tito-t:
sorry, but IMO your answer is ambiguous and vague. My cpus are 16MHz AVR (e.g., Nano, Uno or Mega 2560), and as already stated, Zero (M0), Due (M3), and esp8266.
It has just occurred to me to ask if your questions in this Thread have been prompted because you have been having trouble getting communication to work reliably?
If so you need to post the program that illustrates the problem.
...R