National Instruments NI-488.2 Benutzerhandbuch

© National Instruments Corporation

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.

Check to see if other devices not used by your application are asserting 
SRQ. Disconnect them from the GPIB if necessary.

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.

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.