RS485 vs RS422 Similarities and Differences

In data communication, there are low-frequency and high-frequency communication. For low-frequency data communication, 2 wire protocols are commonly used: RS422 and RS485. Wire protocols are guidelines for the transmission of data from point to point.

Both of these "RS" protocols, RS422 and RS485, are also known as TIA-422-B, and TIA-485-A respectively.

Cables following these protocols are robust and can transmit data to long distances and in noisy environment. However, as the distance increases, the speed of data transmission decreases. The distance can be calculated using the Baud Rate chart and the frequency of data transmission can be adjusted accordingly. 

BRCReference from TIA/EIA 422

These low-frequency cables are generally used in sensors and devices that do not require high data speed.

How are these protocols, RS422 and RS485, similar or different?

Similarities

Protocols RS422 and RS485 are similar in many ways. Some of their similarities are:

  1. Both use differential signaling over twisted pairs
  2. Both can be made into full-duplex using 4 wires
  3. Both can transmit data up to 1.2km, at a rate of up to 10Mbps

Differences

Though similar, the 2 protocols are not the same. RS485 is more advanced than RS422. RS485 is backward compatible while RS422 is not. In other words, systems following RS485 are RS422 compatible but systems following RS422 are not RS485 compatible.

RS485 is convenient for multi-point interconnection and can be networked to form a distribution system that allows up to 32 drivers and 256 receivers. RS422, on the other hand, allows 1 driver and 10 receivers.

Keystone Cable's Signal Cables

At Keystone, we supply cables such as UL2464 Single Pair Signal cables, UL2464 Multi Pair - OS Signal cables, and RS485 Multi Pair Double Overall Screened cables (sample construction below). These cables can be used for both RS422 and RS485. 

 

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