If I were to want to use Snap7 to implement something like that, I would create an FC that runs last in the highest cyclic OB # (like OB200 or higher if you have multiple OBs).

In there, I would add logic that maps snap7 M bits to Q bits.  To use Snap7 rather than PLC I/O directly, write an INT to an M tag, maybe M98 "UseSnap7".

For example, let's say Snap7 is configured to write M100 to M101 for digital outputs QB0 to QB1.

You can do it very simply with 2 MOV blocks, M100 -> QB0 and M101 to QB1.

If you want to override your Digital inputs, you need to replace EVERY logic element using digital inputs with M tags. 

Then in the first network of OB1, call an FC that checks the value of UseSnap7. If it is <> 0, override the digital input with the value sent via Snap7 to the M-tags you replaced all those DigIn tags earlier.

In those digital input mapped M-Tags, to make them easier to fine, I would probably name them something like in_0.0_Switch_1, in_0.1_Switch_2 and so on.  That way, the physical IO matches, and the tag names will be easier to manage and use during commissioning and troubleshooting.

HEHEEH

Hi experts, I am in need of help. Is there a way to use tools like snap7 python library to programmatically force inputs and outputs in the ladder logics ? currently it is possible to do that via force table on tia portal but not on code :(

I have only managed to use python code to modify the boolean Merker inputs in my simple ladder logic to turn my plc lights on or off.

the ladder logic looks like this:

digital input (%I0.0) OR switch (%M0.0) ----> light (%Q0.0)

Please send help thanks 

Not directly.

Yes, indirectly - as I posted earlier.

You can modify DB tags (bits, bytes, words, dwords) in the PLC using SNAP7 via Python.

In your PLC logic, you have the physical outputs set to whatever the DB tags are set to.

For example, let's say your PLC has a DB named "SNAP7_out" with some tags like Q0.0, Q0.1, Q0.2, ...

In the PLC logic (SCL for simplicity):

Q0.0 := "SNAP7_out"."Q0.0";
Q0.1 := "SNAP7_out"."Q0.1";
Q0.2 := "SNAP7_out"."Q0.2";
...

You can do the same in LAD:

"SNAP7_out"."Q0.0"                    Q0.0
----| |--------------------------------( )---

Just make sure SNAP7_out DB is configured as non-optimized so Snap7 can easily use it, and PLC security allows SNAP7 to use PUT to that DB.

AutoGen_5845758

Please could you help me. I want to know it is possible to change my plc output states with a python code using snap7. 
I am currently trying to set or reset my plc outputs with a python code. I tried  a python script, you can see it attached but it doesn't work. 
if you have any issue, i will be grateful.