Quote Originally Posted by mister_e View Post
depending of the baudrate i guess. But to me bellow 1-2 % is good.
Thats what I figured.

You could even use a Synchronous serial comm to make it 100% (hum hum) reliable... but the down side is that it use more i/o.
Cant do that because I am already using all the pins on the 452. Some are shared for LCD/Databus. Also the serial port on the 452 is shared amongst several input streams.

Anyways, why don't use the same crystal speed (appart of the PSU current, EMI etc)?
I may well do in this instance for the comms described above but some devices that this will communicate with are already in use and run at 4MHz 9600 baud but messages are very short, typically a single byte.