Now to hear the expression "computer ports", you do not need to go to specialized stores or own computer equipment. After all, even primary school students are well versed in this issue.
At the words “port”, a person usually sees a pier with high cranes, where large ships enter, delivering products and loading goods. In computer technology, the input / output port is one of the types of hardware interface designed to connect 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 in both physical implementation and the protocol used. Some are preserved and are used even in our time. So, many motherboard manufacturers began to unsolder the serial port again on their products.
Why is he so remarkable? Asynchronous serial port (sometimes called COM, from the English word "Communications") appeared in the first IBM-compatible computer models. Used to connect a mouse, modem, other peripheral devices and organize the simplest network connection of two computers (a null modem cable was required). One of the advantages that the serial port has is the simplicity of the 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, the second name came from here). The protocol does not overlap any time frame between every 16 bits (2 bytes). Due to this feature, the serial port is sometimes called asynchronous.
It should be noted that the bit rate of information is still regulated. So, in a standard hardware implementation, a speed of 115,200 bits per second (baud) is allowed, although usually Windows operating systems artificially limit it to 9600 (the user can make an adjustment in the device manager). Unlike other serial interfaces (USB, FireWire), the bits are not collected in packets, but are transmitted as they arrive.
A common USB interface was introduced to push the aging COM port (RS-232C) out of the market. This step was inevitable, since the data transfer rate in the most productive variety 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” connection: an attempt to connect the device to the serial port while the computer was running led at best to inability to work due to the lack of Plug & Play technology, and in the worst case to failure of both the device itself and the controller COM port on the motherboard (expansion board).
Because of this, several years ago, all manufactured boards did not have a COM port, as happened with PS / 2 and AGP. However, a large number of existing peripherals designed to work with a serial port forced manufacturers to return COM and even LPT (parallel) again. No doubt many users said “thank you” to them. After all, to reflash a satellite receiver, you no longer need to look for an old computer or purchase uncomfortable inverter adapters. In addition, most programmers also work through the serial port, since writing control programs for it does not cause any special difficulties.
It is interesting that many modern peripheral devices emulate their COM port for correct operation in the operating system . These are mobile phones, radio modems, Bluetooth adapters , etc. Of course, the characteristics of such a virtual port significantly exceed the standard implementation.