My favourite technical diagrams are:
UML Sequence charts
Good for describing time sensitive things like obtaining locks.
BPMN business process models
You might be super interested in that because it supports clicking to expand the parameters on the states. Its has an XML representation too so its both machine readable, visual and executable. Its used in very boring places in non-tech companies but its pretty nice technology IMHO that has gone a few rounds of standardisation. Can model human/computer processes spanning long time horizons (e.g. submitting an insurance claim, yawn!)
UML State diagrams
Hierarchical state machines solve the state space explosion problem of finite state machines. Pretty cool but fairly narrow domain of applicability IMHO. I think they make great protocol representation.