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Copyright 1991 David Jurgens |
INT 13,A - Read Long Sector (XT & newer)
AH = 0A
AL = number of sectors (1-121 dec.)
CH = track number (0-1023 dec., see below)
CL = sector number (1-17 dec., see below)
DH = head number (0-15 dec.)
DL = fixed drive number (80h=drive 0, 81h=drive 1)
ES:BX = address of buffer
on return:
AH = status (see INT 13,STATUS)
AL = number of sectors actually transferred
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
- many good programming references indicate this function is only
available on the AT, PS/2 and later systems, but all hard disk
systems since the XT have this function available
- reads regular data sectors (128-1024 bytes) with an additional
4 byte ECC code included
- a DMA boundary error will occur if the buffer at ES:BX crosses
a 64K segment boundary
- 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│4│3│2│1│0│ CX
│ │ │ │ │ │ │ │ │ │ └─┴─┴─┴─┴─┴──── sector number
│ │ │ │ │ │ │ │ └─┴──────────── high order 2 bits of track number
└─┴─┴─┴─┴─┴─┴─┴──────────── low order 8 bits of track number
- see INT 13,2
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| Esc or Alt-X to exit |
int 13,a |
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