同步上升沿检测

module cy4(
       input clk,
       input rstb,
       input sig_a,
       output sig_a_risedge
          );
reg sig_a_d1;
always @(posedge clk or negedge rstb)
  if(!rstb) sig_a_d1 <= 1'b0;
  else sig_a_d1 <= sig_a;

assign sig_a_risedge = sig_a & !sig_a_d1;

endmodule

测试脚本代码
`timescale 1 ns/ 1 ps
module cy4_vlg_tst();

reg clk;
reg rstb;
reg sig_a;
// wires
wire sig_a_risedge;

cy4 i1 (

.clk(clk),
.rstb(rstb),
.sig_a(sig_a),
.sig_a_risedge(sig_a_risedge)

);
initial
begin
sig_a = 0;
clk = 0;
rstb = 0;

100;

rstb = 1;
sig_a = 0;

100;

sig_a = 1;

100;

stop;$stop;$display(“Running testbench”);
end
always #20 clk = ~clk ;
endmodule