Re: VAMS-CM: new LRM draft, DAC meeting

[forgot to send this to the reflector]

Geoffrey.Coram wrote:

>Kevin -
>
>
>Kevin Cameron wrote:
>
>
>>Surely you would only disinherit the 2 (l & w) if the rest are shared? - you only need
>>to remember the overrides on the inheritance path.
>>
>>
>
>
>I think you're not quite following the concept. Think model card
>in Spice. (I also have a lot of work to do on putting examples
>in the LRM draft.)
>
>Suppose I have the following:
>
> module bsim6 (d,g,s,b);
> inout electrical d,g,s,b;
> parameter l, w, vth0, tox, vfb, kp, nsub, ... // 600 of these
> (*desc = "transconductance"*) real gm;
> (*desc = "gate-source capacitance"*) real cgs;
> ...
> endmodule
>
>Now, I want to set up a way to access this module in such a way
>that the paramset/macromodule sets the values of the "process
>specific" parameters vth0, tox, etc., and the user can only
>specify l and w. Also, I want gm and cgs to be available.
>
>I will have
>
> paramset nch bsim6; // standard nmos
> parameter l, w;
> .tox = 10n; .vth0=1.0; //etc.
> endparamset
>
> paramset nch5v bsim6; // 5volt nmos
> parameter l, w;
> .tox = 20n; .vth0=2.0; //etc.
> endparamset
>
>and maybe I have several paramsets with each name, for binning.
>Now, my instance line looks like this:
>
> nch #(.l(.1u), .w(10u)) M1(d,g,s,b)
>
>and I am not able to override tox on the instance line, because
>it is not a parameter for the paramset nch.
>
>
>-Geoffrey
>
No reason we can't do that, I'd probably go for:

    macromodule nch const interface bsim6;
        parameter l, w; // override const for l & w
        bsim6 #(.tox(20n),.vth(1.0),.*) (.*);
    endmodule

BTW ".*" only works for ports in SV - but I see no reason for not using
it for parameters too
(and it should be less error-prone with the inheritance).

Another thing I might want to do is inheritance and extension e.g.:

    macromodule nmos_sub interface nmos (inout sub); // inherit from
primitive and add a substrate port
        ntran_sub #(.*) (.*);
    endmodule

That way in mixed-signal I can tell a 4-port device is a transistor with
an extra port I can
ignore if I'm only doing digital - no-need to re-netlist.

Kev.
Received on Fri Jun 18 09:02:15 2004