Which functions do the different variable types have for the individual messages?
- Event variable:
This variable triggers the message (incoming and outgoing state).
- Acknowledge variable:
If a message is acknowledged, then this bit is set to "1". In this way you can evaluate in the controller.
In WinCC version V4.02 and higher this bit can also be changed in the controller and the message is then displayed as acknowledged. You can thus acknowledge the message in the SPS or from another computer, and the message is also displayed as acknowledged on the local computer.
- State variable:
You can use an 8-bit, 16-bit or 32-bit value without sign as state variable. If the bit "0" is selected as state bit, then the following assignments are valid for further state processing depending on the data type used:
Assignment state bit
8-bit without sign
16-bit without sign
32-bit without sign
Function of the state variable with a 16-bit value with state bit "0" selected:
Bit "0" is set to "1"
Message must be acknowledged
Bit "8" is set to "1"
Message is acknowledged
Bit "8" is reset to "0"