Set Features Command - Seagate ST9750423AS Product Manual

4.3.2

Set 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 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:
Table 8 Set Features command values
02 Enable write cache (default).
H
03 Set transfer mode (based on value in Sector Count register).
H
Sector Count register values:
00 Set PIO mode to default (PIO mode 2).
H
01 Set PIO mode to default and disable IORDY (PIO mode 2).
H
08 PIO mode 0
H
09 PIO mode 1
H
0A PIO mode 2
H
0B PIO mode 3
H
0C PIO mode 4 (default)
H
20 Multiword DMA mode 0
H
21 Multiword DMA mode 1
H
22 Multiword DMA mode 2
H
40 Ultra DMA mode 0
H
41 Ultra DMA mode 1
H
42 Ultra DMA mode 2
H
43 Ultra DMA mode 3
H
44 Ultra DMA mode 4
H
45 Ultra DMA mode 5
H
46 Ultra DMA mode 6
H
55 Disable read look-ahead (read cache) feature.
H
82 Disable write cache
H
AA Enable read look-ahead (read cache) feature (default).
H
F1 Report full capacity available
H
Note. At power-on, or after a hardware or software reset, the default values of the features are as indicated above.
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