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19.45 TEST UNIT READY (00)
Table 233: TEST UNIT READY (00)
Byte
7
0
1
2-4
5
VU = 0
The TEST UNIT READY command allows the Initiator to check if the drive is READY. The SCSI specification defines
READY as the condition where the device will accept a media-access command without returning Check Condition status.
The drive will first verify that the motor is spinning at the correct speed. If the spindle motor is not spinning at the correct
speed, Check Condition status is returned with sense key of Not Ready. If the motor is spinning at the correct speed, the drive
accepts normal media access commands.
The TEST UNIT READY command is not intended as a diagnostic. No self diagnostic is performed by the device as a result
of this command.
The TEST UNIT READY command has special significance for power sequencing using the UNIT START command with an
Immediate bit of one. In this mode the UNIT START command returns Task Complete status before the completion of motor
spin-up and expects the initiator to issue TEST UNIT READY commands to determine when the motor has reached the proper
speed.
Note:
The spindle automatically starts in automatic spin-up mode. The drive does not execute any commands other than
TEST UNIT READY, INQUIRY, or REQUEST SENSE command until the Power On sequence is complete. The drive will
return Check Condition status with Not Ready sense key and In Process of Becoming Ready sense code for all other com-
mands during the Power On period.
6
5
Reserved = 0
Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
Bit
4
3
2
Command Code = 00h
Reserved = 0
Reserved = 0
Reserved = 0
272
1
0
FLAG
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