Seagate STT8000A - Manual (Page 67)

ATAPI Interface Chapter 5
STT8000A Product Manual Page 59
Test Unit Ready command
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation code (00h)
1 Reserved
2 Reserved
3 Reserved
4 Reserved
5 Reserved
This command can be used to determine the readiness of the device to accept a
media access command. It’s purpose is to indicate the cartridge state: no cartridge
(or drive fault), cartridge becoming ready, or cartridge/drive ready.
If the drive is busy with a previous command (DSC reset), the drive will wait for the
previous operation to complete before releasing the ATA bus. On some other ATAPI
tape drives, Test Unit Ready does not wait for DSC set before completing, and if an
application needs to “wait” for an command done via the ATAPI interface, Read
Position should be used instead.