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.

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

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