A serial bus - for the purpose of this discussion is a serial, multidropped bus communication system that interfaces with a PC or a master device's serial port and employes an asynchronous byte orientated frame format. When computers became commonplace, these serial communication systems were adopted using I/O devices called serial ports (or COM ports on PC's) that uses the UART chip.

Serial busses are commonplace in industrial control networks where they are very often used to communicate with field devices such as controllers, RTUs and PLCs using an application level messaging format such as Modbus or DNP3.