Re: gEDA-dev: SoC: Gerber, DRC, gsch2pcb and D-BUS

[Mike Jarabek <mjarabek-at-NOSPAMsentex_dot_ca>]

(Sorry for the double post, if the first one gets through)

Hi,

Quoting al davis <ad136@freeelectron.net>:

> The existing netlister does not work very well.  I just tried a 
> test case, to see the status now ...  I made a reasonable 
> schematic, and tried all 4 relevant netlisters. (vhdl, verilog, 
> spice, spice-sdb) None gave an output that was directly usable.  
> All of them were missing critical information that is in the 
> schematic.

Because you mention the Verilog netlister, my interest has been peaked.  What 
is missing from the netlist that makes it unusable?  I know for a fact that it 
has been used in several designs to construct synthesizable netlists that 
implement designs. (One of my own, and one that had something like 30 pages of 
schematics that were hierarchichal, which was done by another team.)

If you mean that the descriptions for the implementations for say, TTL gates 
are missing, then I will point out that the netlister is capable of generating 
the appropriate verilog structural gate descriptions.  If you want more 
functionality then you have to provide the models needed.  Let me add that 
what we do is no less than what the $$$ CAD tools do, I have used a few of 
them.  To perform a functional simulation of a design you either need to 
purchase a library of functional simulation models for the chips, or write 
your own. (You can of course use the RTL from any ASIC or FPGA that you have 
designed yourself.)  The decision to select/write the models comes down to a 
matter of trust. (Do you trust the Vendor or your own code more?)

I certainly agree that the Verilog output is not 'lossless' in the sense that 
you can't re-generate the schematic from the netlist.  The truth is, the 
output of the netlister is just that, a netlist.  In this case, it's only an 
interchange format for the interconnect, nothing more.

Please let me know what is missing from the Verilog output that makes it 
unusable.  If it can't be done other ways, I can add it to the netlister.

Thanks,
Mike Jarabek



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