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AT INTERFACE and ATA COMMANDS
WA31273A / WA32543A / WA33203A / WA32163A / WA31083A / WA32162A 6-33
This command is used by the host to establish the following parameters which affect the
execution of certain drive features as shown in Table 6-8.
Table 6-8.
Set Feature Register Definitions
Code
Description
02h
Enable Write Cache
03h
Set transfer mode based on value in Sector Count register
33h
Disable Retry
44h
11 bytes of ECC apply on Read Long/Write Long commands
55h
Disable read look-ahead feature
77h
Disable ECC
82h
Disable Write Cache
88h
Enable ECC
99h
Enable Retries
AAh
Enable read look-ahead feature
BBh
4 bytes of ECC apply on Read Long/Write Long commands
When the drive receives this command, it sets BSY, checks the contents of the Feature
register, clears BSY, and generates an interrupt. If the value in the Feature Register is not
supported or is invalid, the drive posts an Aborted Command error. Refer to section
6.6.3 for protocol.
A host can choose the transfer mechanism by Set Transfer Mode and specifying a value
in the Sector Count Register. The upper 5 bits define the type of transfer and the low
order 3 bits encode the mode value.
Block transfer (default)
00000
000
Single word DMA
Mode x
00010
0xx
Multi-word DMA
Mode 0
00100
000
6-4-18 Set Multiple Mode (C6h)
This command enables the drive to perform Read and Write Multiple operations and
establishes the block count for these commands. Refer to section 6.6.3 for protocol.
The Sector Count Register is loaded with the number of sectors per block. Drives