20ns pulse generation at rising edge

[Altera_Forum]

Hello,  

I'd like to generate a 20ns high signal at the rising edge of another (clocked, 330ns) signal. Formally, they are a 50MHz clock and a 3MHz clock. Right now, I am stuck at the very beginnin' of this task. I mean, I found many codes that can generate a pulse if a rising edge condition is meet. Anyway, there's no control on the pulse duration.  I was thinking of a signal locked at the rising edge of the 3Mhz signal to trigger a state machine clocked @50Mhz. My problem is that I can't figure out how to deassert the trigger signal, since it will deassert on the next rising edge of the control signal.  Here is a (wrong) code I made since now - i didn't include resets here to make it easibily readable.  I don't expect a solution, or it to work. I'd like just a hint.    --- Quote Start ---   always@(posedge 3Mhz_signa)  begin  up<=1; end  always@(posedge 50Mhz_signal) begin  case(fsm)  0:begin;  data_out<=0;  if up(fsm<=1);  end  1:begin;  data_out<=1;  fsm<=0;  end  endcase endmodule   --- Quote End ---   how can i deassert "up" signal after 20ns, being locked to posedge 3Mhz clk? I was thinking of a sort of "feedback", but still not ideas.  EDIT:  i seems like I didn't search enough on google.  I found out this (http://www.oldcrows.net/~patchell/iparchive/oneshot.v) that's exactly what I needed. Basically, feedback was the right way.  I've a long way to proper learn coding.

[Altera_Forum]

So you need your trigger to be aligned with the rising edge of the 3 MHz clock and then go low 20 ns later? Did I understand you correctly? This is not possible with the clocks that you have.  

 However, you can make a 20 ns pulse when a rising edge on 3 MHz is detected using the 50 MHz clock. The issue with what you are trying to do is that the 3 MHz and the 50 MHz clocks are not synchronous.   /Boris

[Altera_Forum]

I wanted a pulse generation triggered by the rising edge of the 3MHz Clok - I understand your point now, you're right.  

Anyway, the link I posted seems to be fair enough for my purpose, right now. I'll be back on the pulse generation, maybe.