INT 13 - DISK - READ SECTOR(S) INTO MEMORY
        AH = 02h
        AL = number of sectors to read (must be nonzero)
        CH = low eight bits of cylinder number
        CL = sector number (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 AH=01h)
        AL = number of sectors transferred
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
        AWARD AT BIOS extended to handle more than 1024 cylinders by placing
          bits 10 and 11 of the cylinder number into bits 6 and 7 of DH
SeeAlso: AH=0Ah