[SOLVED] Verilog-A pulse generator

[gemass]

Hi,

I'm new to verilog-A and I use the following code to detect the first falling edge of my input signal (Vin) and generate a pulse of 0V for 10ns at my output signal (Vout) as soon as the falling edge of Vin is detected, throught the @cross function, and also at time 0 with @initial_step(it creates a reset pulse):

module allo(in,out);
parameter real td = 10n;   // width of pulse
parameter real tt = 0n;	// output transition time (s)
parameter real t1 = 0n;

   output out;
   input in;
   voltage in, out;
   real Vout, tend,rst;

analog begin

	@ (initial_step or cross(V(in)-1, -1)) begin
		 Vout = 0;
		 tend = $abstime + td;//return simulation time + td
	  end

	  @(timer(tend))
		 Vout = 1.8;
		 V(out) <+ transition(Vout, td, tt);
	   end
endmodule

The problem is that, for a certain reason, a pulse of 20 ns is generated even thougth I specify a value of 10 ns (td=10 ns) and only the second falling edge of my input signal is detected (at 75.21 ns)while I want the one at 65.24ns to be detected. How can I change my code in order to detect the first falling edge of my input signal Vin ?

Thanks for your help !

 

[gemass]

my bad, I have put two delays of 10ns..one in @cross and the one in the transition function...