Over the years, many customers have asked us to provide more information about the differences between the three main serial interfaces commonly in use today, RS-232, RS-422 and RS-485. This article will be addressing this question in specific.
RS-232 serial interface
RS232 was first introduced in 1962, This is the most common type of serial interface, it was the standard communication before the PS2 and USB become popular in the computer industry, you connect a mouse, modem, and printer to RS-232 serial interface. RS232 only allows for one transmitter and one receiver on each line. RS232 also use a Full-Duplex transmission method. RS232 can transmit up to 1Mbps with maximum distance up to 50 ft.
RS-422 serial interface
RS422 is an improved version of RS232, it uses twisted pair cable to reduce the noise, and it uses signaling balancing to transmit data, so what is signal balanced – It uses a voltage-difference between the two lines as an indication of the signal value, with this method the data is able to transmit for longer distance with faster data rates, with RS422 the data can transmit up to 10 Mpbs at 50 feet or 100 Kbps at 4000 feet. RS422 is capable of multi-drop capability, it limits up to 10 slaves in the data line.
RS485 serial interface
RS485 is an improved version of RS422, it expands on the capabilities, the major change is to have multi-drop Limitation of RS422, it allows up to 32 devices to communicate through the same data line. Any of the slave devices on an RS-485 bus can communicate with all the slave within the data line without going through the master device.
Quick Comparison Chart
For your easy reference, we have prepared a quick comparison chart to demonstrate the key differences of these 3 commonly used serial interfaces for industrial applications. Hope you will find this chart useful and please let us know if you have any additional question.
|Cabling||Single ended||Single ended multi-drop||Multi-drop|
|No. of Devices||1 transmitter|
|Communication Mode||Full duplex||Full duplex,|
|Max Distance||50 feet at 19.2 kbps||4000 feet at 100 kbps||4000 feet at 100 kbps|
|Max Data Rate||1 mbps for 50 feet||10 mbps for 50 feet||10 mbps for 50 feet|