Re: disallow distributed switch branches

Kevin Cameron wrote:
> 
> > The reason for having OOMR voltage contributions being in series is
> > consistency with the rest of the language. Why should the rules be
> > different for out-of-module-references than for in-module-references?
> >
> I think you are just avoiding my question on justifying the behavior
> being different depending on how you wire things up. I'd ask the
> question: why should in-module behavior be different from multi-module
> behavior, and hence why should OOMR behavior be different from that.

In-module behavior is already different from multi-module behavior:

module A(a,b);
  inout a,b;
  electrical a,b;
  analog begin
    V(a,b) <+ 5.0;
    V(a,b) <+ 6.0;
  end
endmodule

module B(a,b);
  inout a,b;
  electrical a,b;
  vsine #(.dc(5)) v1 (a,b);
  vsine #(.dc(6)) v2 (a,b);
endmodule

Whether module B can be simulated in a particular simulator is beside the point. (Ken and I will avoid simuluators that allow it, because we think it's a bad idea; you will use them, so you can model parallel switches.)  You get 11 for A and something else (an error, 5.5, ...?) for B.

Bear with me a little on this example:

module base(a,b);
  inout a,b;
  electrical a,b;
  branch (a,b) Ibr;
  analog I(Ibr) <+ 5.0;
endmodule

module augmentor();
  analog I(top.mybase.Ibr) <+ 6.0;
endmodule

module iprobe();
  analog $strobe("I = ", I(top.mybase.Ibr));
endmodule

module top();
  electrical n1;
  ground gnd;
  resistor #(.r(1k)) R1(n1, gnd);
  base mybase(n1, gnd);
  augmentor aug1;
  iprobe probe1;
endmodule

The OOMR probe in iprobe really must be sensing the current in that branch "Ibr"; it would be non-sensical for the probe to somehow create a new branch in parallel and sense that (zero) current.  Hence, the OOMR contribution in augmentor *must* add 6.0 to the 5.0 already on branch "Ibr" in instance mybase module base, not create a new branch in parallel for the contribution.  Here we had no problems with v-sources in parallel.  

Now let's switch all the I's to V's (access functions and Ibr->Vbr).  Again, I would maintain, the augmentor adds 6.0 to the 5.0 already on Vbr, and the $strobe prints V = 11.0.


In an earlier message, you (Kev) wrote:

> Contributions from analog blocks in different modules are in parallel 
> for potential and flow - thats the way it has always been. I'm just 
> asking for that behavior to apply consistently.

and I'm saying these contributions are *not* in parallel.

-Geoffrey

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