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Command Specifications
4.1.8 REZERO UNIT (01)
Bit
Byte
0
1
2
3
4
5
This command moves the read/write heads of the disk drive to the initial position
(physical cylinder 0 / physical track 0). A data block with the physical block
address of zero exists at the initial position. Initialization of the disk drive's
positioning control system and automatic adjustment are also performed by this
command.
4.1.9 START/STOP UNIT (1B)
Bit
Byte
0
1
2
3
4
5
This command controls the power condition of the disk drive. For the power
condition, see Chapter 2, "Power Condition."
The control of the power condition is performed with the Start bit in bit 0 of the
CDB byte 4.
Issuing this command with the Start bit set to "0" transits from the power
condition state to the Stopped state. Meanwhile, setting the Start bit to "1"
transforms the power condition state from the Stopped state to the Active_Wait
state. Setting the Start bit to "1" does not transform the power condition state
when it is in a state other than the Stopped state.
4-84
7
6
5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
7
6
5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
3
2
X'01'
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
3
2
X'1B'
0
0
0
0
0
0
0
0
0
0
0
0
LoEj
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
0
0
Immed
0
0
0
0
Start
0
0
C141-C012
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