Specifications

Byte Description
44
H
Use maximum length of ECC (> 4 bytes) on read long/write long
commands (the maximum ECC length varies among drives).
54
H
Set cache segments to Sector Count register value
55
H
Disable read look-ahead feature
66
H
Use current settings as default (until hard reset or power off)
77
H
Disable ECC
81
H
Disable 8-bit data transfers ( factory default )
82
H
Disable write cache (see product manual for default settings)
88
H
Enable ECC ( factory default )
99
H
Enable retries ( factory default )
AA
H
Enable read look-ahead feature ( factory default )
AB
H
Set maximum prefetch using value in Sector Count register
(see product manual for default settings)
BB
H
4 bytes of ECC apply on read long/write long commands
(
factory default )
CC
H
Enable reverting to power-on defaults (see product manual for
default settings)
At power-on, or after a hard reset, the feature selections are restored to
the factory default values. If 66
H
has been set, a software reset will not
change the feature selections (this can be canceled by setting CC
H
). If
66
H
has not been set, a soft reset will return the settings to the factory
defaults.
A host can choose the DMA transfer mechanism using Set DMA Transfer
mode and by specifying a value in the Sector Count register. The upper
5 bits define the type of DMA transfer and the low order 3 bits encode
the mode value.
Transfer mechanism Upper 5 bits Lower 3 bits
Block transfer (default) 00000 000
Single word DMA mode
x
(only valid if DMA supported)
00010 0
xx
Multiword DMA mode 0
(only valid if DMA supported)
00100 000
ATA Interface Reference Manual, Rev. C 51