OK, I've got a 89C2051 UART Tx pin shifting out bytes at 9600-8-N-1 and I just want to know if I can tie that pin directly to a '2313 UART Rx pin? I only need half duplex. I'd like to know if the hi/low levels are compatible pin to pin. Both chips will be tied to the same Vcc=5 volts. I tried reading the Atmel 8051 hardware manual, and well, yuck it's hard to figure out things as compared to how well we've got it in AVR land.