Quantum DLT 4000 Product Manual page 285

DLT4000 SCSI Interface
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. If the Fixed bit is set to
zero, Variable 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 (EOM/P side).
The Transfer Length specifies the number of bytes that the drive handshakes out from
the initiator.
If the Fixed bit is set to one, the Transfer Length field specifies the number of blocks
to be transferred to the host beginning at the current tape position. This form of
WRITE is valid only if the logical unit is currently operating in Fixed Block mode, in
other words, when it has been instructed to use fixed-length blocks with MODE
SELECT. The current block length is the block length defined in the MODE SELECT
command. Upon termination, the tape is logically positioned after these blocks.
Transfer Length
This field contains the length of the data transfer in bytes or blocks, depending on
whether Fixed or Variable block mode is selected.
If the Transfer Length is zero, no data is transferred and the current position on the
logical unit is not changed.
Exception Conditions
If EOT is detected while writing, the drive will finish writing any buffered data. The
command terminates with CHECK CONDITION status. Within the Sense data, the
EOM bit is set, the Sense Key field is set to NO SENSE, and the Additional Sense
Code and Additional Sense Code Qualifier fields are set to EOM/P detected. The drive
attempts to complete any subsequent writes, returning a CHECK CONDITION status
in each case.
If the drive encounters the physical EOM when attempting write, CHECK
CONDITION status is returned. Within the Sense data, the EOM and Valid bits are
set, and the Sense Key field is set to VOLUME OVERFLOW. The Information fields
contain the residue count and the Additional Sense Code and Additional Sense Code
Qualifier fields are set to EOM/P Detected. The tape is physically positioned at
EOM/P.
DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem 8-125