VISA Equivalents for the GPIB-ENET's IBLOCK and IBUNLOCK FunctionsHardware: GPIB>>External Controllers/Convertors>>GPIB-ENET
Problem: I am using a GPIB-ENET box and making VISA function calls to it. Can I lock out other users from the ENET box automatically through VISA? I know that National Instruments has the iblock and ibunlock functions for GPIB, but I was wondering if there were VISA equivalents, and if so, could they be automatically invoked whenever a VISA session is started with a specific GPIB-ENET box? Solution: The answer is yes and no. VISA has locking with viLock and viUnlock. It works similarly to the NI-488 locking. However, in the old version (NI-VISA 2.01) VISA locks do not prevent NI-488 users from using it. VISA locks work fine, but only if all users of that GPIB-ENET box are using VISA. In the current version of VISA (NI-VISA 2.5) the VISA locks will internally call the NI-488 iblock function, so that you can mix and match NI-VISA and NI-488 applications and the locking will be consistent across both. For the final question, yes, you can lock upon opening a VISA session. Pass 1 (VI_EXCLUSIVE_LOCK) as the accessMode parameter. If viOpen returns successfully, that session has a lock and no other session can use that resource. (Although other VISA sessions can be opened without a lock, they cannot get a lock or do anything useful such as I/O.) Related Links: KnowledgeBase 1RHCPQPH: Locking and Unlocking a GPIB-ENET Attachments:
Report Date: 09/24/1999 Last Updated: 04/12/2002 Document ID: 1PNH90V8 |
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