Serial Port

Introduction

A Serial Port is the generic term for a port on a computer that can be connected to other devices. This may be a proprietary connector with a few wires in it; an AppleBus/AppleTalk connector to connect a printer, modem or another computer; or even an Ethernet port. But by far the most common usage is for an RS-232 port with a 9-pin D-connector (DE-9) for asynchronous communications (see Communications). All these ports have one thing in common: the data is sent over a small number of wires (usually one in each direction) in serial fashion, rather than all at once in parallel.

But since "Serial Port" is usually used to refer to the COM Port that is found on the PC (to distinguish it from the rarely-seen-nowadays "Parallel Port"), this page will concentrate on that. Refer to the specific pages for other port types. This page will cover the physical port itself, its signals and how they're commonly used, and the most common protocol used on this port.