Re: [sv-ac] sv-ac: quick clarification questions of checker update regions

  Tom,
One more question; For the new proposal, what if x, y were *rand* variables,
 is below correct on sampling and updates?

checker check(bit a, b, event clk, ...);
 * rand bit x, y, z, v;*

  always_comb
    y = a & b; // legal, changed in the Reactive Region?
  always_ff @clk
 // x sampled in the preponed region.
 // z updated in the Re-NBA region
    z <= !x; //
endchecker : check

module m;
   logic clk=0, a, b;
   initial forever #10 clk=!clk;
   check chk1(a, b, posedge clk);
    ...
endmodule : m

On Mon, Jun 6, 2011 at 3:28 PM, Thomas J Thatcher <
thomas.thatcher@oracle.com> wrote:

> Hi Ben,
>
> For IEEE 1800-2009, continuous assignments are not allowed in checkers.
> So the assignment to x would not be legal, and it was not defined when x
> would be sampled. Dmitry's proposal (3033) would allow continuous
> assignments within checker, and they would update in the Reactive region.
> So the assignment to x would take place in the Reactive region.
>
> Non-blocking procedural assignments are currently updated in the Re-NBA
> region. This does not change. Previously, in 1800-2009 non-blocking
> assignments could only reference checker inputs or other checker variables
> assigned by non-blocking assignments. The non-blocking assignments would
> see the sampled value of any checker inputs, because all checker inputs were
> sampled, and it would see the current value of any other checker variable.
> Dmitry's proposal would change things so that checker inputs are not
> automatically sampled. However, any variable referenced by the RHS of a
> non-blocking assignments would be sampled.
>
>
> So if Dmitry's proposal is enacted,
> 1. x & y updated in the Reactive region
> 2. z updated in the Re-NBA region, x sampled in the preponed region.
>
> Tom
>
>
>
> On 06/05/11 23:28, ben cohen wrote:
>
>> Questions: or model shown below: 1) When is "x" sampled? Active Region 2)
>> In what region is "z" changed? In the Reactive?
>> 3) are my comments correct?
>> checker check(bit a, b, event clk, ...);
>> bit x, y, z, v;
>> assign x = a & b; // legal, changed in the Reactive Region? always_comb
>> y = a & b; // legal, changed in the Reactive Region? always_ff @clk
>> z <= !x; // , x sampled in active region? z changed in Reactive?
>> endchecker : check
>>
>> module m; logic clk=0, a, b;
>> initial forever #10 clk=!clk;
>> check chk1(a, b, posedge clk); ... endmodule : m Ben
>> --
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>

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