Re: gEDA-user: 74xx symbols

[Jim Battle <frustum@pacbell.net>]

At 07:41 AM 7/31/02 -0400, you wrote:
>Hi,
>...
>         I should warn everybody right now, I have finished my changes
>to the standard attributes for symbols.  All of these changes are
>now in CVS.  I have already written two perl scripts which will
>take <=20020527 symbols/schematics and update them to the current
>attribute set.  Gone are the days of pin#=#, slot#=# etc...  These have
>been replaced by pinnumber=#, pinseq=#, slotdef=#:#,#,#....  I have also
>changed a few of the other attributes to be consistant and less arbitrary.
>Details will be made available with the next release.
>
>                                                                 -Ales

Since there is a large change underway, this is a good time to raise this 
suggestion, but then again, maybe it is a bad time since so many things 
have changed already.  It would be easy to augment the library later 
without disrupting current properties, so I guess it could wait.

The suggestion is to have equivalence classes of pins.  This would be 
useful in two situations.  The most obvious is for routing, in order to 
minimize signal crossings.   Likewise, in the schematic editor pin swapping 
in nice to minimize the signal crossings there too.  Of course it would be 
possible to add a command to manually select two signals and then swap 
them, but having the equivalence class information would make it 
easier.  For instance, on the inputs of a 2-input NAND gate you could just 
type the pinswap command and select one of the pins since the pin that it 
needs to be swapped with would be known.  Even more useful is something 
like a 74374 where if you swap two inputs, the corresponding outputs could 
also be swapped.

-----
Jim Battle == frustum@pacbell.net