title: How can I use $value$plusargs in verilog?
body: <p>I'd like to use "$value$plusargs" as the below cede,</p>
  
  <pre><code>module top();
  ...
  reg data;
  real READ_FREQ
  
  initial begin
  if (!$value$plusargs("READ_FREQ=%0F", READ_FREQ))
   READ_FREQ = 197;
  end
  
  parameter wclk = 300;
  parameter rclk = READ_FREQ;
  
  always #(rclk/2.0) i_rclk = ~i_rclk;
  
  ...
  endmodule
  </code></pre>
  
  <p>but when I compile above code, I've got error such as </p>
  
  <pre><code>irun: *E,VLGERR: An error occurred during parsing.  Review the log file for errors with the code *E and fix those identified problems to proceed.  Exiting with code (status 1).
  
  irun(64): 12.10-p001: (c) Copyright 1995-2012 Cadence Design Systems, Inc.
  file: ./top.v
  parameter       rclk      = READ_FREQ;
                                           |
  ncvlog: *E,NOTPAR (./top.v,197|41): Illegal operand for constant expression [4(IEEE)].
  </code></pre>
  
  <p>How can I use $value$plusargs in verilog?</p>