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Chapter 8 SCSI Commands
The Buffer Capacity field contains the number of valid bytes of the autoloader
internal buffer. This value is not affected by the Allocation Length set in the
CDB or by the number of bytes actually written using the WRITE BUFFER
command. After the Read Buffer header, the autoloader transfers data from the
its data buffer.
When the number of bytes of transferred data added to the header reaches the
Allocation Length or when transfer of the valid header and Buffer Data
specified for transfer by the host is complete, the autoloader ends the DATA IN
phase.
8.11.2. Data mode (0010b)
In the Data mode, buffer data in the autoloader is transferred during the DATA
IN phase.
The Buffer Offset field indicates a data offset in the data buffer specified for
transfer. The host sets the Offset value following the Boundary request specified
by the autoloader. If this value is other than a supported Buffer Offset value, the
autoloader terminates the command with a CHECK CONDITION status. The
sense key is ILLEGAL REQUEST and ASC/ASCQ is ILLEGAL FIELD IN
CDB.
8.11.3. Read Data from echo buffer (1010b)
In this mode, data is transferred from the Echo Buffer to the host. Writing data
to the Echo Buffer is done by setting the Echo buffer and issuing a WRITE
BUFFER command. The Buffer ID and Buffer Offset are ignored.
This command returns values until it reaches the number of bytes of data
received by the WRITE BUFFER command issued previously by the host in
Echo Buffer mode. If the Allocation Length is insufficient to return the amount
of data received, the possible amount of data is returned, but this is not treated
as an error. If a WRITE BUFFER command issued in Echo Buffer mode fails,
a READ BUFFER command is issued in Echo Buffer mode, a CHECK
CONDITION is returned, the Sense Key is ILLEGAL REQUEST, and ASC/
ASCQ is COMMAND SEQUENCE ERROR. If the Echo Buffer data is
overwritten by another host, the READ BUFFER command in Echo Buffer
mode returns a CHECK CONDITION, the Sense Key is ABORTED
COMMAND, and ASC/ASCQ is ECHO BUFFER OVERWRITTEN.
