Seagate Technology 10002475-003, Product Description Manual

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Chapter 5 ATAPI Interface
Page 52 STT8000 ATAPI Minicartridge Drive
Test Unit Ready
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.
Write
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation code (0Ah)
1 Reserved 1 (Fixed)
1 Reserved
2 (MSB)
3 Transfer Length
4 (LSB)
5 Reserved
The Transfer Length specifies the number of fixed 512 byte blocks to be
transferred. A transfer length of 0 indicates that no data is to be transferred
but is used on some drives to put DSC into write buffer mode.
The DSC bit is reset (0) after this command is accepted and all data has been
transferred. This bit is set (1) when there are at least 52 empty blocks in the
buffer available for the next WRITE command. Issuing a WRITE command
when the DSC bit is reset (0) will keep the ATA bus busy (BSY=1) until buffer