Modbus Registers Randomly Timing Out

Ignition
1

I am trying to set up a connection to a Modbus TCP/IP device via the Ignition driver. The Modbus connection itself is healthy and isn't timing out, and I am reading data on the tags accurately. However, random registers will timeout at random times and then come back in. No more than 5 registers seem to be timing out at a time and the data comes back in within a few seconds.

We are currently reading data through Kepware to a FactoryTalk application with no issues and, other than the random timeouts on Ignition, the tags are displaying correct data. We are also able to write to the holding registers, and the data is being transmitted to the FCU controller.

The Ignition log shows a Request failed: FailureType == TIMEOUT warning message for the tags that drop out, but no timeouts/disconnects on the Modbus connection itself.

If it helps, we created a tag group to poll these tags every 100ms (the same as our Kepware configuration), and our Modbus connection on ignition is set up to allow for up to 2000 registers per request for each register type as well as a maximum of 5 concurrent requests.

Again, the data is being read and written accurately, and the tag values match what we are seeing on Kepware and on the Modbus device itself.

Has anyone encountered anything similar and could maybe help guide me in the right direction? Thanks in advance (:

2

That means your target device is losing track of that request. A wireshark capture of the traffic while this is happening would confirm.

{Setting the limit to 2000 holding or input registers per request is useless. The Modbus protocol has a hard limit of 125. All of the default settings in the driver are the maximums permitted.}