Hi ,
could you please let me know when the expression position & vector is checked in the below code. is it only when the constructor of cover group called or each time when ever sample function of cover group called.
covergroup cgmaskbit(input bit [31:0] position, ref bit [31:0] vector);
pos: coverpoint (position & vector) !=0;
option.per_instance = 1;
endgroup
cgmaskbit cgmaskbits[32];
foreach (cgmaskbits[i]) cgmaskbits[i] = new(1'b1<<i,m_csr_intr_mask.interrupting_csrmask);
In reply to srbeeram:
yes, when the sample() function is called.
Here is an example from my SVA Handbook 4th Edition, 2016
module coverx;
bit clk, smpl;
logic[3:0] a=4'b1XZ0;
initial forever #10 clk=!clk;
always @ (posedge clk) begin : aly
smpl <= 1'b1;
t_cg.sample(); // <-----------------------------The sample of t_cg
@ (posedge clk);
smpl <= 1'b0;
a=4'b0010;
end : aly
// If cp_a coverage is ture, then an X or a Z was observed
cp_aXZ: cover property(@ (posedge clk iff smpl) $isunknown(a));
ap_aNoXZ: assert property(@ (posedge clk iff smpl) $isunknown(a)==0);
function automatic int countbits(logic[3:0] v);
automatic int s=0;
for (int i=0; i<= 3; i++) begin
if (v[i]===1'bX || v[i]===1'bZ) begin
s=s+1;
$display("is X or Z");
end
end
$display("%t v=%b, countbits=%d", $time, v, s);
return s;
endfunction : countbits
covergroup a_is_x_cg;
type_option.merge_instances = 0;
option.per_instance = 1;
option.get_inst_coverage = 1;
cp_unknown: coverpoint $isunknown(a)==0;
// ($isunknown ==0) i.e. true then no X or Z
cp_with_countbits: coverpoint countbits(a) ==0 ;
cp_with_countbits_axz: coverpoint $countbits (a, 'x, 'z) ==0; // 1800-2012
// ($countbits (a, 'x, 'z) ==0) then no X or Z
endgroup
a_is_x_cg t_cg = new; // instantiation of covergroup <<---------------------------
endmodule : coverx
Ben Cohen
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