PC Serial Ports
Background
Serial ports (also sometimes referred to as communications ports or COM ports) are hardware interfaces that permit your PC's microprocessor to communicate with peripheral devices using a communications standard called
Under DOS (and Windows, which works cooperatively with DOS), the serial port interfaces in a PC are uniquely identified by specific device names: COM1 (“serial communications port 1”), COM2 (“serial communications port 2”), and so on, usually up through COM4. A particular PC might have none of these devices, some of them, or all of them installed. For example, most PCs currently on the market arrive from the manufacturer with two serial ports already installed (COM1 and COM2), often integrated onto the computer's main system board. Installing additional serial ports (for example, COM3 or COM4) is usually accomplished by purchasing an
For most purposes (such as configuring software), the generic description of serial ports provided by their device names is sufficient. For example, during the PassageWay Service Provider installation procedure, you are asked to provide the device name of the serial port to which you have connected the telephone (for example, COM2). Unfortunately, this abstract view of serial ports is not sufficient for other purposes, notably for troubleshooting problems: To be able to do this effectively, a basic understanding of serial port hardware is required. In particular, it is essential to understand the mechanics by which the computer's microprocessor communicates with serial port hardware.
