Node - backdrive a node... 

> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of gacrowell
> Sent: Thursday, July 19, 2007 8:49 AM
> To: piclist@mit.edu
> Subject: RE: [EE][ARM] Pullups
> 
> Three.  There are three good reasons to include resistors in
> pull-up/pull-down lines.
> 
> Third, if the board is to be tested via ATE equipment, the test
> programmer will often want to backdrive a note - cannot do if 
> it's on a
> rail.
> 
> Gary 
> 
> 
> 
> > > There are two good reasons to include resistors in 
> > pull-up/pull-down lines.
> > >
> > > First, if the lines are programmable to be either inputs or 
> > outputs, a
> > > resistor prevents high current from flowing in the event 
> > software bugs
> > > cause the pin to be, say, output high while you tied it to 
> > hard ground.
> > >
> > > Second, it allows you to change your mind later.  Want to 
> > use that pin?
> > > Just remove the resistor from Vcc or ground and you have a 
> > floating pin
> > > you can do what you like with.
> > >
> > >
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