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READ Command (08h) SDLT 600 SCSI Interface Guide

4-154 January 2005 81-81200-02 REV A01

4.14.1 Filemark and End-of-Data Handling

If the drive reads a Filemark, it returns a CHECK CONDITION status. Within the Sense Data, the

Filemark and Valid bits are set to 1 and the Sense Key field is set to 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 medium

after the Filemark.

If the drive detects End of Data (EOD) during a READ, it returns CHECK CONDITION status. Within

the Sense Data, the Valid bit is set to 1 and the Sense Key field is set to BLANK CHECK. The

information fields contain the residue count. The Additional Sense Code Qualifier fields are set. Upon

termination, the drive physically positions the medium after the last block on tape.

If the SILI bit is set to 1:

• The drive reports CHECK CONDITION status for an incorrect length

condition only if the overlength condition exists and the Block Length field in

the mode parameter block descriptor is non-zero, or

• The drive does not report CHECK CONDITION status if the only error is the

underlength condition or if the only error is the overlength condition and the

Block Length field of the mode parameters block descriptor is set to 0.

Fixed Specifies whether the drive is to transfer fixed-length or variable-length blocks

and gives meaning to the Transfer Length field of the READ command.

When set to 0, requests variable-block mode. A single block is transferred with

the Transfer Length specifying the maximum number of bytes the initiator has

allocated for the returned data. When set to 1, requests fixed-block mode.

Transfer

Length

When set to 1, specifies the number of blocks to be transferred to the initiator.

This setting is valid only if the drive is currently operating in fixed-block mode.

When set to 0, no data is transferred and the current position on the drive does not

change. This is not an error condition.

A successful READ operation with the Fixed bit set to 1 transfers x byes of data,

where x = (current block length)

× (# of blocks) × (block size) bytes of data to the

initiator. Upon termination of the READ command, the drive logically positions

the medium after the last block of data transferred (EOM side).

Table 4-88. READ Command Descriptor Block — Field Descriptions (Continued)

Field

Name Description

1 2 ... 191 192 193 194 195 196 197 198 199 200 201 ... 293 294

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