Appendix B
Error Codes and Solutions
© National Instruments Corp.
B-7
NI-488.2M UM for Windows NT
Solutions
•
Verify that the instrument is operating correctly.
•
Check for loose or faulty cabling or several powered-off instruments on the GPIB.
•
If the timeout period is too short for the driver to send command bytes, increase the
timeout period.
ESTB (15)
ESTB is reported only by the
ibrsp
function. ESTB indicates that one or more serial
poll status bytes received from automatic serial polls have been discarded because of a
lack of storage space. Several older status bytes are available; however, the oldest is
being returned by the
ibrsp
call.
Solutions
•
Call
ibrsp
more frequently to empty the queue.
•
Disable autopolling with the
ibconfig
function or the
ibconf
utility.
ESRQ (16)
ESRQ occurs only during the
ibwait
function or the
WaitSRQ
routine. ESRQ
indicates that a wait for RQS is not possible because the GPIB SRQ line is stuck on. This
situation can be caused by the following events:
•
Usually, a device unknown to the software is asserting SRQ. Because the software
does not know of this device, it can never serial poll the device and unassert SRQ.
•
A GPIB bus tester or similar equipment might be forcing the SRQ line to be asserted.
•
A cable problem might exist involving the SRQ line.
Although the occurrence of ESRQ warns you of a definite GPIB problem, it does not
affect GPIB operations, except that you cannot depend on the RQS bit while the
condition lasts.
Solutions
Check to see if other devices not used by your application are asserting SRQ. Disconnect
them from the GPIB if necessary.