DLT1/VS80 SCSI Interface Guide
81-81276-01 Rev A01
July 2004
4-87
4.12.1 Filemark and End-of-Data Handling
If the tape drive reads a Filemark, it returns a CHECK CONDITION status. Within the Sense data, the
Filemark and Valid bits are set and the Sense Key field is NO SENSE. The information fields contain
the residue count. The Additional Sense Code and Additional Sense Code Qualifier fields are set to
Filemark Detected. Upon termination, the drive logically positions the media after the Filemark (EOM
side).
If the tape drive detects EOD during the READ, the tape drive returns a CHECK CONDITION status.
Within the Sense data, the Valid bit is set and the Sense Key field is BLANK CHECK. The EOM bit
may be set if the tape drive determines that the medium is positioned past the PSEN marker. The
information fields contain the residue count. The Additional Sense Code and Additional Sense Code
Qualifier fields are set. Upon termination, the media is physically positioned before EOD and after the
last block on medium.
4.12.2 End-of-Medium/Partition Handling
The meaning of EOM is different for a read than for a write type of command. EOM is only reported
when the physical EOM/P is encountered. The tape drive returns a CHECK CONDITION status. The
EOM and Valid bits are set and the Sense Key is MEDIUM ERROR. The information fields contain
the residue count and the Additional Sense Code and Additional Sense Code Qualifier fields are EOM/
P Detected. The medium is physically positioned at EOM/P.
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).
Table 4-52.
READ (08h) Command Descriptor Block — Field Descriptions
(Continued)
Field Name
Description
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