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12.49.1 Write Cache (02h)
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 remain disabled. For current write cache function status, please refer
to Identify Device Information (Word 85 or 129) by Identify Device command.
12.49.2
Set Transfer Mode (03h)
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.
00000
001
PIO Default Transfer Mode
00000
000
PIO Default Transfer Mode
Disable IORDY
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)
12.49.3
Advanced Power Management (05h)
When the value in the Feature register is 05h (=Enable Advanced Power Management), the Sector Count Register
specifies the Advanced Power Management level.
FFh ---
Aborted
C0 – FEh ---
The deepest power saving mode is Idle mode
(the same as Disable Advanced Power Management)
80 – BFh ---
The deepest power saving mode is Low power Idle mode
01 – 7Fh ---
The deepest power saving mode is Low RPM Idle mode
00h ---
Aborted
The idle time to Low power idle mode and Low RPM idle mode vary according to the value in Sector Count register
as follows:
When Low power idle mode is the deepest power saving mode,
Y1=(x-80h) * 5+120 [sec] (120<= Y1<=435)
Y2=N/A(the device does not go to Low RPM idle mode)
When Low RPM idle mode is the deepest power saving mode and the value in Sector Count register is between
40h and 7Fh,
120<=Y1<=435 [sec] (default: 120 [sec])
Y2=(x-40h) * 60 + 600[sec] (600<=Y2<=4380)
When Low RPM idle mode is the deepest power saving mode and the value in Sector Count register is between 01h
and 3Fh,
120<=Y1<=435 [sec] (default: 120 [sec])
Y2=600 [sec]
Where x is the value in Sector Count register, y1 is the idle time to Low Power Idle mode, and y2 is the idle time to
Low RPM idle mode.
If Low power idle mode has already been enabled (i.e., y1 has been set) before Low RPM idle mode is enabled, y1 is
preserved. If Low power idle mode is disabled (i.e., y1 has not been set yet), y1 becomes 120[sec] when Low RPM
idle mode is enabled.
Enabled power saving mode and idle time (y1 and y2) are preserved until Advanced Power Management is disabled,
the deepest power saving mode becomes Idle mode, or new time is set. They are initialized with a hard/soft reset
unless Reverting to power on defaults is disabled and the device receives a soft reset.
280
Hard Disk Drive Specification