First out block

Dear team,

We have an requirement of first out block , which can tell which event call for DO activation.

Do anyone has prepared such block .

If yes, please share

What is a "DO activation"?

We have written a logic in hardware, which activate my relay i.e DO block.Now my customer demanks to know, which input signal Activa which call for Module DO activation

I've typically seen the first out logic added to the PLC code.
Then in the SCADA package you would simply read the first out boolean from the PLC, and add an alarm to it.