User's Guide

Chapter 2 Media Changer Commands
Read Buffer Command (3Ch)
Quantum SuperLoader 3 Software Interface Guide 98
Figure 56 Read Buffer
Descriptor
Read Data from Echo
Buffer (1010b) 2
In this mode the device transfers data to the application client from the
Echo Buffer. The Echo Buffer will transfer the same data as when the
WRITE BUFFER command with the mode field set to Echo Buffer was
issued. The
Buffer ID and Buffer Offset fields are ignored in this mode.
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) 2
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.
Bit
Byte76543210
0
Offset Boundaries (0h)
1 - 3
(MSB)
Buffer Capacity
(LSB)