An asynchronous UART (serial port) is common on many microcontrollers, and provides a simple way for two devices to communicate without having to match system clock rates. This application note describes how to implement a 10-bit asynchronous UART in software on the MAXQ3210 microcontroller using two standard port pins. This simple modification allows the serial port to communicate over RS-232 and RS-485 networks, or to connect to a PC COM port.