gEDA-dev: VHDL Interchange

[al davis]

On Wednesday 28 March 2007 00:12, Sandy Thom wrote:
> Al,
>
> I have been intrigued by your suggestions for a VHDL
> interchange format. The following is an attempt to convey the
> idea at a conceptual level for gschem schematics. I would
> really appreciate your guidance.
>
> gschem				VHDL
> -------------------------------------------------------------
>----------- Design* 	---->		Self contained top level entity
> with a structural architecture describing
> 				the interconnection of schematics.
>
> Schematic	---->		Entity with ports being electrical
> 				connections to other schematics. Version
> 				number and other top level attributes
> 				expressed as vhdl attributes.
> 				Structural architecture with component
> 				instantiations and interconnections.

Yes.

> Components	---->		Entity with ports being the terminals
> 				of the device. Attributes expressed as
> 				vhdl attributes. Behavioural
> 				architecture describing component for
> 				simulation.

Yes.  The Behavioural architecture is supplied by a separate 
library, so it is not needed unless you want to simulate.

> Symbols		---->		How to best describe the relationship
> 				between the component and its symbol?

Symbols are another architecture.

> Nets		---->		Intuitively I want to describe nets as
> 				vhdl signals. It may be necessary to
> 				describe a net as a design entity and
> 				instantiate as a component.

No.  Nets are like components, so they can carry placement info.  
The architecture for simulation is a direct connection between 
ports.


The intent is a simple syntax translation.  Nothing more.

As I look at it more, it seems more likely to use Verilog than 
VHDL.  I have had some discussions with Verilog people about 
how to deal with the entity/architecture concept, and I have 
some ideas.  Nothing final yet.

I am thinking the translators could be written as gnucap 
language plugins.  A common wrapper will use two language 
plugins, one to read, one to write.  Just read and write.  Add 
another hook to process, and it is a nice framework for general 
translation.  The reason for having the intermediate format is 
to allow multiple architectures to be stored together.