Quantum DLTtape DLT 7000, Product Manual

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SCSI Commands
5-168 Quantum DLT 7000 Tape System
5.25 WRITE COMMAND (0Ah)
The WRITE command transfers one or more blocks from the host to the current
logical position. When in Buffered Mode (the DLT tape drive default mode), the
tape drive reports GOOD status on WRITE commands as soon as this data
block has been transferred to the data buffer. Any check conditions will be
experienced as deferred errors. Refer to the MODE SELECT command
subsection for more information on Buffered Mode.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (0Ah)
1 Logical Unit Number Reserved Fixed
2 - 4
(MSB)
Transfer Length
(LSB)
5 Unused Reserved Flag Link
Figure 5–81 WRITE Command Descriptor Block - Data Format
Table 5–82 WRITE Command Data - Field Descriptions
Field Name Description
Fixed The fixed bit specifies both the meaning of the Transfer Length field and whether
fixed-length or variable-length blocks are to be transferred.
When the Fixed bit is 0, Variable-length block mode is selected. A single block is
transferred from the initiator and is written to the logical unit beginning at the
current logical tape position. Upon successful termination, the tape is logically
positioned after this block (on the EOM/P side). The Transfer Length specifies the
number of bytes that the drive handshakes out from the initiator as one block.