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Simulators >> AMS Simulators >> $rdist_xxx not supported outside the analog block in AMS Designer
https://designers-guide.org/forum/YaBB.pl?num=1318150379

Message started by ywguo on Oct 9^th, 2011, 12:52am

Title: $rdist_xxx not supported outside the analog block in AMS Designer
Post by ywguo on Oct 9^th, 2011, 12:52am

Hi Guys,

I have verilog-AMS code as below. I want to have random variation for cap15.

Code:

� parameter real c15 = 5.12p from (0:inf);
�real cap15, ....
� initial begin
� � cap15 = ($rdist_normal(1,0,1)*0.001*sqrt(2^10)+1)*c15;
� end

However it stops in elaboration and reports

Quote:

� �Elaborating the design hierarchy:
ncelab: *N,SFEDPL: Deploying new SFE in analog engine.
�Discipline resolution Pass...
�Building instance overlay tables: ................
� cap15 = ($rdist_normal(1,0,1)*0.001*sqrt(2^10)+1)*c15;
|
ncelab: *E,EXNOSUP (./dac.vams,38|24): In AMS Designer, the shown system function is not supported outside the analog block.
.... Done
ncverilog: *E,ELBERR: Error during elaboration (status 1), exiting.

Unfortunately, AMS designer does not compatible with Verilog-AMS LRM version 2.3 fully. What can I do?

Thanks
Yawei

Title: Re: $rdist_xxx not supported outside the analog block in AMS Designer
Post by boe on Oct 10^th, 2011, 1:28am

Hi Ywguo,

I'd try the initial_step event.

B O E

Title: Re: $rdist_xxx not supported outside the analog block in AMS Designer
Post by Ken Kundert on Oct 10^th, 2011, 8:38am

Try $dist_normal(). I think that is the name used in the digital context.

-Ken

Title: Re: $rdist_xxx not supported outside the analog block in AMS Designer
Post by boe on Oct 10^th, 2011, 9:37am

Hi,
The documentation clearly states that $rdist_xxx is not supported in digital contexts.

Quote:

Try $dist_normal(). I think that is the name used in the digital context.

However, according to the documentation nowadays it generates integers.

B O E

Title: Re: $rdist_xxx not supported outside the analog block in AMS Designer
Post by Geoffrey_Coram on Nov 4^th, 2011, 4:24am

Can't you re-scale the integers from $dist_normal (divide by the largest) and get something close to what you want?