online simulating/problem

hi you have help me out a lot, why not this time too.
i,m using a mitsubishi melsec FX2n. i written a program that i have debugged completly using GX simulator. now i,m trying to do online simulating , the PLC is connected to computer with GX developer soft ware.
when i used the force on function on a output while the PLC is in stop mode , that output led was activated(no problem).
when i used the force(ctrl enter) function while the PLC is in RUN mode, i don,t notice anything on the output led nor on the bacth monitoring of that typical device. it seem that i cannot used this function while the PLC is run mode. can some one tell me what i,m doing wrong. or is this the way that GX developer fx work. if this the way how can i debugged a program online

When in ‘run’ mode, you can’t force outputs on, if the logic for that output is not true. (of course, if the logic were true, the output would be on anyway)

Neither can you force inputs on.

You can (as you say) force outputs on in stop mode. This is just for testing that one output only and ensures that the logic does not put anything else on as a consequence of forcing that output.

You can force internal bits on in run mode (M relays) but only if there is no associated coil with that bit.

Mitsi plc’s will not let you go against the logic.

When first learning plc’s it is often handy to build or buy yourself an input simulator. (A bank of switches basically)
You wire these to the inputs and can give a real test to your logic.

You have the FX-sim program. This will allow you to force inputs and outputs on because there is no danger from your actions. The sim program will do everything (?) the real plc will do, so you can debug using that.

To force inputs on, you can put a parallel spare M bit across it and force that on but that will only force one instance of the input.

Question,
This has been bugging me ever since this post started. Is the GX developer FX version different from the other GX developer version 7.11. I know I have forced many outputs on and off with my version of Developer. I have never put the plc in stop mode to do this, but I do know that if the output is in the program it won't let me. Now, I don't remember if I've ever done it on a FX2N. Is this where his problem is. I also just did this yesterday with an A2C plc. A co-worker of mine couldn't get his machine fault light to come on and I forced it on with the PLC in run mode and with the output in the program.
So, I guess I'm a little confused.
Tim

I am using GX Developer 7.11.
You cannot force output if the PLC is running and
rung with output is scanned. If the rung changes
state of the output, force will at best toggle it
for one scan...
When you tried to force an output and it worked
probably one of the following happened:
- rung was not scanned
- rung was scanned but toggling output allowed
it to seal in
- it was latched output and unlatch condition was not
true or it wasn't scanned

If you think none of this is true, try this:

   always_off                   some_unused_output1

------| |------------------------------( )





   always_on                    some_unused_output2

------| |------------------------------( )

Make sure both rungs are scanned and outputs are
not used anywhere else. Try to force on first or
to force off second output while PLC is running.
Let me know what happens

Alright,
Panic, I'm gonna hook up my plc to the computer. Give me a little while. I think I might just be confused on this. I've been working with Mitsubishi for 5 years now and thought you could do this. I'm not saying your wrong, I just gotta see it for my self.
Tim

OK Panic,
Can you tell me how I got these outputs to come on. BTW, you cannot manipulate the special relays "Always on and Always off", so yes your correct that I cannot force those two outputs on that you have posted. BUT, for jerrycat, he needs to turn on his output for program debugging purposes. I told him or her on another post that it could not be done if its in the program. I'm assuming that he's talking about the device test function and if the particular output thats being forced on is actually in his program it will not work. OPTIONS I gave him, 1. Delete the output temperarily and then force it on. 2.Force on every condition for that output by highlighting it with the BLUE BOX and hit shift enter. This is all done with the plc in run mode. I don't have any of these inputs actually turned on I just used shift enter to turn them on. Jerrycat also said on a previous post that he didn't have anything phisically wired up. Inputs, internal relays,counter, timers etc. can all be forced on. Whether the bit is being used somewhere else as an output, it will come on as well.

BTW,
Before someone gives me a code senerio. As Goody mentioned you cannot go against logic. My last sentence on my above post could be incorrect in some situations.

Fair enough, I think I owe some explaining...
I am not sure what GX designers or other control guys
understand by "forcing". Maybe that's why we have this
topic

To me, forcing I/O is the ultimate override control which
not just SETS but also MAINTAINS input or output (or any
other memory location) in desired state REGARDLESS what
program tries to do.

You couldn't do that with example I gave you above because
conditions used in rung are overwritting outputs.
Sure you can use "Test Device" function to SET value into
a register or an I/O. But you cannot FORCE.

More over, Mitsubishi's way of "forcing" is quite frustrating
because it is not consistent.
You cannot force an input to LOW state. If the sensor wired
to the input is high (input gets signal), that's what you have
to live with...
Actually this is same situation as our little experiment has
shown with the two output rungs. Anyway, I guess that's fine,
it a bit different from expected but it's ok...
Problem is that if you force an input HIGH, it does STAY high
regardles if signal at the input ih high or low!!!
Even worse, there is no indication that PLC is not in normal
run state (at least I didn't figure it out yet...).
To remove input forces, simply restart PLC (usually much faster than
manually forcing inputs OFF one by one).
May force be with you. beerchug

The way the Mitsubishi PLCs handle forces is kind of a pain in the ***. They don't work like you would think (the way they do with AB), but they force the bit once, and allow the program to change it back on the next scan.

I'm sure someone will correct me if I'm wrong, but it seems like the only way to totally force a bit is to remove its control rung, then use a force.

Tim,
gx developer Fx is used only for programming the FX-serie, where GX developer 7.11 can be used to program all mitsubshi PLCS, i think.