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Modeling >> Behavioral Models >> Pulse source in Verilog-A(MS)
https://designers-guide.org/forum/YaBB.pl?num=1178633356

Message started by nvs117 on May 8^th, 2007, 7:09am

Title: Pulse source in Verilog-A(MS)
Post by nvs117 on May 8^th, 2007, 7:09am

Hi there,

What are the possibilities to model a source which gives a rectangular voltage (or position) pulse at a certain time point?

I have tried this here, but this is doesn't give the right result - it always produces large outputs (either below or greater zero).

BTW: Don't hesitate, this is a signal-flow approach! ;-)

// position pulse

module pos_pulse (out_pos);

parameter real startval = 10.0;
parameter real endval = 0.0;
parameter real period = 100.0;
parameter real starttime = 1.0;
parameter real endtime = 15.0;

output out_pos;
position out_pos;

analog begin

@(initial_step) begin
Pos(out_pos) <+ slew(startval, 1.0e-9, 1.0e-9); // also tried "transition" here
end

@(timer(endtime)) begin
Pos(out_pos) <+ slew(endval, 1.0e-9, 1.0e-9); // also tried "transition" here
end
end
endmodule

Any ideas?

Chris

Title: Re: Pulse source in Verilog-A(MS)
Post by Geoffrey_Coram on May 8^th, 2007, 12:06pm

nvs117 wrote on May 8^th, 2007, 7:09am:

@(initial_step) begin
Pos(out_pos) <+ slew(startval, 1.0e-9, 1.0e-9); // also tried "transition" here
end

I don't think this is legal syntax ... you shouldn't have <+ nor slew inside an event. Instead, you should have a real value that gets set in the events, and the contribution should be performed always:

real outval;
@(initial_step) outval = startval;
@(timer(endtime)) outval = endval;

Pos(out_pos) <+ transition(outval, 1n, 1n);

Title: Re: Pulse source in Verilog-A(MS)
Post by nvs117 on May 9^th, 2007, 3:59am

Hi Geoff,

This works fine.

Thanks from a VAMS newbie.

;-)