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11.8.27 Power Control (Exh)
COMMAND CODE
1 1 1 0 X X X X
REGISTER
REGISTER SETTING NORMAL COMPLETION
DR drive no. no change
CY no change
HD no change
SN no change
SC shown below 00/FFH (for E5/98 command)
no change (for other command)
FT no change
Power Control is a group of commands which controls low power mode in the drive. The drive has three
types of power mode:
Idle, Stand-by and Sleep mode
At the completion of disk access, the drive automatically enters the idle mode.
There are two ways to shift to the stand-by mode ( to stop rotation of spindle motor ).
By a command from the host
By internal timer
The internal timer is set by Stand-by or Idle command. If the drive receives disk access command from the
host when it is in stand-by mode , the spindle starts rotating and the drive executes read/write operation.
After power on, the spindle starts rotating and enters the idle mode. During idle or stand-by, READY bit is
set and the drive is ready to receive a command.
To be specific , there are four different sub-commands defined by lower 4 bits of command as follows. The
drive is in the idle mode when it is in default condition after power- on.
11.8.27.1 Stand-by Immediate (E0/94)
SC=X (Don't care)
The drive enters the stand-by mode immediately by this command. If the drive is already in the stand-by
mode, it does no-operation and the stand-by timer doesn’t start .The drive issues an interrupt and reports
the host that the command has been completed before it virtually enters the stand-by mode .
11.8.27.2 Idle Immediate (E1/95)
SC=X
The drive enters the idle mode immediately by this command. If the drive is already in the idle mode, it
does no-operation. If stand-by timer is enabled, timer will start. After the drive enters the idle mode, the
drive issues interrupt to report the host that the command has been completed.