Despite the widespread utilization of Universal Serial Bus (USB) ports, for many of our customers who use converters, serial ports continue to be an essential interface. Not just on computers, but in addition cameras, printing equipment, modems and a wide variety of industrial automation network equipment, continue steadily to utilize serial port connectivity. (Although, if you examine computers manufactured within the past few years, you'll probably find only one serial port along with, on some models, a parallel port.)
Among the great benefits of serial communications is the simplicity attained by taking 8-bit bytes and transmitting them one bit at any given time down a single wire. This keeps 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.
How do serial communications actually work? Well, although we mentioned the serial transfer of 8 bits on the wire, actually 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 referred to as a 'Universal Asynchronous Receiver/Transmitter' (UART). This chip is a screen between the interior computer bus's parallel communications, and the serial ('Com') port. Some UART chips are able to cache significant amounts 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 being used today contain 9 or 25 pins, with the pin assignments indicating an early on age of modem to computer connectivity. The legacy of having dedicated pins for transmitting, receiving and other control functions, allows serial data to be transmitted and received simultaneously i.e. in full duplex.
Naturally, full duplex communication is a great benefit but only if both transmitter and receiver can optimize the amounts of data transmitted, and enough time intervals in which that is done. AliBaba Dastaan E Kabul Watch Online This important function is recognized as 'flow control' and is implemented by having one device tell one other when and when never to send data, such as for instance in most USB to RS485 or RS232 to RS485 converters.
In the serial communications world the particular hardware pins assigned to the 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, understanding that the computer monitoring its CTS pin might find the dropped signal, and stop sending data.
It's this ability to keep a clean data flow that is highly valued in devices that convert between, for example, USB to serial RS232. High speed USB data communicating with the much slower RS232 interface needs careful handling.
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