For Verilog 2005, when writing the test bench, is it possible to create a lookup table of delay values, and then assign a certain value in it to be the delay of some procedural block?

For example:

reg        clk;
reg  [9:0] delay [0:15]; //suppose delay[i] = 10'di;

always #delay[i]
    clk <= ~clk;

and I somehow change i to read out a certain delay value.

Moreover, is it possible to make a lookup table of delays with floating point values?


An array of 16 floating point elements: real delay [0:15];.

Within the always block, a wait statement is needed to allow the delay values to be populated. Because it is a clock, I suggest adding a condition checker to terminate the simulation if it fails. This safeguard is to catch 0-time infinite loops while the simulation is running.

reg clk;
integer i;
real delay [0:15];

always begin
  wait( ^i !== 1'bx); // This gives us a change to populate delay
  if (delay[i] <= 0.0 || i < 0 || i > 15) begin
    $display("FATAL @ %0t :: Something gone honorably wrong. i:%0d range 0 to 15, delay[%0d]:%0f",
  clk = ~clk;

Working example


Here delay[j] is a look up table of real values which can be varied in the expression "delay[i]=1.2+i". This real valued delay can be used as setting time period for a clock in always block as shown below.

`timescale 1ns/1ps
 module del;
 real delay[0:15];
 integer i,j;
 reg clock;

 initial begin
 for(i=0;i<16;i=i+1) begin
  delay[i]=1.2+i;  //can be any expression such that delay can be a real value

 initial begin
 j=3;  // Can be any integer
 #400 $finish;

 always begin
 #delay[j] clock=~clock;

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