June 23, 2010

T13/2132-D Revision 3

8.26 Set Hardware Configuration (FN 4Eh)

The purpose of this function is to allow non-hardware-specific software to configure host adapter and devices for optimal operation. ATA channels may have two devices attached, but this function operates on a single-device basis. This shall be accommodated by the value that is returned in AL. If the host adapter supports the requested sub-function on a device basis, AL shall be cleared to 00h. If the host adapter only supports the setting on an ATA channel basis, AL shall be set to 01h. Once this function has been invoked, all subsequent INT 13h device-access functions shall use the mode specified by this invocation. This means that if "DMA Maximum" is enabled, INT 13h FN 02h shall read from the device using DMA transfers. The DMA/PIO selections are mutually exclusive. When "DMA Maximum" is enabled, "PIO Maximum" shall be disabled. If the requested mode change is not supported this function shall return with CF = 1b and AH = 01h.

Entry

 

 

 

 

AH 4Eh

 

 

AL

Hardware configuration sub-function (see table 29)

 

DL BIOS device number

Exit

 

 

 

 

Carry Clear

Function completed without error

 

 

AH

Shall be cleared to zero

 

 

AL

00h if command was safe, 01h if other devices are affected

 

Carry Set

Function completed with an error

 

 

AH

Shall be set to the error code

 

 

Table 29 — Hardware Configuration Sub-Functions

 

 

 

 

AL

 

 

Description

0h

Enable prefetch

 

 

 

 

1h

Disable prefetch

 

 

 

2h

Set maximum PIO transfer mode.

 

 

 

3h

Set PIO mode 0.

 

 

 

4h

Return to default PIO transfer mode. Return the system to the PIO mode enabled by the BIOS setup

 

utility.

 

 

5h

Enable INT 13h DMA maximum mode. Set the maximum rate allowed by both the host adapter and the

 

device.

 

 

 

 

 

6h

Disable INT 13h DMA

 

Working Draft Enhanced Disk Drive - 4 (EDD-4)

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Western Digital T13/2132-D manual Set Hardware Configuration FN 4Eh, Hardware Configuration Sub-Functions