I'm trying to take a USB signal and convert it so that the ATXmega256A can take the data in via usart. I'm trying to use the FT232R for this. The FT232R has RX, TX, RTS, CTS, and a clock that need to be connected... the usart on the xmega has only tx, rx, and xclk... missing cts and rts.
Essential to what? Using software flow control you can run a bidirectional serial line using only 1 signal line and ground, typical serial setups use two and ground, one for TX and one for RX so you have a full duplex link, makes flow control easier to manage.. The hardware flow control and other signal lines are really only a throwback to older hardware that used these control signals to determine device function and control like modems and old dumb terminals, they're not strictly speaking needed for anything. They exist on just about all standard serial ports though so they can be useful for other functions if you'd like, they make nice general purpose I/O lines and with proper polling can be used as a short byte parallel port.