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SCSI Commands

5-118 Quantum DLT 4000 Tape Drive

READ Command (08h) (continued)

Table 5–56 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).

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Quantum DLT 4000 Manual Página 218