Int 13 Fn 02  - Disk - Read Sector(s) Into Memory                          [B]

   AH = 02h
   AL = number of sectors to read (must be nonzero)
   CH = low eight bits of cylinder number
   CL = sector number 1-63 (bits 0-5)
        high two bits of cylinder (bits 6-7, hard disk only)
   DH = head number
   DL = drive number (bit 7 set for hard disk)
   ES:BX -> data buffer

Return: CF set on error
       if AH = 11h (corrected ECC error), AL = burst length
   CF clear if successful
   AH = status (see #0166)
   AL = number of sectors transferred (only valid if CF set for some
         BIOSes)

Notes: errors on a floppy may be due to the motor failing to spin up quickly
     enough; the read should be retried at least three times, resetting
     the disk with AH=00h between attempts
   most BIOSes support "multitrack" reads, where the value in AL
     exceeds the number of sectors remaining on the track, in which
     case any additional sectors are read beginning at sector 1 on
     the following head in the same cylinder; the MSDOS CONFIG.SYS command
     MULTITRACK (or the Novell DOS DEBLOCK=) can be used to force DOS to
     split disk accesses which would wrap across a track boundary into two
     separate calls
   the IBM AT BIOS and many other BIOSes use only the low four bits of
     DH (head number) since the WD-1003 controller which is the standard
     AT controller (and the controller that IDE emulates) only supports
     16 heads
   AWARD AT BIOS and AMI 386sx BIOS have been extended to handle more
     than 1024 cylinders by placing bits 10 and 11 of the cylinder number
     into bits 6 and 7 of DH
   under Windows95, a volume must be locked (see INT 21/AX=440Dh/CX=084Bh)
     in order to perform direct accesses such as INT 13h reads and writes
   all versions of MS-DOS (including v7 [Win95]) have a bug which prevents
     booting on hard disks with 256 heads, so many modern BIOSes provide
     mappings with at most 255 heads

See Also: AH=03h,AH=0Ah,AH=06h"V10DISK.SYS",AH=21h"PS/1",AH=42h"IBM"

See Also: INT 21/AX=440Dh/CX=084Bh,INT 4D/AH=02h