[sv-ac] Issue #1550

Hi all,

 

During the discussion of #1550 a question was raised whether we need to
keep a second argument of $sampled function. The current definition is
$sampled(expression [, clocking event])

 

If we want to keep it then its semantics should be:

 

$sampled(expression, clocking event) = (clocking event) ? expression :
$past(expression, clocking event). The straightforward synthesis without
a system clock is not clear in general case.

 

E.g., always a = $sampled(b, @(posedge clk))

or

disable iff ($sampled(reset, @(posedge clk))

 

 Therefore we have three options:

1.	Allow only one argument form, which is not backward compatible
2.	Allow two argument form in trivial cases only, e.g., always
@(posedge clk) a = $sampled(b, @(posedge clk)), which is redundant
3.	Allow two argument form in trivial cases or when a system clock
is present (I have a proposal about a system clock in one of my
presentations)

 

What do you think?

 

Thanks,

Dmitry