Oleg,

I write 90% of my programs in assembler, so the time penalty is no more than 10-20 uSec. I also use the serial port in some of my applications, but you can still debug, even though it is used in your application, most of the time I am getting the value of the accumulator to see the value of a variable or to see what the value of the accumulator is before a conditional jump. The test is taken out after the problem is fixed. I suppose that you could also have two different baud rates, one for the application and another for debugging. Anyway to each his own as I always say, there is no right or wrong way to troubleshoot as long as you solve the problem.

Jacob