Re: MUX2?

[Tuukka Toivonen]

On 17 Aug 2001, Al Arduengo wrote:

> I sure hope this is not a faq. I searched the docs I have but could

Well, I had the same problem.

> 2->1 mux. I connected two inputs, an output and a select. When I try to
> run a simulation on the whole contraption, I get an error in the
> message window reporting that MUX2 is an unknown model. I inspected

You can create almost any component in the digital schematic editor,
such as 10-input XOR or something, but a simulator will simulate only
those components that it understand.

The internal ALS simulator doesn't understand except a few basic
components.

Some external simulator might support even less: for example, the
IRSIM simulator supports only pMOS, nMOS and depletion transistors.

Now, what to do? I suggest that you would create your own library
that contains all the basic components you use. For example, create
Library "mylib" and into that Cell "my_mux2". Create also Icon for the
Cell, for that you can use the Digital Component Panel (select from
"Change Current Technology"). I attached an example in this mail, read
it with "File/Import/Readable Dump".

Another way, if you're using ALS, is to define yourself the behaviour
of "mux2". This is explained in Electric's manual, Chapter X: SIMULATION
/ 4: Behavioral Models. But I think the first way is easier and better.
You might need also to mess with "VHDL Compiler/Select Behavioural
Library" if it doesn't work otherwise.

> Strangely, for some time an xnor2 I used was also complained about 
> just like the mux2 but now, after recompiling electric, it seems to 
> be acceptable in the vhdl view.

Check that the simulation gives correct results! Sometimes Electric
might use some old VHDL when the VHDL generation fails. You'd better
to use Delete Facet... command to delete all automatically generated
VHDL- and ALS- type facets of the Cell that you want to simulate.
That way, if the VHDL generation fails, the simulation can't
use any old VHDL.

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