INT 13,2 - Read Disk Sectors

AH = 02

AL = number of sectors to read (1-128 dec.)

CH = track/cylinder number (0-1023 dec., see below)

CL = sector number (1-17 dec.)

DH = head number (0-15 dec.)

DL = drive number (0=A:, 1=2nd floppy, 80h=drive 0, 81h=drive 1)

ES:BX = pointer to buffer

on return:

AH = status (see ~INT 13,STATUS~)

AL = number of sectors read

CF = 0 if successful

= 1 if error

- 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):

¦F¦E¦D¦C¦B¦A¦9¦8¦7¦6¦5-0¦ CX

¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ +----- sector number

¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ +--------- high order 2 bits of track/cylinder

+------------------------ low order 8 bits of track/cyl number

- see ~INT 13,A~