Bios Command Return Codes - Adaptec AHA-1740A Technical Reference Manual

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system processor is in real mode. Because this is the case at system boot time and un-
der normal DOS operation, simple segment arithmetic is normally used to convert
ES:BX to a physical address usable by the AHA-1740A/1742A:
Physical address = (Segment * 16) + Offset
The 386 processor, however has given rise to a large number of software products
which use the 386 memory management feature to provide virtual 8086 operation.
The address passed in ES:BX still appears valid to the BIOS, but the processor is not
in fact in real mode, and normal segment arithmetic will not yield the correct physi-
cal location of the data buffer. This issue has been addressed by IBM
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Microsoft in a specification known as Virtual DMA Services (VDS). This specifica-
tion provides a method to the ROM BIOS for determining the physical location of a
buffer given the selector:offset as well as its layout (it may not be contiguous). The
AHA-1740A/1742A BIOS will fully support the VDS specification so that 386 memory
management programs will be able to run without a driver as long as they are VDS
compliant. In ISA Standard Mode, however, VDS will not be supported and a driver
will be necessary to support VDS.

BIOS Command Return Codes

Any Int 13h request, upon completion, returns control to the requestor with a return
code set in the carry flag and a status code placed in AH. The carry flag is set as
follows:
CF=1
CF=0
Status code definitions returned in register AH, as well as the mapping from SCSI er-
ror conditions, are provided in the following table:
AH (Hex)
00
01
02
03
04
10
7-6
Error or unusual condition. Status is nonzero.
Command completed normally. Status is zero.
Definition
No Error: Operation completed successfully
Invalid Function Request: The Int 13h function code provided was not
valid or the drive number was out of range.
Unable to Read Address Mark: One of the following additional sense
codes (SCSI ASC) was presented in the sense information returned by the
target:
12h - No AM Found on Data Field
21h - Illegal Logical Block Address
Write Protect Error: Returned SCSI ASC:
27h - Data Protect
Read Error: Returned SCSI ASC:
14h - No Record Found
16h - Data Sync Error
Uncorrectable ECC Error: Returned SCSI ASC:
10h - ID ECC Error
11h - Unrecovered Read Error
AHA-1740A/1742A/1744
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