Re: gEDA-user: 74xx series

[Stephen Meier <smeier@AlchemyResearch.com>]

1) Implicit connections are good when they help minimize the crowding of 
a schematic.

2) Others who then look at the schematic often ask where is the power 
and ground (not for ttl since it allways found on the same spot for 
conventionally shapped chips)

3) Implict connections are bad for high speed analog where you want to 
filter the devices power from the boards power.

                                      _______
               L1                 |
                                    |
 +5V   -/\/\/\/\/\------------|  Vcc
                        __|__    |
                 C1   __ __   |
                            |
                         Gnd


Steve Meier


Magnus Danielson wrote:

> From: Dan McMahill <dan@mcmahill.net>
> Subject: Re: gEDA-user: 74xx series
> Date: Thu, 24 Jun 2004 20:53:16 -0400
> Message-ID: <20040625005316.GA3237@bondage.mcmahill.net>
>
> Dan,
>
>  
> > On Fri, Jun 25, 2004 at 02:47:48AM +0200, Paul Surgeon wrote:
> >    
> > > How does one wire up the power on the 74xx series of chips in gschem?
> > > There are no power pins on these logic ICs.
> > >      
> > see http://www.geda.seul.org/docs/20040111/netattrib/index.html
> >
> > personally I think implicit connections are EVIL, but that is
> > a religous war.
> >    
> They are not only evil, but they are becoming "A really bad thing" now that we
> have chips with core voltage, various different IO-voltages and where important
> system properties is decided on this. Also, even for the same voltage each
> power-pin may require special care just as much as the signal-carrying pins.
>
> I think it should be phased out as the main principle, but for some designs
> you may still consider it usefull.
>
> Cheers,
> Magnus
>
>