iX and Modbus slave

[robkwan]

QTerm-A12 with the latest iX.

The A12 connects to an embedded controller with Modbus serial to exchange data. The A12 is the slave; the iX Modbus driver is Modbus Slave 4.16.02. The embedded controller is the master. A holding register is incremented at fixed rate by the master. The A12 checks this heartbeat tag every second, if the heartbeat did not change after 5 consecutive checks, the datalink alarm is triggered and displayed on the Alarm Viewer.

If the system is run long enough, say overnight, we would see the datalink alarm. Log records from the embedded controller indicates the A12 failed to reply. The SystemTagCPULoad is typical at 20-35%. We added a few CPU load counter tags; the 95% tag recorded a count of 3-4 overnight.

We assigned tags to all 5 pollgroups with 500, 750, 1000, 1500, 2000ms to reduce the update rate. We implemented hints in "optimizing iX application.pdf"

What causes the A12 to spike beyond 95% CPU load at idle?

We are not sure if the CPU load spike caused the Modbus comm error since it doesn't happen often. There are 713 tags mapped to the ModBus registers. Is this within the A12's capacity?

What do the Timeout and Retries settings in the Modbus Slave Setting dialog do for the slave? The A12 is the Slave, it only replies.

What else to try?

[Jae V]

Hello,
We understand that this is a very old post. Unfortunately they should not spike like that. We would need to drive into your project a little more or put the project on a test bench so we could monitor that behavior to help troubleshoot more. If there is anyone who is still experiencing this or similar issues and require assistance, please visit us at https://www.beijerelectronics.us/en-US/ ... ___support or give us call at 801.708.6690. Thank you.