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Design Languages >> Verilog-AMS >> error while simulating using AMS in cadence
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Message started by bharath on Dec 14^th, 2009, 12:15pm

Title: error while simulating using AMS in cadence
Post by bharath on Dec 14^th, 2009, 12:15pm

I have a verilog-ams block of low pass fitler...

analog
begin

V(filt_out) <+ laplace_nd(I(filt_in), {1,r1*c1}, {0, c12 , r1*c1*c2+ r2*c3*c12, r1*r2*c1*c2*c3}) ;

end

i have initialised r1,r2,c1,c2,c12,c3 as real and proper values
when i simulate i get the following error

coefficient of the highest power of `s' filterdenominator is zero.This
error commonly arises if the coefficients are initialized inside an
@initial_step statement that does not account for the analysis during
which this error was reported.

I am new to Verilog-AMS so dont know where i am going qrong ..

Title: Re: error while simulating using AMS in cadence
Post by Geoffrey_Coram on Dec 14^th, 2009, 12:55pm

Try replacing the variables with numbers just to see if the variables aren't being set properly.

I forget: is the first coeff in the denominator the highest power of s or the lowest?

Title: Re: error while simulating using AMS in cadence
Post by bharath on Dec 14^th, 2009, 1:18pm

I will try setting the values instead of variables

the first co-efficient is the lowest power of s -- atleast according to Verilog LRM manual.

Title: Re: error while simulating using AMS in cadence
Post by Peruzzi on Jan 2^nd, 2010, 5:55pm

Bharath,
You can only use constants or parameters as laplace_nd coefficients, not variables. If you must use variables, convert your H(s) into a set of differential or integral equations.
Cheers,
Bob P.
www.RPeruzzi.com