National Instruments NI-488.2 ESRQ (16), ETAB (20)

Appendix C Error Codes and Solutions
© National Instruments Corporation C-9 NI-488.2 User Manual
ESRQ (16)
ESRQ can only be returned by a device-level ibwait call with RQS set in
the mask. 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
ibsta 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.
ETAB (20)
ETAB occurs only during the FindLstn and FindRQS functions. ETAB
indicates that there was some problem with a table used by these functions:
• In the case of FindLstn, ETAB means that the given table did not
have enough room to hold all the addresses of the Listeners found.
• In the case of FindRQS, ETAB means that none of the devices in the
given table were requesting service.
Solutions
In the case of FindLstn, increase the size of result arrays. In the case of
FindRQS, check to see if other devices not used by your application are
asserting SRQ. Disconnect them from the GPIB if necessary.