VHDL process for blinking led
<p>I would like to have a process which make a led blinking 3 times (each time the light should be on for one second) and the interval between to light-on should be of 1 second.</p>

<p>The fastest and easiest way should be the following:</p>

<pre><code>process(CLK)
begin
....
led &lt;= '0';
led &lt;= '1' after  1 sec,
 '0' after 1 sec,
 '1' after 1 sec,
 '0' after 1 sec,
 '1' after 1 sec,
 '0' after 1 sec;
....
end process;
</code></pre>

<p>By compiling it there is no Error... but the clock has its own working frequency (e.g. 1ns). By tring this code with Modelsim it will give the following error:</p>

<pre><code>run
# Cannot continue because of fatal error.
# HDL call sequence:
# Stopped at C:/User...rm.vhd 50 Process line__41
# 
</code></pre>

<p>The row is exactly on the PROCESS(CLK) row.</p>

<p>I think the problem is because the CLK has bigger frequency so in this way a next process starts before the previous finished (it makes something really nasty...).</p>

<p>If what I wrote is correct, a solution can be playing with the clock for having the requested period but I would like to find a faster and more light solution.</p>