MRX Errors but Exception is 0

[belias]

I have an MRX instruction inside a stage program that will run fine for months, and then all of a sudden it begins to error.  It's not obvious what's causing the error, but restarting the PLC will correct it.

Tonight, I was able to troubleshoot while the error was happening.  I see the instruction stage running, and then it jumps to the error stage.  I have the exception response set to go to D24, however D24 always remains 0.  According to the help table, 0 isn't an option.

What am I missing?



Thanks.

[BobO]

Exception Response contains the Modbus exception code returned by the server, but the instruction is failing, so there can't be a response from the server. The relevant error in the case is the system error. You can view that from the Sys Info dialog.

[belias]

OK that makes sense, thanks.

I wish I had taken a screenshot of that page, but I'm fairly sure it showed an operation timeout at the MRX rung.  I'll check this closer next time the error happens.

Also, this time I didn't fully reboot the PLC.  I only ran the PLC --> Re-initialize PLC I/O and that fixed the problem.

[BobO]

OK that makes sense, thanks.

I wish I had taken a screenshot of that page, but I'm fairly sure it showed an operation timeout at the MRX rung.  I'll check this closer next time the error happens.

Also, this time I didn't fully reboot the PLC.  I only ran the PLC --> Re-initialize PLC I/O and that fixed the problem.

What firmware version are you running? While we have had our share of issues with the Modbus server, I'm unware of any client side issues. I would like to better understand what might be going on.

[belias]

Hi Bob,

FW is 2.10.2

If you let me know what to check next time, I'll make sure to do that prior to restarting.