Despite the widespread use of Universal Serial Bus (USB) ports, for a number of our customers who use converters, serial ports are still an important interface. Not just on computers, but in addition digital cameras, printing equipment, modems and a wide range of industrial automation network equipment, continue steadily to make use of serial port connectivity. (Although, if you examine computers manufactured within the last couple of years, you'll probably find only one serial port along with, on some models, a parallel port.)
One of the great benefits of serial communications could be the simplicity achieved by taking 8-bit bytes and transmitting them one bit at the same time down a single wire. This helps to keep both cabling costs low and the controlling communications protocol simple. AliBaba Dastaan E Kabul Watch Online Needless to say the trade off is that transmitting 8 bits serially, as opposed to in parallel, is eight times slower! (Remember that parallel ports were developed after serial ports.
Just how do serial communications actually work? Well, although we mentioned the serial transfer of 8 bits on the wire, in fact control bits are also transmitted. A 'start' bit to point data is arriving, a 'stop' bit to point data is completed, and an (optional) parity bit.
The 'electronic brains' behind this data transmission is just a dedicated silicon chip called a 'Universal Asynchronous Receiver/Transmitter' (UART). This chip is a program between the inner computer bus's parallel communications, and the serial ('Com') port. Some UART chips have the ability to cache significant levels of data from the computer bus while simultaneously transmitting onto standard serial ports at rates as high as approx 115 kbps.
The serial port connectors in use today contain 9 or 25 pins, with the pin assignments indicating an earlier age of modem to computer connectivity. The legacy of experiencing dedicated pins for transmitting, receiving and other control functions, allows serial data to be transmitted and received simultaneously i.e. entirely duplex.
Naturally, full duplex communication is a superb benefit but only when both transmitter and receiver can optimize the levels of data transmitted, and the full time intervals by which this really is done. AliBaba Dastaan E Kabul Watch Online This important function is known as 'flow control' and is implemented insurance firms one device tell another when and when never to send data, such as for example in most USB to RS485 or RS232 to RS485 converters.
In the serial communications world the precise hardware pins assigned to this function are: Data Terminal Ready (DTR) and Data Set Ready (DSR), Request To Send (RTS), and Clear To Send (CTS). By monitoring these lines the device mounted on the computer can answer an immediate upsurge in data (beyond that of its cache to handle) by lowering the 'Clear To Send' (CTS) pin signal, knowing that the computer monitoring its CTS pin will dsicover the dropped signal, and stop sending data.
It is this ability to keep a smooth data flow that is highly valued in devices that convert between, like, USB to serial RS232. Top speed USB data communicating with the much slower RS232 interface needs careful handling.
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