Test Unit Ready (00) - IBM Ultrastar 36LZX Specifications

8.38 TEST UNIT READY (00)

Byte
7 6
0
1 Reserved = 0
2
3 Reserved = 0
4
5 VU = 0
Figure 156. TEST UNIT READY (00)
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 START
UNIT command with an Immediate bit of one. In this mode the START UNIT command returns
COMMAND 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 com-
mands 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 commands during the Power On period.
Bit
5 4 3
Command Code = 00h
Reserved = 0
Reserved = 0
Ultrastar 36LZX hard disk drive specifications
2 1 0
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