I am programming ControlLogix Ladder Diagrams using RSlogix 5000. I bought a chassis with a Processor only. There are no I/O modules. The processor can talk with my Laptop using serial communication port.

When I go online with ControlLogix processor, I found an interesting issue: I cannot TOGGLE every XIC and OTE. I also cannot FORCE ON every input and output address (both DI and AI). Could any expert tell me what is going on?

 

I don't know about the forcing, but if there is code in the processor, it is entirely possible that the code is resetting the toggled bit. Using the programming software to trun the bit on or off, does not prevent the plc code from affecting its state.

 

Billy, Using TOGGLE does not force or override a bit/bool that is already being set or reset, all it does is toggle the stat of that bit. If you have an OTE and tried to toggle it then quite likely the logic to the OTE is setting/resetting the bit and your TOGGLE does nothing or may change the state for one scan.

FORCES only work on digital IO and not on internal bits, the same as it does for SLC and PLC5's.

And FORCES do not work on Integers/Reals at all, meaning that they will not FORCE Analogue IO. You can do a similar thing with a Integer or Real tag by typing in a relevant value in as the data, but if something else is 'writing' data there then it will be over-written, for example an Analogue input module.

Regards,
Trevor.

 

Thanks a lot, Bob,

I am wondering anybody else has more ideas about this?

 

Thanks you so much Trevor. You helped me a lot.