[FAQ]: What Multiplexers or Switches can I use for RS-232, RS-422, and RS-485 Applications?

When trying to find a multiplexer as a solution for RS-232, RS-422, and RS-485 applications. It is important to understand what parameters to look for when trying to find the right mux. Each protocol has its own requirements, but in order to make it simple. We can suggest a mux to fit all three protocols and later break it down to each protocol and its specific requirements.

A multiplexer with the following ratings can be reliably implemented in RS-232, RS-422, and RS-485 applications:

• Capable of passing a voltage signal at the range of ±7V to ±15V
• Have a rated bandwidth of at least 10MHz
• Recommended Ron to be 10Ω, or below
• Two to four signal lines configuration

Protocols Overview

RS-232

RS-232 is an asynchronous serial communication protocol. It means the information is being transmitted one bit at a time without a clock signal for synchronization. Each message instead contains start and stop bits, separated by individual frames. Those frames are indivisible packets of bits. It is a two-wire protocol.
Valid RS-232 signals are at the voltage range of ±3V to ±15V with respect to common ground. The frequency limitation is dependent on the bit rate being used on the bus.

RS-422

RS-422 is a serial, differential communication protocol. It uses a twisted pair of differential signals for receiving and transmitting data. It runs in full-duplex, with 2 wires for transmitting and 2 wires for receiving. Making it a four-wire protocol.
Valid RS-422 signals can range from 0 to 5V with respect to common ground. The signal clock rate ranges from 8KHz to 2MHz.

RS-485

RS-485 is a serial communication protocol, which uses controller and peripheral architecture, and differential signaling to send data over two twisted wires. Majority of RS-485 applications use two signal lines, implementing half-duplex communication. It can also operate at full-duplex if needed.
RS-485 is a two/four-wire protocol.
Valid RS-485 signals can range from -7V to 12V with respect to common ground. The maximum signal frequency can go up to 5MHz.

Summary

The RS-232, RS-422, and RS-485 have different levels of parametric care abouts. Each one has a different valid signal voltage range and frequency. The table below helps to break down and recommend which of our devices can be implemented in each protocol.

Recommended Devices