Peter Onion wrote:
> Resent with a TAG this time...
> 
> I'm building a PIC circuit to interface to a very old computer that uses
> 0v for "1" and -10V for "0".
> (http://www.youtube.com/watch?v=8EKBNfm5B4U)
> 
> It will make for simpler interface circuits if I run the PIC from 0V and
> -5V.  (I.E. 0V on Vcc pins and -5V on Gnd pins).   
> 
> Are there any issues with doing this ?  
> 
> PeterO
> 
> 

All voltages are rellative.

The PIC doesn't "know" that what it sees
as "5V" is called by you as "0V".

You could use 15V as "GND" and 20V as "5V" as
long as you do not do anything else "funny" with
your interfaces...
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