INT 0x13 - 0x02 - Read Disk Sectors

Request/Call:

reg	value	descr
AH	0x02
AL	var	number of sectors to read (1-128 dec.)
CH	var	track/cylinder number (0-1023 dec., see below)
CL	var	sector number (1-17 dec.)
DH	var	head number (0-15 dec.)
DL	var	drive number (0=A:, 1=2nd floppy, 80h=drive 0, 81h=drive 1)
ES:BX	var	pointer to buffer

BIOS disk reads should be retried at least three times and the controller should be reset upon error detection
be sure ES:BX does not cross a 64K segment boundary or a DMA boundary error will occur
many programming references list only floppy disk register values
only the disk number is checked for validity
the parameters in CX change depending on the number of cylinders; the track/cylinder number is a 10 bit value taken from the 2 high order bits of CL and the 8 bits in CH (low order 8 bits of track):

bit	descr
0-5	sector number
6-7	high order 2 bits of track/cylinder
8-15	low order 8 bits of track/cyl number