Quantum ATL SuperLoader ATL, User Manual

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Chapter 3 Media Changer Commands
Read Buffer Command (3Ch)
124 Quantum ATL SuperLoader Software Interface Guide
The READ BUFFER command will return the same number of
bytes of data as received in the prior echo buffer mode WRITE
BUFFER command from the same initiator. If a prior Echo Buffer
mode WRITE BUFFER command was not successfully completed,
the Echo Buffer mode READ BUFFER command will terminate
with a CHECK CONDITION status, the sense key shall be set to
ILLEGAL REQUEST and the additional sense code to COMMAND
SEQUENCE ERROR. If the data in the Echo Buffer has been
overwritten by another initiator the drive will terminate the
command with a CHECK CONDITION status, the sense key will
be set to ABORTED COMMAND and the additional sense code to
ECHO BUFFER OVERWRITTEN.
Echo Buffer
Descriptor Mode
(1011b)
3
In this mode, a maximum of four bytes of READ BUFFER
descriptor information is returned. The device will return the
descriptor information for the Echo Buffer. The Buffer Offset field
is reserved in this mode. The allocation length should be set to four
or greater. The device shall transfer the lesser of the allocation
length or four bytes of READ BUFFER descriptor.
Figure 62 Echo Buffer
Descriptor
Bit
Byte
7 6 5 4 3 2 1 0
0
Reserved EBOS
1
Reserved
2
Reserved Buffer Capacity
3
Buffer Capacity