RE: [sv-ac] usage of .triggered on a sequence

A quick follow-up: I have access to only one simulator right now, so this is
not in any way authoritative, but for a reguar event E I got this behaviour:
 
* at a time when E is not triggered at all, wait(!E.triggered) proceeds without delay;
* at a time when E.triggered is true, wait(!E.triggered) locks-up for ever!
 
I suspect this is a bug in the tool, but it's easy to understand why it might happen. 
You are right that the LRM says nothing explicit about this, but the descriptions
of .triggered clearly imply that it's just an expression.

	For regular events (which also have a .triggered method) the situation is fairly clear:
	E.triggered becomes true (value 1'b1 of type bit) when the event is emitted, and becomes
	false at the end of the timestep, that is, on exit from the Postponed region.  User code
	has no access to that, so it is completely safe for user code (and PLI) to assume that
	E.triggered remains true throughout the timeslot and is false at the beginning of the
	next timeslot, whenever that next timeslot may be.
	
	I would imagine that the behaviour of SEQ.triggered should be analogous.  Certainly,
	I have written code that relies on such behaviour, and it *seems* to work :-)
	
	Since <anything>.triggered is just an expression of type bit, there is presumably no
	difficulty in waiting for or testing its inverse.  The semantics of wait(!E.triggered) are
	a little bizarre,  though...  continue execution without delay if E.triggered is false,
	otherwise wait until simulation time advances... 
	
	        Currently LRM only has examples where .triggered property is checked for its positive value. E.g.
	          wait (s0.triggered) or if (s0.triggered)
	        
	        Is it allowed to check for the negative value of .triggered ? E.g.
	          wait (s0.triggered == 0) or  if (s0.triggered == 0)
	        
	        It is clear in the LRM when the value of .triggered becomes 1 (in Observe region) but there is no clarity on when it becomes 0 (i.e. in which region ?).
	        
	        If checking for value 0 is allowed, when should a wait statement should unblock ?
	
	
	Regards
	
	Jonathan Bromley
	
	
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