The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Modeling >> Behavioral Models >> [SOLVED] oneshot circuit or monostable multivibrator
https://designers-guide.org/forum/YaBB.pl?num=1475177011

Message started by Shahriar on Sep 29^th, 2016, 12:23pm

Title: [SOLVED] oneshot circuit or monostable multivibrator
Post by Shahriar on Sep 29^th, 2016, 12:23pm

Hi,

I'm new to veriloga. I'm trying to make a veriloga model for a one-shot circuit. The steady output will be low. It would trigger on both positive and negative edges of input and the output will stay high for a defined "pw" parameter.

I can't figure out how to code the output getting back to steady state after "pw" time has passed after an edge occurs in input.

Here's the code I've written so far.

Code:

// VerilogA for scratch_veriloga, oneshot, veriloga

`include "constants.vams"
`include "disciplines.vams"

module oneshot (trigger, oneshot);

input trigger;
output oneshot;
voltage trigger, oneshot;

parameter real vil = 0.5;
parameter real vih = 2;
parameter real thres = (vil+vih)/2;
parameter real vol = 0;
parameter real voh = 2.5;

parameter real td = 0.1n from [0:inf);
parameter real tt = 0.1n from [0:inf);
parameter real pw = 3u from [0:inf);
//parameter integer dir = +1 from [-1:+1] exclude 0;

real state;

analog begin

@(cross(V(trigger)-thres)) state = 1;

//can't figure out how to code that 'state' will go back to 0 after 'pw' time after cross event.

V(oneshot) <+ transition(state?voh:vol,td,tt);

end

endmodule

Could anyone please tell me how I can do this? Or point me to an example?

Thanks.

Title: Re: oneshot circuit or monostable multivibrator
Post by Shahriar on Sep 30^th, 2016, 10:56am

Found the solution myself here. http://www.designers-guide.org/Forum/YaBB.pl?num=1210828245

Code:

@(cross(V(trigger)-thres)) begin
state = 1;
next = $abstime + pw;
end
@(timer(next)) state = 0;

Title: Re: [SOLVED] oneshot circuit or monostable multivibrator
Post by Ken Kundert on Oct 1^st, 2016, 6:00pm

Thanks for posting your solution.

-Ken