RE: [sv-ac] Sampled value function $past $rose $fell

Hi Soumya,

I assume that you are talking about $past(b,2, ,@(posedge clk1));

Suppose that clk ticks at time 100 (when a also happens) and 200, when $past is checked, and clk1 ticks at time 150 and 170. Then $past(b,2, ,@(posedge clk1)) will take the sampled value of b at time 150 (two ticks of clk1 back). If it is 1, the sequence sq1 will be matched at time 200.

Though it is not directly related to your question, I am not sure what your intention was in assert1: it means that a is always true starting from the second tick of clk and b is always true in some moments that depend on mutual patterns of clk and clk1. Also, if the second tick of clk1 does not happen before the second tick of clk (e.g., if clk and clk1 are the same clock) the assertion will fail.

Regards,
Dmitry

-----Original Message-----
From: owner-sv-ac@server.eda.org [mailto:owner-sv-ac@server.eda.org] On Behalf Of soumya
Sent: Tuesday, January 13, 2009 12:12 PM
To: sv-ac@server.eda.org
Subject: [sv-ac] Sampled value function $past $rose $fell

Hi,
 Please consider this sequence and property.

sequence sq1;
@(posedge clk)  a ##1 $past(b,2, ,clk1);
endsequence

property prop;
@(posedge clk)##1 sq1;
endproperty

assert1: assert property(prop)

$past has clk1 in his argument , but the sequence or property has clk.
Both this clk and clk1 are different.
My question is that while sampling which clock should $past take, clk or
clk1? In place of $past, if $rose or $fell used then what will be the clock?

Thanks,
-Soumya


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