Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
266
18.45
TEST UNIT READY (00)
Table 249 TEST UNIT READY (00)
Byte
Bit
7
6
5
4
3
2
1
0
0
Command Code = 00h
1
Reserved = 0
Reserved = 0
2-4
Reserved = 0
5
VU = 0
Reserved = 0
FLAG
LINK
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 commands during the Power On period.