Holding Outputs

Dear Community Members,

In the below configuration if both the PLCs are disconnected or the communication between both the PLCs and the bus coupler(X20BB80) is lost, can I hold the last known good values on the output modules?

Also when I disconnect both the network cables to the Bus Coupler (X20BB80) both the PLC reboots. Is there a way to avoid it?

Hello Asham,

Standard modules cannot hold the last known output once communication is lost but reACTION I/O modules can in blackout mode. Blackout mode allows for continued execution of the application in lower-level subsystems if other components fail. On the modules blackout mode is carried out if the network connection to the higher-level controller is interrupted and stopped when the network disturbance is corrected. If you want to learn more look at the help pages below :point_down::

Automation Help | reACTION I/O Modules
Automation Help | Blackout Mode

Both the PLCs may be rebooting because module supervised is on which it is by default. Module supervised makes the PLC go into service mode if the module is unplugged or not ok. This setting can be found in the bus controllers configuration. With this setting off the PLC should stay in run mode even if the bus controller is unplugged.