>
> Hmmm... I think that controlling 5V logic with 3V will work OK, but what if
> you need to read something from this 5V device by a 3V PIC? Isn't there a
> chance to blow something (from the datasheets, PIC I/O pins are rated
> to max. Vdd+0.6V)?
>
There are several possibilities:

  1.  Use a level transition phase, such as a transistor, or something.

  2.  Do nothing.  This will work fine, as long as the 5V logic is uses
      TTL _output_ levels, not CMOS levels.

  3.  Use a resistor in between the chips.  This will slow the logic
      down, and increase power consumption.  The PIC acts like a diode
      to the positive rail, if the input is higher than Vdd+0.5V.  As
      long as you don't put too much current into the pin, you should
      be ok.

##########=========================-------------------------------------*
# Darwin Hawes  <hawes@physics.ubc.ca>                                  |
I This is a typical net.posting.  Any resemblance to reality is         I
| strictly coincidental.                                                #
*-------------------------------------=========================##########