- returns the status byte located at 40:41 in the BIOS Data Area