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3.2.3 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 and 4 bytes of ECC.
The acceptable values for the Features register are defined as follows:
00
H
Set PIO mode to default (PIO mode 2) and enable IORDY
01
H
Set PIO mode to default (PIO mode 2) and disable IORDY
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)
08
H
PIO mode 0
09
H
PIO mode 1
0A
H
PIO mode 2
(default)
0B
H
PIO mode 3
0C
H
PIO mode 4
10
H
Single-word DMA mode 0
11
H
Single-word DMA mode 1
12
H
Single-word DMA mode 2
20
H
Multiword DMA mode 0
21
H
Multiword DMA mode 1
22
H
Multiword DMA mode 2
44
H
Sixteen bytes of ECC apply on Read Long and Write Long
commands
55
H
Disable read look-ahead (read cache) feature
66
H
Disable reverting to power-on defaults
82
H
Disable write cache
AA
H
Enable read look-ahead (read cache) feature
(default)
BB
H
4 bytes of ECC apply on Read Long and Write Long
commands
(default)
CC
H
Enable reverting to power-on defaults
(default)
Note. At power-on, or after a hardware reset, the default values of the
features are as indicated above. A software reset also changes
the features to default values unless a 66
H
command has been
received.
28 Marathon 810 (ST9816AG) Product Manual, August 1995