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Design Languages >> Verilog-AMS >> help for this special model
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Message started by fencl_xu on Jan 21^st, 2010, 8:53pm

Title: help for this special model
Post by fencl_xu on Jan 21^st, 2010, 8:53pm

Hi,all
Firts, i'm a newer in verilog-a and this forum.
i need a special model used in hspice, that a delay cell for ckout from ckin,i have constant delay model as follow,but actually i need is delay time----dtime,can control vs time when used in hspice,such as .tran in hspice,when t=t1 dtime=20n,t1-->t2 ,dtime vary from 20n to 30n lineraly. how should i do ?
`include “discipline.h”
module delay_cell (in, out);
input in;
output out;
electrical in, out;
parameter real dtime = 20n;

analog begin
V(out) <+ delay(V(in), dtime);
end
endmodule

need help sincerely and urgent for project reason :'(.

Title: Re: help for this special model
Post by Geoffrey_Coram on Jan 22^nd, 2010, 5:42am

`include “discipline.h”
module delay_cell (in, out);
input in;
output out;
electrical in, out;
parameter real dtime1 = 20n from (0:inf);
parameter real dtime2 = 30n from (dtime1:inf); // dtime2 > dtime1
parameter real t1 = 1n from (0:inf);
parameter real t2 = 5n from (t1:inf); // t2 > t1
real deff;

analog begin
if ($abstime < t1)
deff = dtime1;
else if ($abstime > t2)
deff = dtime2;
else
deff = dtime1 + ($abstime -t1) * (dtime2-dtime1)/(t2-t1);

V(out) <+ $absdelay(V(in), deff, dtime2);
end
endmodule