Seagate ST1000VX000 ユーザーズマニュアル

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 interrupt. 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:

9-10

Obsolete.

11-12

Reserved for TLC.

13

IDLE IMMEDIATE command with IUNLOAD feature is supported.

14

Shall be set to 1.

15

Shall be cleared to 0.

0

Ultra DMA mode 0 is supported.

1

Ultra DMA mode 1 is supported.

2

Ultra DMA mode 2 is supported.

3

Ultra DMA mode 3 is supported.

4

Ultra DMA mode 4 is supported.

5

Ultra DMA mode 5 is supported.

6

Ultra DMA mode 6 is supported.

8

Ultra DMA mode 0 is currently active.

9

Ultra DMA mode 1 is currently active.

10

Ultra DMA mode 2 is currently active.

11

Ultra DMA mode 3 is currently active.

12

Ultra DMA mode 4 is currently active.

13

Ultra DMA mode 5 is currently active.

14

Ultra DMA mode 6 is currently active.

02

H

Enable write cache (default).

03

H

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

00

H

Set PIO mode to default (PIO mode 2).

01

H

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

08

H

PIO mode 0

09

H

PIO mode 1

0A

H

PIO mode 2 

0B

H

PIO mode 3

0C

H

PIO mode 4 (default)

20

H

Multiword DMA mode 0