Differences between RS232 , RS422 and RS485

what are the differences between RS 232 , RS485 , RS232

For understanding the difference between RS2332 , RS485 and Rs 232 it is essential to understand Single ended Transmission or Balanced Differential Transmission or Unbalanced

Single ended transmission

Single ended transmission is performed on One signal line and its output and throughput with respect to ground.One common ground is sufficient if the interface is simple and low speed.For more advanced interfaces single return path for each signal in line twisted pair cable is required Advantages of single ended transmission are Low system cost Simple to Implement

Disadvantages of Single ended transmission Noise and crosstalk Ground shifts Low data rates Low line length

Differential tranmission

For differential transmission a pair conductor is necessary for each channel.One line transmit the true signal while the second line transmit the inverted or false signal transmitted. Ground return line is required to have an interconnection on driver and receiver.

Advantages Low sensitivity to crosstalk Ground Noise rejection Common mode noise rejection High signalling rates Long length upto 1200m

Disadvantages Twisted pair cable is required Higher cost

Different Bus topolgy Point to Point - consist of one driver and one reciever Multi Drop - One driver with Multiple reciever Multi Point - Multiple drivers and Multiple Recievers

Different bus topology Single Drop and Multi drop

RS 232 Transmission is Single Ended Point to Point Bus toplogy At Driver End Logic 0 - 5v to 15v Logic 1 - 5v to -15v

At Reciever End Logic 0 +3 to 15v Logic 1 -3 to -15v

Voltages between -3 to 3 is undefined and it is transition region

RS 422 Transmission is

Differential Multi drop interface. It allows to connect upto 10 receivers to a driver

RS 485 is

Differential Multi Point interface Up to 32 devices can be connected

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