Codesys 3.5 Modbus I/O to Zero on PLC stop [SOLVED]

CODESYS
1

Hi all,

I’ve encountered a potential (big) issue when it comes to the Modbus TCP configuration.
Hopefully there is something I’m missing in the configurator.

When a PLC goes to stop, exception, lose communication with I/O-node (750-362) the IOs are kept on the I/O-node even though I’ve set the parameters to “Set to zero”.

Does anyone have any experience with this?
For anyone struggeling with the same - Either you have to write/ set register 0x1001 or 0x1003 and use “Standard Watchdog Type” or use “Alternative Watchdog type” and set it directly on the coupler/ I/O-node.

1 Like
2

Hello!
I think you have setup what the master should do with the data from the slave if the connection is lost. Should the master remember the old value or change the variable to 0?

But you have already found the solution. You also want to setup what the slave should do at communication is lost. I use the alternative watchdog. All you need to do is set the watchdog timeout time and activate the watchdog in coupler web based management. (not writing to modbus registers 0x1001 necesary) . (maybe a reboot in the end…)