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Monte carlo on a verilog A custom macro model based on device instance not subckt instance

Fabb over 11 years ago

Hello,

I am developing my own macro model in verilogA

module test1 (p1,p2);

…

endmodule

Then I use a model card approach to manage the parameters and their variations:

simulator lang=spectre

section TT

….

endsection TT

section LL

….

endsection LL

…..

section STAT

parameters _param1=1

parameters _param2=1.1

statistics {

process {

}

mismatch {

vary _param1 dist=gauss std=5 percent=yes

vary _param2 dist=gauss std=13 percent=yes

}

include "modelCard.scs" section=MODEL

endsection STAT

section MODEL

ahdl_include “path/modelTest1.va"

model modelSymbolName test1

+ param1 = _param1

+ param2 = _param2

endsection MODEL

Then I got the following error

Error found by spectre during Monte Carlo analysis `mc1'.

ERROR (SFE-2458): dut Instance 'I5' should be subckt instance not device instance (statement ignored).

With I5 is the instance name of modelSymbolName

Is it means that to run a monte carlo, the model cards must be written with a subckt calling the model itself ?

Regards,

Fabrice

Andrew Beckett over 11 years ago

The "dut" parameter for monte carlo essentially is a way of specifying which instances have monte carlo applied. In general only subckts can have mismatch applied, because the unique parameterization is done per subckt instance rather than primitive instance (for example, see Recommended Spectre Monte Carlo modeling methodology)
Regards,
Andrew.
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