243
Western Digital Hard Disk Drive OEM Specification
11.46.1
Set Transfer Mode
When Feature register is 03h (=Set Transfer Mode), the Sector Count Register specifies the transfer mechanism.
The upper 5 bits define the type of transfer and the low order 3 bits encode the mode value.
PIO Default Transfer Mode
00000
000
PIO Default Transfer Mode
Disable IORDY
00000
001
PIO Flow Control Transfer Mode x
00001
nnn
(nnn=000,001,010,011,100)
Multiword DMA mode x
00100
nnn
(nnn=000,001,010)
Ultra DMA mode x
01000
nnn
(nnn=000,001,010,011,100,101,110)
11.46.2
Write Cache
If the number of auto reassigned sector reaches the device’s reassignment capacity, the write cache function will be
automatically disabled. Although the device still accepts the Set Features command with Feature register = 02h
without error, but the write cache function will remains disabled. For current write cache function status, please refer
to Identify Device Information (word 85 or 129) by Identify Device c ommand.
11.46.3
Serial ATA Feature
When the Feature register is set to 10h or 90h, the value set to the Sector Count register specifies the specific Serial
ATA feature to enable or disable.
Sector Count Value Description
01h
Non-zero buffer offset in DMA Setup FIS
02h
DMA Setup FIS Auto-Activate optimization
03h
Device-initiated interface power state transitions
04h
Guaranteed In-Order Data Delivery
06h
Software Settings Preservation
