[Magic-dev] RE: Broken nets

[R. Timothy Edwards]

Dear Satpal,

> I recently downloaded Magic 7.1 and am using the tech file
> SCN3ME_SUBM.30.tech27 to design for AMI 0.5 um process. On extraction
> (ext all) and running ext2spice to generate a netlist, I occasionally
> (not always) find that a single net in the layout has been broken
> into 2 different nets in the spice file, this leads to the failure of
> simulation.

There are a number of reasons this sort of thing can occur.  The
reason that they seem "random" is that the extractor is not to
blame---the extraction algorithm in magic is surprisingly robust---
but there are a number of other subtle errors that can occur.

One of them, which may have caused at least one of your broken
simulations, is that labels can get copied from one cell into another,
and end up on separate layer types (e.g., metal1 and metal2) that
are not connected.  Extraction will short nets having the same
(labeled) name.

Usually it is a good idea to ensure that the circuit layout is correct
by doing LVS (layout vs. schematic) as well as extraction+simulation.


					Regards,
					Tim