Host Engineering Forum
General Category => Do-more CPUs and Do-more Designer Software => Topic started by: belias on November 21, 2024, 07:57:46 PM
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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.
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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.
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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.
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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.
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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.