Seagate Medalist ST31082A, Product Manual

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Chapter 7 Command Set
Page 60 ST3636A/ST31082A/ST31276A
Set Features (Set Look Ahead Read)
Command Number: EF hex
Description: This command is used by the host to establish the following
parameters which affect the execution of certain drive features as shown below:
• 02 hex enables write cache.
• 82 hex disables write cache.
• AA hex enables Read Look Ahead.
• 55 hex disables Read Look Ahead.
• 03 Set Transfer Mode
Any other values in the Features (Write Precompensation) register will result
in the Error bit set in the Status Register and the ABRT (abort) bit set in the
Error Register. The default state on power up (Power On Reset) is determined
by the value of the Feature Word, which is factory set. The drive will retain the
settings through both soft and hard resets.
The Set Transfer Mode command set the current transfer mode according to the
content of the Sector Count Register. The valid Sector Count Register values
are shown in the table below:
Sector Count
Register
Transfer Mode
00 hex Set default PIO transfer mode
01 hex
Disable IOCHRDY
08 hex Enable Mode 0 PIO with IOCHRDY enabled
09 hex Enable Mode 1 PIO with IOCHRDY enabled
0A hex
Enable Mode 2 PIO with IOCHRDY enabled
0B hex Enable Mode 3 PIO with IOCHRDY enabled
0C hex Enable Mode 4 PIO with IOCHRDY enabled
20 hex
Enable Multiword DMA Mode 0
21 hex Enable Multiword DMA Mode 1
22 hex Enable Multiword DMA Mode 2
One transfer mode subcommand may be issued for each SET FEATURES
Command.