User's Guide

Chapter 3 Emulated DLT7000 SCSI Commands
Read (08h)
230 Quantum DX-Series Software Interface Guide
Table 179 READ
Command Descriptor
Block - Field
Descriptions
Field Name Description
SILI Suppress Incorrect Length Indicator. If the SILI bit is set to 1 and the Fixed bit is
set to 1, the target terminates the command with CHECK CONDITION status,
sense key set to ILLEGAL REQUEST, and additional sense code of INVALID
FIELD IN CDB.
If the SILI bit is 0 and the actual block length is different than the specified
transfer length, a CHECK CONDITION status is returned. Within the sense
data, the Incorrect Length Indicator (ILI) bit and Valid bit will be set to 1. The
sense key field specifies NO SENSE. The information bytes are set to the
difference (residue) between the requested transfer length and the actual block
length., or, in Fixed Block mode, the difference (residue) between the requested
number of blocks and the actual number of blocks read. No more than transfer
length blocks are transferred to the initiator and the tape is logically positioned
after the block (EOM side).
Fixed This bit specifies whether fixed-length or variable-length blocks are to be
transferred, and gives meaning to the Transfer Length field of the READ
command.
When set to 0, variable-block mode is requested. A single block is transferred
with the Transfer Length specifying the maximum number of bytes the initiator
has allocated for the returned data.
When the Fixed bit is set to 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, no data is transferred and the current position
on the logical unit does not change. This is not an error condition.
A successful READ with Fixed bit set to 1 transfers (current block length) x (# of
blocks x block size) bytes of data to the host. Upon termination of READ, the
medium is logically positioned after the last block of data transferred (EOM).
Note that a READ command in fixed mode with an odd number of blocks
returns a CHECK CONDITION: the DLT7000 tape drive does not support odd
block number transfers.