Inhibit Module in Control logix

[ChongKY1 1]

hello, all, is there any method to inhibit a module in control logic when the plc is switch to Program Mode ? I have tested the GSV, get the program mode status and then inhibit the module in control logic, but it's sometimes work and sometimes not work (I guess is due to the last scan didn't scan that rung), so anyone know how to inhibit a module when the plc is switch to program mode ? FYI, I'm doing redundancy plc, one plc switch to program mode, another take over as primary, and have to inhibit the control net in the plc which switch to program mode.

[jimdi4 2]

Why do you need to inhibit the Controlnet module when your in program mode?

[ChongKY1 1]

if i didn't inhibit the controlnet, the plc processor which turn to program mode one will still holding my MCM card, the others CPU which is now as Primary cannot take over it. unless the plc which turn to program mode I change back to run mode then only it will release the holding for MCM card. So, when we switch the plc to program mode, which place will always take the last scan ? tq.

[Ken Roach 194]

Are you using the real ControlLogix Redundancy system, with the 1757-SRM or 1756-RM modules, or are you attempting to perform a "warm backup" with your own logic and procedures ? I have used Prosoft MVI56-MCM and -MCMR modules in remote chassis with Redundant ControlLogix without any of the complications you describe.

[ChongKY1 1]

I'm not using the SRM card, I am just using control net and with a program to do the redundancy. This is the reason why I need to inhibit the MCM when switch to program mode. DO you have any ideas how to set it in the last scan ? or any others method to inhibit the MCM card when Plc switch to program mode. Tq.

[ChongKY1 1]

anybody know how to prevent user switch the plc to program mode ? thank you.

[BobLfoot 302]

This may be overly simple but if you remove the Keyswitch from the CPU then it is stuck in whatever mode it was in when you pulled the key. If you leave it in remote between program and run then RSLogix software can place it in program but not the user unless they have rslogix.

[ChongKY1 1]

Thanks. I even thought of putting some glue on it. haha. Can we do a delay for plc to switch to program mode when the operator switch the key to program mode ?