Chaipi Wijnbergen wrote:
>
> Hello PIC experts,
>
> I am developing a small project using the PIC 16C74 and recently needed
> to change the Crystal from 16MHz to 20MHz. When I did that, a problem
> started with the asynchronous communication controller, it started to
> recived wronge characters.

  I have had similar problems.  Two different systems (both based on the '74)
 with two different
boards (this does not appear to be a board level problem) both running at 20MHz.
  These systems
were driven by a PC that sent down a sequence of commands and the PIC based
 boards fed back
status information so error handling in the PC program handled 'cleaning up' the
 communications
errors.  Spent quite a bit of time trying to figure out what was wrong and it
 appeared that the
PICs were to blame.

- John Miskimins