Even with the widespread usage of Universal Serial Bus (USB) ports, for quite a few customers who use converters, serial ports remain an essential interface. Not only on computers, but in addition digital cameras, printing equipment, modems and a wide range of industrial automation network equipment, continue to make use of serial port connectivity. (Although, in the event that you examine computers manufactured in the last couple of years, you'll probably find only one serial port along with, on some models, a parallel port.)
Among the great benefits of serial communications could be the simplicity achieved by taking 8-bit bytes and transmitting them one bit at any given time down just one 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, rather than in parallel, is eight times slower! (Remember that parallel ports were developed after serial ports.
How can 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 finished, and an (optional) parity bit.
The 'electronic brains' behind this data transmission is a dedicated silicon chip known as a 'Universal Asynchronous Receiver/Transmitter' (UART). This chip is a software between the interior computer bus's parallel communications, and the serial ('Com') port. Some UART chips can cache significant amounts of data from the computer bus while simultaneously transmitting onto standard serial ports at rates all the way to 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. completely duplex.
Naturally, full duplex communication is a great benefit but only when both transmitter and receiver can optimize the amounts of data transmitted, and the time intervals where this really is done. AliBaba Dastaan E Kabul Watch Online This important function is called 'flow control' and is implemented by having one device tell the other when and when not to send data, such as in many USB to RS485 or RS232 to RS485 converters.
In the serial communications world the specific 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 attached to the computer can respond to a sudden 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 will dsicover the dropped signal, and stop sending data.
It is this ability to keep a smooth data flow that's highly valued in devices that convert between, for instance, USB to serial RS232. Top speed USB data communicating with the much slower RS232 interface needs careful handling.
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