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Modeling >> Behavioral Models >> cannot filter out short pulses
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Message started by Pavel on Jul 27^th, 2010, 12:50am

Title: cannot filter out short pulses
Post by Pavel on Jul 27^th, 2010, 12:50am

Hello,

I want my latch to filter out short pulses (shorter than 0.15ns).
But in spite of standard it doesn't. Here is code:

Code:

`timescale 1 ns / 1 ps

module Latch(nD, nGate, Q);
input nD, nGate;
output reg Q;

always @(nGate, nD)
if(nGate == 0) Q <= ~nD;
else Q <= Q;

specify
specparam tRise_nGate_Q = 0.15, tFall_nGate_Q = 0.2;
(negedge nGate *> (Q+:nD)) = (tRise_nGate_Q, tFall_nGate_Q);
endspecify

endmodule

Where is my mistake ?

Thanks,

Pavel.

Title: Re: cannot filter out short pulses
Post by Marq Kole on Aug 3^rd, 2010, 7:17am

You might want to have a look at the PATHPULSE$ specparam (section 14.6.1 of the 1364-2005 IEEE Verilog LRM) which explains how to filter out short pulses with the specify block.

Cheers,
Marq

Title: Re: cannot filter out short pulses
Post by Ken Kundert on Aug 3^rd, 2010, 10:37am

I tend to use the inertial delay of the continuous assignment statement to filter out short pulses. You might want to try that.

-Ken