RE: [sv-ac] SVA - $sampled

My point is that the clock is not needed and if you do use the clock
explicitly it is not clear what you get. It would depend on whether you
evaluate the function before or after the clock tick happens in the same
time step. E.g., in a continuous assignment.

ed 

> -----Original Message-----
> From: Bassam Tabbara 
> Sent: Wednesday, May 10, 2006 2:21 PM
> To: Eduard Cerny; sv-ac@eda.org
> Subject: RE: [sv-ac] SVA - $sampled
> 
> Ed I am missing something here:
> 
> A) clock is already optional (and can be inferred from context)
> B) It is mostly understood that all these functions always sample in
> preponed (whether inside or outside) assertion context.
> 
> So I claim this is largely not needed -- ??
> 
> Thx.
> -Bassam.
> 
> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of
> Eduard Cerny
> Sent: Wednesday, May 10, 2006 11:14 AM
> To: sv-ac@eda.org
> Subject: [sv-ac] SVA - $sampled
> 
> Hello,
> 
> while discussing Dmitry's comments regarding the sampled 
> value functions
> $rose, $past etc., I think we should also review the definition of
> $sampled as outlined below. If you agree that this is useful I will
> enter it in Mantis.
> 
> Best regards,
> ed
> 
> ----------------------
> 
> Currently $sampled is defined as follows:
> 
> ---
> $sampled(expression [, clocking_event])
> 
> Function $sampled returns the sampled value of the expression with
> respect to the last occurrence of the clocking event. When $sampled is
> invoked prior to the occurrence of the first clocking event, the value
> of X is returned. The use of $sampled in assertions, although allowed,
> is redundant, as the result of the function is identical to 
> the sampled
> value of the expression itself used in the assertion.
> ---
> 
> The use of this function outside of assertions and assertion action
> blocks is rather difficult. 
> 
> Yet it is useful in assignments to auxiliary state variables of
> assertions, once changed as follows:
> 
> ---
> 1) Remove the clocking event:
> 
> $sampled(expression)
> 
> 2) Change the description to:
> 
> Function $sampled returns the value of the expression at the prepone
> time of the current simulation time unit.
> ---
> 
> With this definition, it is possible to have
> 
> reg auxiliary_state;
> 
> always @(posedge clk)
>    auxiliary_state <= funct($sampled(some_input));
> 
> in which case the auxiliary_state is assigned the same value 
> as seen by
> an assertion over some_input.
> 
> 
>