Techniques for Serial Data Calls

Despite having the widespread usage of Universal Serial Bus (USB) ports, for many of our customers who use converters, serial ports remain an important interface. Not only on computers, but also digital camera models, printing equipment, modems and a wide variety of industrial automation network equipment, continue to make use of serial port connectivity. (Although, in the event that you examine computers manufactured within the past couple of years, you'll probably find just one single serial port alongside, on some models, a simultaneous port.)

Among the great advantages of serial communications is the simplicity attained by taking 8-bit bytes and transmitting them one bit at a 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, 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 reality control bits may also be transmitted. A 'start' bit to indicate data is arriving, a 'stop' bit to indicate 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 an interface between the inner 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 used today contain 9 or 25 pins, with the pin assignments indicating an earlier age of modem to computer connectivity. The legacy of getting 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 good benefit but only if both transmitter and receiver can optimize the amounts of data transmitted, and enough time intervals in which this is done. AliBaba Dastaan E Kabul Watch Online This important function is recognized as 'flow control' and is implemented with one device tell another when and when never to send data, such as for example 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 with 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, realizing that the computer monitoring its CTS pin might find 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.