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An introduction to serial RS232

The RS232 serial interface is an interface for communicating data by way of transmission. It was introduced in 1969 by a committee that now goes by the name of Electronics Industry Association. Together with Telecommunication Industry Association, they have managed to maintain the product in the market, despite the notion that is commonly held by many: Serial RS232 / RS485 ports are archaic and should have met their 'demise' by now. However, serial ports, especially RS232 which is probably the most enduring of all serial ports, are very common today. RS485 and RS422 are more commonly used in industrial environments.

The two bodies, Electronics Industry Association and Telecommunication Industry Association, have set up standards for serial data transfer. It is due to this administration that the port is now commonly referred to as EIA/TIA -232. The reason behind the name is to reflect the initials of the organizations that run it. Right now, these organizations have made other serial ports in the same series of RS serial ports. The latest model is RS 232C which is a 'superset' of RS232. This means that it has all the capabilities that RS232 model has but, in addition, it has more qualities that RS232 doesn't have; it also has 25 pins while RS232 usually use 9 pins. Other models are RS422 and RS485.

When dealing with data, there are two types of communication that exist: differential and single-ended. RS232 deals with single-ended data communication and it defines a communication between two gadgets or equipments: DTE (Data Terminal Equipment) and DCE (Data Circuit-Termination Equipment). The difference between the two equipments lies in their pin out assignments. An example of a DTE is a PC while that of a DCE is a dial up modem. The two are connected using a RS 232 link cable known as a straight-through -  which transfers pin maps to transfer pins and to receive pin maps, it receives pins - ,  or uses a null modem (a type of a crossover) to connect between two DTE equipments like personal computers.

The RS232 serial port uses independent cannels that are fully duplex, whereas RS485 is half duplex. This means that the RS232 device can send and receive data at the same time. This usually involves three wires; one of the wires sends RS232 data, the other wire receives RS232 data and the other one is the earth-grounding wire which expedites transmission of RS232 data. By using 9 pins, this type of RS232 and RS232 to RS485 communication is possible.

Even with all those capabilities, there are some limitations, however. RS232 and RS485 ports transmits data in single bit format using asynchronous mode of transmission. This makes communication very slow, and hence many people prefer using other computer interface peripherals like USB. The latter, USB, is faster than RS232 serial port and has supplanted it in many machines. One of the reasons why RS232 and RS485 serial ports are still in use today is sometimes because the cost of replacing them, in expensive machines like those in the factories, but also because RS232 and RS485 actually is compatible with many devices and can easily be integrated with existing software solutions.

For further information regarding serial data communication please visit http://www.USconverters.com.


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