How to show waveform in Vivado simulation window? The waveform is absent for some signals.

Question

Hi,
I have the following verilog code:
`timescale 1ns / 1ps
module top(
reg clk = 1;
always
#1.25 clk <= ~clk;
wire temp;
//wire temp2; // added later
assign temp = clk;
//assign temp2 = clk; //added later
endmodule
 When I simulate this, I see "CLK" as expected but "temp" just has the value 1 and no waveform. When I uncomment the lines marked as "//added later", I can see "CLK" and "temp2" waveforms as expected. But "temp" is still stuck at 1 and there's not waveform for it.
Then I commented the lines marked as "//added later" again and there's not waveform for "temp". Then I renamed "temp" to "temp2" and simulated. This time I could see "CLK" and "temp2" waveforms in the simulation window toggling as expected.
It could be that I'm just not seeing the waveforms. For example in the first scenario, I'm just seeing a "1" and no waveform. There are also some other signals that when added to the wave window don't show a waveform. How can I enable the waveform?
Thanks,
 

Answer 1

I tried using a separate module for clock generation as you suggested. In my top level module I instantiate two clocks "CLK_20MHz" and "CLK_25MHz". When I simulate I can see the waveform of both clocks. Then, from the clock module, I add the register "CLK". However, I see no waveforms for "CLK". But when I add "$monitor("%d,\t%b",$time, CLK);" inside the clock module, I can see in the logs that "CLK" is actually toggling as expected. I don't know why the simulation window doesn't show the waveform? And how I can show/enable the waveform?