Hi All ,
Section 19.3 of the LRM states :
If the clocking event occurs multiple times in a time step, the coverage point will also be sampled multiple times
I was curious on how a clocking event could occur multiple times in same time step .
Would be helpful if someone could provide a small example of the same
In reply to MICRO_91:
Here is an example where the variable k has 2 events in a time step.
module m;
bit [4:0] a;
bit clk, b=0, c, k, w, q;
initial forever #5 clk = !clk;
always @(posedge clk) begin
a <= a + 1; b<=!b; c <= 0; end
ap_1: assert property (@(posedge clk) b |-> c)
else begin k=!k; w=!w; end
// k and w change in the Reactive region
// ap_2 is scheduled in the Observed region in the loopback
ap_2: assert property (@(k) b |-> c)
else w=!w;
// ap_2 is processed in the lopback in the Observed region
// and w toggles again
//THUS, in that same time step w has 2 transitions
initial begin
$dumpfile("dump.vcd"); $dumpvars;
repeat(6) @(posedge clk);
$finish;
end
endmodule
If I write the following, I would have clocking event occurs multiple times in a time step,
covergroup g1 @(w);
c: coverpoint color;
endgroup
Ben Cohen
http://www.systemverilog.us/ ben@systemverilog.us
** SVA Handbook 4th Edition, 2016 ISBN 978-1518681448
…
In reply to MICRO_91:
There are many convoluted ways.
bit b,c;
initial repeat (20)
begin
c <= !c;
@c;
end
covergroup cg @(poesedge c);
coverpoint b {
bins bs[2] = {0,1};
}
endgroup
cg cgi=new;
In reply to dave_59:
Hi Dave ,
Your code invoked an interest to understand the Region where sampling occurs :
I tried 2 variations ::
// Code 1 ::
bit [1:0] a ;
bit clk ;
covergroup cg1 @( posedge clk ) ;
a_auto : coverpoint a ;
endgroup
cg1 cg_1 = new() ;
initial forever #5 clk = !clk ;
always @ ( posedge clk ) a <= a + 1 ;
// CODE2 ::
bit c;
initial
repeat (2)
begin
c <= !c; @c;
end
covergroup cg @(posedge c);
coverpoint c // For 0 -> 1 transition , c would be sampled 1
{
bins bs[2] = {0,1};
}
endgroup
cg cgi = new ;
For 1st case : 3 bins corresponding to values of a = 0 , 1 , 2 are covered .
For 2nd case : bin corresponding to value of bs[1] is covered .
Can I say the coverpoint expression in sampled in Active region ?
In reply to MICRO_91:
The sentence before the one you quote in section 19.3 says “a coverage point is sampled the instant the clocking event takes place”. This means the covergroup does not care about event regions. The sampling takes place in the region the event occurs.