I dowloaded AVRStudio from Atmel web site and I wrote a simple program that uses the UART, implemented on a AT90S8535 system. I tried to simulate my program: I created a stimuli file performing the serial bit flow, but the processor didn't serve the UART receive interrupt routine. Then I tried to manually change the rx bit on pind register of the simulator with the correct timing, but the behaviour was the same. It's not a software error, because the program runs well when I try to work with the part on my system. I followed the explanation provided with the on line help, to create the stimuli file, but it doesn't work: is there something else I can try?
Thank you to those who want to answer.