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Chapter 4: SCSI Commands
4-118
July 2004
81-81276-01 Rev A01
4.25 WRITE (0Ah)
The WRITE command transfers one or more blocks from the host to the current logical position. When
in Buffered Mode (see
“MODE SELECT (15h/55h)” on page 4-44
), the tape drive reports a GOOD
status on WRITE commands as soon as this data block has transferred to the data buffer.
BC
Byte Compare. This bit selects a CRC/ECC verification or a byte-by-byte
compare.
When set to 0, the tape drive performs an internal CRC/ECC check of the data.
When set to 1, the tape drive rejects the command.
Fixed
This bit specifies 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, the host is requesting a Variable Block mode. The tape
drive transfers a single block with the Transfer Length specifying the maximum
number of bytes the initiator has allocated for the returned data.
When the Fixed bit is 1, the Transfer Length specifies the number of blocks to be
transferred to the initiator. This is valid only if the logical unit is currently
operating in Fixed Block mode.
When the Transfer Length is 0, the tape drive transfers no data and does not
change the current position on the logical unit.
A successful READ with the Fixed bit set to 1 transfers (current block
length) × (Transfer Length) bytes of data to the host. Upon termination of READ,
the media is logically positioned after the last block transferred (EOM side).
Verification Length
This field specifies how many blocks to verify.
Table 4-69.
VERIFY (13h) Command Descriptor Block — Field Descriptions
(Continued)
Field Name
Description
Summary of Contents for DLT1/VS80 SCSI
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