I have a question about RSLogix 5K.

Hello

If you were to loose the program in a cpu would all communication modules read OK and would the cpu stay in run. I have some understanding of RSLogix 5K but I had never ran into that before myself. I was wondering if its possible? Other brands I've seen when the program is lost the processor is taken out of run.

Tom

While some people refer to a ControlLogix controller as having "lost" a user program, in fact it erases the user program if it is judged to have been corrupted.

So the simple answer is no: a program that's been erased cannot also be running, and the controller cannot be in RUN mode. It will always be in FAULT mode.

It *is* possible for I/O connections to fault into a "hold last state" mode if they're configured that way.

hmm sounds odd.. when I've lost a program the modules installed would be incorrect and it would fault

regardless of what made the program "go away" it IS possible for the "RUN" LED and the "OK" LED on the front of the processor to both be lit (solid green) even though there is NO program in the processor ... (bad battery with a loss of power is one common situation that can dump a program) ...

is that what you were asking? ... it's a very common question - and VERY confusing to the third-shift technician who "thinks" that the processor is running (based on the LEDs) but can't imagine why nothing is being controlled ... incidentally, older processors (PLC-5, SLC-500, etc.) don't act this way ... specifically, they can't "run" without a program - but ControlLogix and CompactLogix processors can ...

going further:

you specifically mentioned "communication" modules ... did you mean ALL I/O modules instead? ... there can be a difference ...

Ron's right about this, technically.

If a ControlLogix CPU detects a corrupt program it absolutely will erase that program and fault. If a ControlLogix CPU has the power cycled with no battery (L1, L55, L6/A controllers, etc) it will also erase the user program.

If you cycle the keyswitch or the power, the controller will have an empty program with no I/O connections and no logic. This program can run, with a solid green I/O LED (no connections) and a solid green RUN LED (no logic).

What the controller DOES NOT DO is go from "running an application program" to "running a default null application program" without going through a Major Fault condition or a power cycle first.

I agree that without some context it's hard to answer this question effectively.

wolverine1981 said:

....would all communication modules read OK.....

Tom

Click to expand...

Ron and Ken have covered the CPU and "run" so I will address the communications portion.

Your communications modules will still continue to operate. The status of the LED indicators will vary depending on the network and whether you have I/O connected. If you are more specific, we can tell you more. Or take a look at the user manual. It's built into the RSLogix software (Help - Online Books).

Your Ethernet and ControlNet modules will still allow you to connect and communicate. However, with no program in the CPU, any I/O connected using the communication module will be affected. Again, the I/O modules are configurable for what you want to happen to each I/O in this event.

OG

I was in on a conversation with a co worker that worked the night before. And stated that everything looked fine but the machine would not run. And the lead said he beleived the program was missing and reloaded it. I had my doubts due to I had never seen this before and the time it took to resolve. I just wondered if it was a possability.
Ah I should have stated ethernet communication modules.
Thank You form the night shift for replying so fast and have a GREAT night sleep.

Tom