Read 08H - Sony DDS-4 Product Description Manual

6. COMMAND SPECIFICATION

6. 10 READ 08h

Bit 7
Byte
0
1 Logical Unit Number
2 (MSB)
3
4
5 Unused (00b)
READ transfers one or more data blocks to the initiator starting with the next block on the drive.
Fixed: This bit specifies 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 requested. A single block is transferred with the Transfer
Length specifying the maximum number of bytes the Host has allocated for the returned data.
If the Fixed bit is set to one, the Transfer Length specifies the number of blocks to be transferred to the Host. This
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 command. If the Fixed bit is set and the drive is in
Variable Block mode, the READ is rejected with a CHECK CONDITION status and an ILLEGAL REQUEST
sense key set.
When the Transfer Length is zero, no data will be transferred and the current position on the logical unit will not
be changed.
A successful READ command with the Fixed bit set transfers (current Block Length) X (Transfer Length) bytes
of data to the Host. Upon termination of the READ command, the media will be logically positioned after the last
block transferred (EOM side).
SILI: A Suppress Incorrect Length Indicator bit of one indicates that the device will not return CHECK CONDITION
status if the only error is that the Transfer Length is not equal to the actual Block Length recorded on the media.
Note, however, that if the SILI bit is one and the Fixed bit is zero, then the device WILL report CHECK CONDI-
TION if the requested Transfer Length is less than the actual record size recorded on the medium (overlength
condition) AND the device is configured to be in Fixed Block mode (i.e. the Block Length field in the MODE
SELECT/SENSE block descriptor is non-zero).
If the SILI bit is one and the Fixed bit is one, the drive will terminate the command with a CHECK CONDITION
status with the sense key set to ILLEGAL REQUEST and the additional sense code to ILLEGAL FIELD IN
CDB.
If the SILI bit is not set and the actual Block Length is different from 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 one, the Sense Key field is set to NO SENSE and the Information Bytes are to set 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 bytes are transferred to the initiator and the tape is logically positioned after the last block transferred
(EOM side).
6 5 4
Operation Code (08h)
Transfer Length
3 2
Reserved
Reserved
SONY SDT-10000/SDT-11000 DDS Tape Drive
READ
1 0
SILI Fixed
(LSB)
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