Quantum LTO 4, Руководство пользователя

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SCSI Commands: 51BWRITE Page 217
3.39 WRITE
The WRITE command transfers one or more data blocks from the Initiator to the
drive. If the Transfer Length is zero, no data is transferred, and the current position
of the tape is not changed. This condition is not considered an error.
3.39.1 WRITE Command Descriptor Block
Byte Bits
7 6 5 4 3 2 1 0
0 Operation Code (0Ah)
1 Ignored LUN Reserved Fixed
2 (MSB)
3
4
Transfer Length
(LSB)
5 Control
3.39.1.1 WRITE Command Field Descriptions
Field Bytes Bits Description
Operation
Code 0 The Operation Code for WRITE is 0Ah.
Ignored
Logical
Unit 1 5-7 The LUN field is vestigial from the SCSI-1 standard and is ignored.
Fixed 1 0 0 = Variable block length. Transfer Length contains the number of
bytes to write.
1 = Fixed block length, as specified by the MODE SELECT Block
Descriptor. Transfer Length contains the number of blocks to
write.
Transfer
Length 2-4 This field specifies the number of bytes (Fixed = 0) or blocks (Fixed
= 1) to be written. A transfer length of 0 is valid and no data is
written.
Reserved All reserved bits must be 0.
Control 5 See SCSI Command Control Byte Format on page 25.
If the Fixed bit is clear, the initiator will transfer a single block of the length indicated
in Transfer Length.
If the Fixed bit is set, the initiator will transfer a sequence of blocks. The Transfer
Length field gives the number of blocks. The current fixed block length gives the
length of the blocks.
At Early Warning, the drive completes the current block transfer and terminates the
command with a Check Condition, EOM bit set, and Sense Key equal to 0.
Subsequent WRITE commands complete with a Check Condition and the EOM bit
set.
If writing the buffer to tape is unsuccessful because of EOM, a Volume Overflow is
reported. The Residual count field in the REQUEST SENSE data reports the amount
of data not transferred. Writing can continue in the Early Warning region until EOM