I have tried to use the ftdi and maxim chip sharing the same TX and RX pins on a ATMEGA644P. It seems they both are able to transmit(uC sends data to computer), but only the MAX232 can receive (computer sends data to uC). I think I might have an idea why this is. The pins of the chips connected to the atmega's TX pin are inputs. That means the uC can drive them high or low no problem. But the pins of the chips connected to the atmega's RX pin are outputs. This means that when one chip tries to drive the atmega's RX pin high or low, it also must drive the other chip's output high or low. The MAX232 can handle this and the FT232R can't? Just an idea. Any suggestions?