Quantum Instruments DLT 7000 - Manual (Page 269)

SCSI Commands
Quantum DLT 7000 Tape System 5-165
5.23 TEST UNIT READY COMMAND (00h)
The TEST UNIT READY command checks the tape drive to ensure that the unit
is ready for commands involving tape movement. If the drive has a tape loaded,
the command returns a GOOD status. Otherwise, CHECK CONDITION is
reported.
Due to power cycle, code update, and tape loaded conditions, it is possible to get
multiple check conditions on a TEST UNIT READY command.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (00h)
1 Logical Unit Number Reserved
2 - 4 Reserved
5 Unused Reserved Flag Link
Figure 5–79 TEST UNIT READY Command Descriptor Block - Data Format