Quantum LTO 4, Руководство пользователя

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SCSI Commands: 31BREAD BUFFER Page 143
Byte Bits
7 6 5 4 3 2 1 0
0 Offset Boundary
1 (MSB)
2
3
Buffer Capacity
(LSB)
3.19.3.1 READ BUFFER Descriptor Field Descriptions
Field Bytes Bits Description
Offset Boundary 0 Always 0h, indicating byte boundaries
Buffer Capacity 1-3 The capacity of the drive’s data buffer.
3.19.4 Echo Buffer Descriptor
If the Mode field is set to 0Bh, then the data returned is a 4 byte Echo Buffer
Descriptor. The following table shows the fields in the Echo Buffer Descriptor.
Byte Bits
7 6 5 4 3 2 1 0
0 Reserved EBOS
1 Reserved
2 Reserved (MSB)
3 Buffer Capacity (LSB)
3.19.4.1 Echo Buffer Field Descriptions
Field Bytes Bits Description
EBOS 0 0 Echo Buffer Overwrite Supported, always 1 indicating that the
drive returns the ECHO BUFFER OVERWRITTEN additional
sense code if the data in the echo buffer was written by a
different IT nexus.
Reserved 0 1-7 All bits are 0
Reserved 1 All bits are 0
Reserved 2 4-7 All bits are 0
Buffer Capacity 2-3 The capacity of the drive’s echo buffer.
3.19.5 Echo Buffer
The READ BUFFER command for the echo buffer shall return data from the most
recent WRITE BUFFER command for echo buffer on the same IT nexus. If no
WRITE BUFFER command for echo buffer preceded the READ BUFFER, then the
command will terminate with CHECK CONDITION status, with the sense key set to
ILLEGAL REQUEST, and additional sense code set to COMMAND SEQUENCE
ERROR. IF the data in the echo buffer has been overwritten by another IT nexus,
then the READ BUFFER command shall be terminated with CHECK CONDITION
status, with the sense key set to ABORTED COMMAND, and the additional sense
code set to ECHO BUFFER OVERWRITTEN.