Сейчас чтобы услышать выражение «порты computer ", do not need to go to specialized stores or be the owner of computers. Even the students of the lower grades are well versed in this matter.
При словах «порт» человеку обычно представляется 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.
Чем же он так примечателен?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 9 or 25 pinconnector. Data transmission in it occurs bit by bit, sequentially (by the way, from here there was a second name). The protocol does not impose any time frames to the gap between each 16 bits (2 bytes). Due to this feature, the serial port is sometimes called asynchronous.
Стоит отметить, что скорость передачи бит 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 an adjustment in the device manager). Unlike other serial interfaces (USB, FireWire), bits are not collected in packets, but are transmitted as they arrive.
A common USB interface has been introduced withpurpose of expulsion from the market of the aging COM port (RS-232C). 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 major 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 best of all to impossibility of work due to the lack of Plug & Play technology, and at worst to the failure of both the device itself and the controller COM port on the motherboard (expansion board).
Because of this, a few years ago, allthe manufactured boards 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.
It is interesting that many modern peripheraldevices 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.
