Hello,

I expect that you know sequence of execution of blocks. You can't start Modbus_Master block first if you don't have correctly passed Comm_Load block - DONE true and no ERRORs. Pay attention to this. You can't also check STATUS visually from VAT or DB Online, you need check them in code via some created conditions.

Hello,

again, you need check important outputs from blocks programatically, create conditions for that. Then after init of Comm_Load block you can easy check DONE, ERROR, STATUS values. Pls, I expect from your info that you're using DONE bit to Master's execution. Pls don't do this via this system. Create condition for DONE snd set some other free Merker/TAG and this use for start of Master block f.ex. General recommendation is save STATUS value in case of ERROR bit is true, so create conditions in your code. Then you'll better chance to find problem what you have...

Update: maybe you can also make test (in case you'll have DONE true), that you reset REQ of Comm_Load after success DONE. only after that try start Master block execution. Simply I make this for initial tests (REQ of blocks) with different Merkers and set them manually to see conditions results and then execute my required blocks.