PAC Display/PAC Control TValue ERROR

Users of one of our systems reported the following error whilst using Display Runtime:

Referenced Type = Integer
Actual Type = Null

This popup appeared when they were using a small chart that accesses some int32 numerical tables. The interesting thing is that these charts have been used as is for years without this error ever appearing. Going back and checking all the related code there are no arraySize issues or typeAssignment issues and the tables are small (21 elements max). Having never encountered this on my development controllers, the only record I have of this happening is the screenshot they sent me of the popup above which I am guessing was generated by PAC Display (though PAC Control may have been open with the strategy in debug mode in the background so I guess it could be responsible).

Has anyone encountered this error? System is running V10.3 PAC Project and has otherwise been 100% bulletproof for thousands of operational hours.


Could it be that there was a communications issue and it did not grab the data for that point on a scan? Are you using SNAP PACs? If so, was there any error in the SNAP PAC log? Seems like it was upset because the memory location was empty. Sorry, I have never seen this one.

Hi Dobraka
Thanks. It is entirely possible that there was a scan error of some sort. Perhaps unrelated but some weeks earlier there had been some ethernet comms issues (some scratchpad read/writes were misbehaving between communicating controllers+I/O Units) and then I noticed the Analogue and High Density Scanner rate for one of the EB1 brains was at something ridiculous like 250ms and it was causing other issues like missing some ‘slowly’ changing IDC32 inputs. Since I posted this question I still have not been able to reproduce the error popup, but I have also ditched the EB1 brain on the rack in favour of using a PAC-R1 as just an I/O unit. Maybe this is why I can’t get the error again.
With any luck somebody who knows the inner workings of the the PAC Project environment might chime in, maybe…