Chapter 5
S Mode Functions
© National Instruments Corp.
5-95
GPIB-SCSI-A User Manual
stat
(continued)
In general, the GPIB-SCSI-A updates the first three status
variables at the end of each programming message. It updates
the fourth status variable, count, after a
cmd
,
rd
,
brd
,
bwrt
,
or
wrt
function. Errors reported correspond to the previous
programming message. For example, if you call
wrt
and then
stat
, any errors returned to you correspond to errors in the
wrt
programming message, not
stat
.
The information transfer phases that the GPIB-SCSI-A drives
the SCSI through after selection are the Command, Data In,
Status, and Message In phases.
Mode indicates whether or not we want to enable or disable
continuous status reporting. When Mode is 1, the status
information is sent to the Initiator after every command except
for
inq
and
rqsns
.
The continuous status information is sent during the Message
In phase as an extended message. This message is sent just
before the Status byte is sent. The bytes of the extended
message consist of the following :
•
Byte 1:
01H : extended message indicator
•
Byte 2:
09H : extended message length
•
Byte 3:
FFH : extended message code
•
Bytes 4-11:
The eight bytes of status information as
defined above.
Note: Even when continuous status reporting is enabled, the
stat
command returns the status information during
the Data In phase, not the Message In phase.
See Also:
Appendix B, Status and Message Information, for additional
status information.
