Specifications

34 AMD Geode™ GeodeROM Functional Specification
Removable Media
32087C
5.2.3 Function 02h - Read Sectors
Description:
Reads a caller-specified number of sectors in the buffer specified by the ES:BX register pair.
Supports:
Fixed disk and floppy disk.
Passed:
Returns:
Special Instructions:
During a floppy diskette read, the caller ensures the read operation:
1) Does not cross a 64 KB DMA page boundary (e.g., 2000:0h, 3000:0h, etc.).
2) Does not extend past the end of a physical cylinder.
The IBM PC/AT technical reference manual specifies the head register as a 4-bit value; the upper four bits of DH are
undefined on this type of system. Newer systems allow for a head value of 0-0FFh, or a maximum of 255 heads. The
INT 13h functions in this type of system are capable of translating between physical (drive reported) and logical cylin-
der, head, sector geometries.
Related Functions:
INT 13h "Function 01h - Get Disk Subsystem Status" on page 33.
INT 13h "Function 03h - Write Sectors" on page 35.
Parameter Description
AH 02h
AL Sector count
CH Cylinder bits [7:0]
CL Bits [7:6] = Cylinder bits [9:8]
Bits [5:0] = Start sector (1-based)
DH Drive head
DL Drive number
ES:BX Far pointer to caller-supplied buffer
Parameter Description
CF 0 = Success
1 = Failure
AH Status code:
See AH in "Function 01h - Get Disk Subsystem Status" on page 33
AL Total number of sectors read