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5-144 Maxtor Atlas 10K V
5.40 START STOP UNIT Command (1Bh)
The START STOP UNIT command enables or disables the logical unit for media
access operations. This command gives the initiator remote control over drive spin-
up and spin-down. The data format and field descriptions are shown in Table 5-199
and Table 5-200 respectively.
A jumper (or backplane connection) is used to select the spin-up mode. When
configured for remote control of spin-up (Option 3), the drive requires a START
STOP UNIT Command to spin up. See Chapter 3 for jumper-programming
instructions for your specific hard disk drive.
Table 5-199 START STOP UNIT Command Descriptor Block-Data Format
Table 5-200 START STOP UNIT Command-Field Descriptions
Bit
Byte
765 4 3210
0 Operation Code (1Bh)
1 Reserved Immed
2 - 3 Reserved
4 Power Conditions Reserved LoEj Start
5 Control
Field Description
Immed
Immediate. When 1, the drive returns GOOD status immediately after validating the
Command Descriptor Block, but before the drive spins up.
When 0, the drive does not return GOOD status until after the drive has spun up success-
fully and is ready for media access commands.
LoEj
Load Eject. This value must be zero, because the disk drive contains non-removable me-
dium.
Start
When Start is 1, the unit spins up (if it is not currently spinning) and is left in a state where
subsequent media access commands can succeed.
When the value is 0, the drive spins down. Subsequent media access commands are re-
jected with CHECK CONDITION status and the proper sense data.
Power
Conditions
The Power Conditions field is not supported.