SCSI Commands
Page
117
TEST UNIT READY
The Test Unit Ready command provides a means to check that the drive is ready.
If the drive is able to accept a medium-access command without returning a Check
Condition status, then the Test Unit Ready command will result in Good status.
If the drive is unable to become operational or is in a state that requires action from
the host to make the drive ready, then the Test Unit Ready command will result in a
Check Condition status with a sense key of Not Ready.
This command does not access the medium or initiate a diagnostic routine.
Command Descriptor Block
Byte
Bits
7
6
5
4
3
2
1
0
0
Operation Code (00h)
1
Ignored LUN Reserved
2
Reserved
3
Reserved
4
Reserved
5
Control
Field Descriptions
Field
Bytes
Bits
Description
Operation
Code
0
The Operation Code for Test Unit Ready is 00h.
Ignored
Logical
Unit
1
5-7
The LUN field is residual from the SCSI-1 days and is ignored.
Reserved
All reserved bits must be 0.
Control
5
The control field must be 0.
Completion Status
Code
Message
Description
00h
Good
Status
•
The drive is ready to perform any appropriate medium access command.
•
The drive remains in any previously set mode.
•
The tape is not moved.
02h
Check
Condition
Use the Request Sense command to retrieve the sense data.
Code
Message
Description
02h
Not Ready
No cartridge is present; an immediate command
is in progress; or the eject button has been
pressed.
04h
Hardware Error
Parity error on the SCSI bus or drive hardware
failure.
05h
Illegal Request
The Command Descriptor Block is invalid.
06h
Unit Attention
The cartridge was changed or the drive was re-
set.
