Quantum 10K II - Manual (Page 274)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–207
5.42 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.
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.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (1Bh)
1 Reserved Immed
2 - 3 Reserved
4 Power Conditions Reserved LoEj Start
5 Control
Figure 5–102 START STOP UNIT Command Descriptor Block — Data Format
Table 5–97 START STOP UNIT Command — Field Descriptions
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 successfully and is ready for media access commands.
LoEj Load Eject. This value must be zero, because the disk drive contains non-
removable medium.
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 rejected with CHECK CONDITION status and the proper sense
data.
Power Conditions The Power Conditions field is not supported.