Forcing PLC I/O

[presario2100]

Hi guys: I'm using GPPW SW4D5-GPPW-E Ver4.0 to programming the PLC, I have question need to ask, how to forcing the PLC I/O. I tried use "Device test" section to force the I/O, but it's not working. Did any Mitsubishi FX series expert here know why ? Please, really need your help.

[Rodney]

Mitsubishi P.L.C.s are not the same as some other P.L.C.s that is to say if you force I/O they are forced on and remain on until they are reset or forced off. Mitsubishi P.L.C.s will only force on for one scan of the P.L.C. if there is nothing in the program to keep the output on. The input will only be on for the single scan because the input is off else why would you force it on in the first place. Rodney

[FNMdeJong]

It is also depending on the used system, FXxN, A-series or System Q. An output is only for one single scan and a input can be overruled. That means the input remains high untill it is forced low again. (even a reset of the PLC is not helping)

[Colin Carpenter]

You can happily force outputs ON as long as the PLC is not in the RUN position. I often do this to test the wiring prior to running the programme. Failing that, as others have said, you can include, if you want to, an extra M coil in parallel with the normal code that drives the output. This M coil will not be referenced by the programme, only by the programming software (or HMI if you want a "manual" facility).

[panic mode]

as you already know by now, forcing in Mitsubishi means SET and that's fine unless program is running and there is logic that can change state of that emory location. be careful when forcing inputs, they behave a bit different. if actual input is low, you can force it high but not the other way around. also if you force input high, it stays high even if actual input changes. it is not bad idea to restart plc after testing, just to make sure all input forces are reset.

[panic mode]

Please try not to start new topic, when one is already there. It makes it easier to offer help. The only "forces" in GPPW are ones you tried already. (Device Test, Force...) If your program is running, you can stop PLC first and then use this feature.

[Regelink]

In GX Works3 I can set a digital input (e.g. X0) to ON or OFF in the Watch window when connected to an FX5U. When it is set to ON like this, it remains on regardless of whether the real input is driven high or low externally. When it is set to OFF but the real input is driven high, it will change to ON.

I can only do this from GX works3, but I'd like to do it from the PLC program (for testing purposes) as well. I know something is done in the PLC to do this, since even when I close GX Works3 and reconnect to the PLC, the state for X0 remains. So, my question is, is it possible to force X0 to ON from within the PLC code regardless of what is physically connected to the input, perhaps using some special register or function?

[SergeyBorchshev]

No you cannot force physical inputs on Mitsubishi. For outputs you can use Always on bits (m8000, sm400) depends of the PLC type. Or you can use unused Bit M*** and flip the state of that bit with Shift+Enter while online with PLC (I always use M from non-latching range, so it would reset with power OFF)

Or use SET/RST to drive your input, it works in simulation for me.

Edited October 4, 2024 by SergeyBorchshev