VHDL-AMS ,This circuit exhibits singularity

[Steffen Netz]

Hello,

I'm experimenting with VHDL-AMS, and didn't find any News-Group
related to VHDL-AMS.

I'm working with AdvanceMS and often experience the message:
This circuit exhibits singularity ...

Is there any tool to help to debug this errors? I know about
the Trouble-Guide in the Documentation ( two current sources in
parallel, open nodes and so on), but in most cases, the problem
is not as easy as in the docs.

My current problem is the model from the Tutorial from the
36th Design Automation Conference New Orleans, June 21-25, 1999
by ( E.Christen, K.Bakalar ...)


entity Feder is
end entity Feder;

architecture analog of Feder is
quantity x1 : displacement := 0.0;
quantity x2 : displacement := 0.0;
quantity xs : displacement := 0.0;
quantity energy : real;
constant m1, m2 : real := 1.6605655e-24;
constant f : real := 496183.3;
begin
x1'dot'dot == -f * (x1 - x2) / m1;
x2'dot'dot == -f * (x2 - x1) / m2;
xs == (m1*x1 + m2*x2)/(m1+m2);
energy == 0.5*(m1*x1'dot**2 + m2*x2'dot**2 + f*(x1-x2)**2);


end architecture analog;

The Error:
# --> Partitioning circuit...
# Warning 49: This circuit exhibits singularity, due to X2
#
# (See documentation for more detail on singularities)

Any idea?

Thanks in advance,

Steffen Netz

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