How do I start a clock after a delay of 5ns?

Question

In my project, I need two separate clocks, but one of them, bit_clk needs to be started after a delay of 5ns. How can I do that?

`timescale 1ns/100ps
always #40 clk =~ clk;
always #5 bit_clk =~ bit_clk;

Answer 1

You can delay the start of a clock by using a forever loop inside an initial block:

`timescale 1ns/100ps

module tb;

bit clk, bit_clk;

always #40 clk =~ clk;

initial begin
    #5; // Delay before starting
    forever #5 bit_clk =~ bit_clk;
end

endmodule