Echo Mode; Echo Buffer Descriptor Mode - Dell PowerVault TL2000 Reference Manual

Bit 7
Byte
0 - n

Echo Mode

In this mode, the library returns the same number of bytes of data as received in the prior Echo Mode
WRITE BUFFER command from the same host. If a prior Echo Mode WRITE BUFFER command did not
complete successfully the Echo Mode READ BUFFER command shall return Check Condition status. The
sense key shall be set to ILLEGAL REQUEST and the sense data shall be set to COMMAND SEQUENCE
ERROR. If the data in the Echo Buffer has been overwritten by another host the library shall return Check
Condition status. The sense key shall be set to ILLEGAL REQUEST and the sense data shall be set to
ECHO BUFFER OVERWRITTEN. The maximum length of the Echo Mode buffer is 256 bytes.
Bit 7
Byte
0 - n

Echo Buffer Descriptor Mode

In this mode, the media changer returns the descriptor information for the Echo Buffer. The Buffer Offset
field is reserved in this mode. The Buffer ID field is ignored in this mode. Next table specifies the Buffer
Descriptor which is returned on a READ BUFFER command in Echo Buffer Descriptor Mode.
Bit 7
Byte
0
1
2
3
Field descriptions:
EBOS:
The Echo Buffer Overwritten Support bit is set. The library shall return
ECHO_BUFFER_OVERWRITEN sense data when the buffer is overwritten by another initiator.
Buffer Capacity:
The Buffer Capacity field returns the maximum size of the Echo Buffer in bytes. The Echo Buffer
can store up to 256 bytes.
3-52
TL2000 and TL4000 SCSI Reference
6 5
(data defined by previous Data Mode WRITE BUFFER command)
6 5
(data defined by previous Echo Mode WRITE BUFFER command)
6 5
Reserved
Buffer Capacity
4 3
4 3
4 3
Reserved
Reserved
(MSB)
2 1
2 1
2 1
EBOS
(LSB)
0
0
0