Alarm Message Transaction Group

I have two cnc machines running Fanuc 0i-md controllers. I have a transaction group setup to log alarm messages from the controllers. My main connection to the controllers is through Kepware. Kepware is able to read the alarm status on the controller, in other words, whether an alarm is present or not, 0 or 1. To get the actual alarm message, the only way was to go through a Fanuc OPC server which supports the alarm messages. Neither Kepware nor Ignition could run the function to retrieve the messages.

The Fanuc OPC tag is a string array size 3, having up to 3 simulataneous alarm messages at once. When the transaction group runs, sometimes I miss the messages and it just logs blank strings. Currently, I have the transaction group run on trigger on item: ALARM MESSAGES (string array), Active on value change, only execute once while trigger is active. 500 ms timer. I’ve also tried triggering on the alarm status tag from Kepware, I’ve tried 500 ms, 1 sec , 5 sec, and 3 sec timers. I still get missed messages when the group runs.

Any pointers, suggestions on how to fix this?

Try changing the OPC execution mode of the group (in the advanced properties) to ‘Read’ instead of ‘Subscribed’ - that will tell the group to do a (blocking) direct read of the values from the OPC item(s), rather than using the best effort last value brought in by the standard OPC subscription.

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Thanks, I’ll give it a go and see what happens