serial communication time

[mister_e]

Then throw that book away

HSERIN is one, method. Reading the USART register is another one, using it's interrupt is a third one.

Now you have to determine which process is much important. If you really have a need for speed for your interrupt, you may need to switch to Darrel's Instant-Interrupt. Not enough? ... use ASM interrupts.

@10MHz, you could use a 57600 baud communication without too much problem.

Not sure of your whole requirement... but i would use USART interrupt for that... i'll read it again.. just to make sure i didn't miss the main idea.