We now use PLCs with OPC servers built into the the CPU, eg S7-1500.
With a decent ethernet link you can read all sorts of stuff out of them.
This coupled with a state machine approach generally gives good certainty and knowledge.
With a decent ethernet link you can read all sorts of stuff out of them.
This coupled with a state machine approach generally gives good certainty and knowledge.
Unfortunately not every protocol is like that and not everyone adopts it :(