Re: gEDA-user: Support for heterogeneous symbols?

[msokolov@xxxxxxxxxxxxxxx (Michael Sokolov)]

fricker <fricker@xxxxxxxxx> wrote:

> I am evaluating gEDA and came across one feature I am extensively  
> using today with a commercial EDA tool when dealing with large  
> components, like SOC, FPGAs and ASICs: heterogeneous symbols.
>
> I searched the doc, the mailing lists and the Web but could not find  
> how I could create and use such symbols with gschem and gnetlist.

Ah yes, as the mailing list archives can attest, this was also one of my
first questions when I started using gEDA!  (No, I've never used any
commercial EDA tools because I refuse to use Weendoze or Solaris or
whatever other proprietary OS they require, but I've entered the HW eng
field from a software background after watching the HW engs I was
working with and wanting to do that too.  As my work has always been
with large microprocessor-based systems, all schematics I've ever seen
(for very complex microprocessor-based boards) use lots of heterogeneous
symbols.)

> Does gschem support such a way to deal with large devices?

Yes.  The schematics for the SDSL board that I've just captured and
getting ready to lay out make heavy use of heterogeneous symbols.  The
MC68302 microprocessor is split into 3 symbols, the SDSL transceiver
into 5, and the FLEX10K FPGA also into 5.

> If the answer is yes, then how?

Make separate and independent symbols.  Each symbol would cover a
subset of the device pins, and each pin would have its correct number,
so when this is done right each pin number will appear in exactly one of
the symbols.  Instantiate all these symbols on your schematic (can be
on the same page or different pages of a multipage non-hierarchical
schematic, the kind I'm used to) and give the same attributes,
particularly the refdes (and the footprint if you attach it at the
schematic level rather than in the symbol) to all symbol instances
describing parts of the same physical component.

HTH and welcome to Free EDA!

MS


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