RS-422 is basically just higher-speed RS-232. It can be programmed just like RS-232 for basic serial communication.

The two big differences are in speed, and speed control. A 16550 UART on the PC side provides a 115,000 bps serial connection over RS-232. The RS-422 on a Mac is capable of double that, 230,000 bps, natively. However, the port can be 'externally clocked', so that a device can increase the clock even above that. Apple's serial networking protocol, "LocalTalk" could be externally clocked up to 2 Mbps!