4.1.3Set Features command

This command controls the implementation of various features that the drive supports. When the drive receives this command, it sets BSY, checks the contents of the Features register, clears BSY and generates an inter- rupt. If the value in the register does not represent a feature that the drive supports, the command is aborted. Power-on default has the read look-ahead and write caching features enabled. The acceptable values for the Features register are defined as follows:

Table 8:

 

Features register values

 

 

 

02H

 

Enable write cache (default).

 

 

 

03H

 

Set transfer mode (based on value in Sector Count register).

 

 

Sector Count register values

 

 

 

 

 

 

 

00H

 

Set PIO mode to default (PIO mode 2).

 

 

 

 

 

 

 

01H

 

Set PIO mode to default and disable IORDY (PIO mode 2).

 

 

 

 

 

 

 

08H

 

PIO mode 0

 

 

 

 

 

 

 

09H

 

PIO mode 1

 

 

 

 

 

 

 

0AH

 

PIO mode 2

 

 

 

 

 

 

 

0BH

 

PIO mode 3

 

 

 

 

 

 

 

0CH

 

PIO mode 4 (default)

 

 

 

 

 

 

 

20H

 

Multiword DMA mode 0

 

 

 

 

 

 

 

21H

 

Multiword DMA mode 1

 

 

 

 

 

 

 

22H

 

Multiword DMA mode 2

 

 

 

 

 

 

 

40H

 

Ultra DMA mode 0

 

 

 

 

 

 

 

41H

 

Ultra DMA mode 1

 

 

 

 

 

 

 

42H

 

Ultra DMA mode 2

 

 

 

 

 

 

 

43H

 

Ultra DMA mode 3

 

 

 

 

 

 

 

44H

 

Ultra DMA mode 4

 

 

 

 

 

 

 

45H

 

Ultra DMA mode 5

 

 

 

 

05H

 

Enable advanced power management

 

 

 

55H

 

Disable read look-ahead (read cache) feature.

 

 

 

82H

 

Disable write cache.

 

 

 

AAH

 

Enable read look-ahead (read cache) feature (default).

 

 

 

F1H

 

Report full capacity available

 

 

 

 

 

Note. At power-on, or after a hardware or software reset, the default values of the features are as indi- cated above.

Momentus 42 Product Manual, Rev. A

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Seagate ST92014A, ST94019A, ST93015A manual Set Features command, Features register values