AB ControlLogix V20
Today we’ve had some issues following the PLC program being reloaded while Ignition was running. The first thing I noticed was that it still said “Connecting…Program Mode” even once the PLC was back in Run Mode.
I disabled the Device and then immediately re-enabled it. The status then went to “Connected…Run Mode” however I noticed that numerous tag values seemed to be “stuck” and didn’t mirror what was in the PLC. I did a “Refresh Browse” which seemed to kick a lot of them into life but there is still the odd one that was wrong, e.g. a Boolean that was ON in Ignition but OFF in the PLC.
Using OPC Quick Client showed it was ON (incorrectly) and quality GOOD.
I tried changing the OPC Path temporarily to (try to) release the OPC Subscription on the tag but as soon as I changed it back again I saw the incorrect value again.
Obviously Ignition is caching some information - e.g. when an online edit is done in the PLC it logs a message about “Processor Edit Number” changing. Is there a way I can force it to forget everything about a PLC (i.e. clear a cache) and then refresh it from the device, so hopefully it’s all up to date?
I’d hoped disabling and re-enabling the device would have done something like that but it doesn’t appear to.
I can’t really (or don’t want to) restart Ignition as there are other PLCs it’s currently connected to and logging data from so I don’t want to affect them.