Serial port and its relevance

Now, to hear the expression "computer ports", you do not need to go to specialized stores or to own computer equipment. Even the students of the junior classes are well versed in this matter.

At the words "port" a person usually has a dock with high cranes, where large ships go, delivering products and loading goods. In computer technology, the input-output port is one of the types of hardware interface intended for connecting internal and peripheral devices to the data bus of the motherboard. Since the advent of the first computers, a large number of different ports have been proposed, differing both in physical implementation and in the protocol used. Some have survived and are used even in our time. So, serial port many motherboard manufacturers began to unzip again on their products.

Why is it so remarkable? Asynchronous serial port (sometimes called COM, from the English word "Communications") appeared in the first IBM-compatible models of the computer. It was used to connect a mouse, modem, other peripherals and organize the simplest network connection of two computers (a null modem cable was required). One of the advantages of having a serial port is the simplicity of hardware and software implementation.

Physically it is represented by a 9 or 25 pin connector. Data transmission in it occurs bit by bit, sequentially (by the way, from here the second name has occurred). The protocol does not impose any time-frames to the gap between every 16 bits (2 bytes). Due to this feature, the serial port is sometimes called asynchronous.

It is worth noting that the bit rate of information is still regulated. For example, the standard hardware implementation allows a speed of 115 200 bits per second (baud), although Windows operating systems usually artificially limit it to 9600 (the user can make adjustments in the device manager). Unlike other serial interfaces (USB, FireWire), bits are not collected in packets, but are transmitted as they arrive.

A widespread USB interface was introduced to expel an aging COM port (RS-232C) from the market. This step was inevitable, since the data transfer rate in the most productive version was only 921600 baud, which was not enough (compare with USB and its 480 MB / s). The second significant drawback is the impossibility of a hot-pluggable connection: attempting to connect the device to a serial port with a working computer resulted in the impossibility of work at best due to the lack of Plug & Play technology, and at worst - to failure of both the device itself and the controller COM port on the motherboard (expansion board).

Because of this, a few years ago all the cards that were released did not have a COM port, as it happened with PS / 2 and AGP. However, a large number of existing peripherals, designed to work with the serial port, forced manufacturers to return COM and even LPT (parallel). No doubt, many users have told them "thank you". After all, to reconfigure the satellite receiver, you do not need to search for an old computer or buy unsuitable adapters-inverters. In addition, most programmers also work through the serial port, since writing control programs for it does not cause any special difficulties.

Interestingly, many modern peripherals for correct operation in the operating system emulate their COM port. These are mobile phones, radio modems, Bluetooth adapters , etc. Of course, the characteristics of such a virtual port far exceed the standard implementation.