Western Digital T13/2132-D - Manual (Page 25)

June 23, 2010 T13/2132-D Revision 3
Working Draft Enhanced Disk Drive - 4 (EDD-4) 13
5 <8GB INT 13h Functions (Conventional Functions)
The Conventional INT 13h functions can address a maximum of 8.4GB of device space. Sector sizes shall be
exactly 512 bytes. The Conventional INT 13h functions pass all parameters in registers using the following
template (see table 6) unless otherwise specified:
Table 6 — Conventional Register Definitions
Register Description
AH INT 13h function number (Range is 00h through 3Fh)
AL Number of sectors to transfer
CH Low 8 bits of Cylinder
CL
Bit Description
5:0 Sector number. This value shall be >= 01h and <= 3Fh
7:6 High order 2 bits of the cylinder
DH Head Number
DL
Bit Description
6:0 Drive number
7 Set to 1 for Fixed media, clear to 0 for removable media
ES:BX This register contains the buffer pointer (i.e., the beginning address of the buffer in system memory).
Commands that move data from the device to memory shall use this pointer as the destination for
the data. Commands that move data from memory to the device shall use this pointer as the source
for the data to be transferred.