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RS232/RS422/RS485 -What are the differences?

This serial interface is the most common serial interface. It uses a 2 wire system to communicate. Most serial devices are compatible with this interface, and most older computers come with this port. However, this interface does have its weaknesses:

-It can only send a signal up to 50ft without any active serial extensions.
-It is limited in its data transfer speed(20kb/s).
-Since its transmit and receive lines are linked through the same ground(single-ended referenced) it tends to pick up noise.
-Only one device can connect to the port at a time(there are some rare exceptions).

RS422 does have its advantages to RS232, it also has its disadvantages. RS422 is not supported by as many devices as RS232. It also has a lot of advantages over RS232. Its main difference is that it uses 4 wires to communicate rather than 2. Some of it’s specs are as follows:

-Can support up to 32 devices on one port, through multiple switches
-Can transfer data at a higher speed than RS232(10Mb/s-100Kb/s).
-Can extend longer distances than RS232(from 500 to 4000 ft).
-It has a differential reference for its transmit and receive lines(less noise).

RS-485 has even more commonalitites with RS422 than RS232. They both support up to 32 devices, and they both have the same data transfer rate(10Mb/s-100Kb/s) and can be extended to the same length(from 500 to 4000 ft). RS485 does use less cables than RS422 since it is a 2 wire system, reducing clutter. However, RS485 is more difficult to program than RS422.


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