Hi, >I tried to communicate with PC. :-) >It's a very simple serial communication source. Just to make sure there's no misunderstanding... The cc65 package comes with a ready-to-use dynamically (or statically) loadable SSC driver, that supports hardware flow control and uses interrupts to drive a 256 byte ring buffer. http://www.cc65.org/doc/apple2-7.html#ss7.5 Regards, Oliver