RE: [sv-ac] Sketch for the new version of 1756

Hi Dmitry,
 
I think that solution(2) is not convenient because these tasks already
have a variable list of arguments, it is not then easy to distinguish.
 
ed
 


________________________________

	From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf
Of Korchemny, Dmitry
	Sent: Tuesday, October 30, 2007 9:14 AM
	To: sv-ac@eda.org
	Subject: [sv-ac] Sketch for the new version of 1756
	
	

	Hi all,

	 

	Since there were objections regarding the solution proposed in
1756 I had an action item to send a sketch of other potential solutions
for this enhancement.

	 

	The problem:

	 

	All concurrent assertions belonging to initial procedures, are
suppressed in case that at the initial time $asserton or $assertkill
control tasks was issued. However, this behavior is not always
desirable, and there should be a method to start checking these
assertions as soon as an appropriate $asserton control task has been
called.

	 

	Consider the following scenario:

	 

	The assertion is written to check that a eventually happens

	 

	initial a1; assert property(@clk ##[*0:$] a);

	 

	but $assertoff has been issued for all assertions at the
beginning of the simulation to skip the reset sequences. When $asserton
is issued, the above assertion is lost.

	 

	The original proposal suggested that in case the assertions have
initially been disabled, start checking them when they are enabled for
the first time.

	 

	The objection claimed that this enhancement is not backward
compatible, and also, there is a problem when the user intention was
indeed to suppress the assertions in the initial procedures.

	 

	Here are two possible backward compatible solutions:

	 

	1.	Introduce a new directive $assertdelay. If it has been
issued at the beginning of simulation, all assertion checks are
suspended until the first $asserton. 
	2.	Introduce an additional optional argument to the control
tasks $assertoff and $assertkill. If it is 0, then their behavior is as
it is described currently in the LRM. If it is 1, and these directives
were issued at the beginning of the simulation, the concurrent
assertions in initial procedures are checked when they become first
enabled.
		E.g., $assertoff(a1) - initially issued disables the
assertion a1 forever, $assertoff(a1, 1) delays checking  the assertion
a1 until the first $asserton(a1) is issued. 

	 

	What is your opinion?

	 

	Thanks,

	Dmitry

	 

	
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