Re: gEDA-user: Slots, Swaps and BSDL files

[John Doty <jpd@xxxxxxxxx>]

On Jan 8, 2010, at 10:18 AM, Dave N6NZ wrote:

>
> On Jan 8, 2010, at 8:57 AM, John Eaton wrote:
>
>>
>>> Pinlabel is for humans, and for hierarchy. Pinseq is a unique
>>> numerical identifier for the "pin", independent of the footprint if
>>> any (not all symbols correspond to parts with footprints).
>>>
>>   So slotting lets the PCB designer exchange one 2 input Nand gate  
>> for
>>   another in the same or different package.
>
> Among other things.  I use it to split up complex parts into  
> multiple symbols, for instance power and other infrastructure on  
> its own symbol that can go on the relevant page.

You don't need slotting for that. Just have multiple symbols with  
same refdes.

>
>> Swapping lets them swap
>>   the two inputs pins. How does the pinseq number do both at the same
>>   time?
>
> It doesn't.  Swapping pins isn't really supported.

slotdef attributes are really a general pin mapping mechanism, so you  
can specify pin swaps by having every permutation as a "slot" in the  
symbol (DJ apparently uses this technique). Or, you can attach a  
customized slotdef= attribute to an instance and change the mapping  
to whatever you want.

>   DJ proposed a new mechanism in the "Blue Sky" document.

The biggest problem with the existing mechanism is that it gets in  
the way of reuse. Layout-specific data like pin and slot assignments  
does not belong in reusable source schematics. It also doesn't play  
well with hierarchy, as a slotted components cannot cannot be shared  
between blocks, and power arrangements cannot be separated from the  
signal flow in a hierarchical schematic.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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