What is RS-232?
RS-232 is an internet protocol that stands for Recommended Standard 232. It was introduced in the 1960s for data transferring. This protocol is used for medium distances. It works by connecting a computer terminal to a circuit-terminating terminal. This widely used internet protocol operates on full duplex mode (simultaneous two-way directional communication).
The maximum operational distance for RS-232 is approximately 15 meters, and it operates on a level-based system of voltage which works efficiently with a minimal difference of ground potential. However, in areas with noisy electrical environments, data corruption might occur. With point-to-point line configuration, its maximum data transmission rate is 1 M Bits/s.
What is RS-485?
RS-485 is an internet protocol first introduced in 1998 by a joint alliance of the Telecommunications Industry Association and the Electronic Industries Alliance. Unlike RS-232, it works on two lines, A and B. RS-485 can be connected with approximately 32 devices, but only a single device can ‘talk’ at a specific time. Although it works in half-duplex mode, it has faster transfer speeds than RS-232.
Its maximum operational distance is 15 meters and it operates on a different voltage system. Its transmission rate is about 10 M Bits/s. The newer versions of RS-485 now also use a USB interface. It is also immune to high levels of noise immunity. It consumes low voltage to transfer data over long distances. However, the use of termination resistors reduces their usage.
What is RS-422?
RS-422 is an internet protocol developed by the Electronic Industries Alliance in 1975. It serves the purpose of transmission of data for longer distances. Although it is similar to RS-232 and RS-485, it has unique properties. It operates on the full-duplex mode like RS-232 but uses a different voltage system similar to RS-485. The data transfer speed is also better than RS-232, similar to the 10 M Bits/s of RS-485.
RS-422 is not typical because the data transfer rate reduces with the maximum increase in the length of cables. As RS-422 is not multi-point, this makes it unidirectional, meaning that only a single driver and a receiver are connected. In contrast to RS-485, RS-422 only permits multiple receivers instead of multiple drivers.
Difference Between RS-232 and RS-485, and RS-422
- RS-232 was launched in the 1960s; RS-485 was available in 1998; RS-422 was introduced in 1975.
- Electronic Industries Association is the manufacturer of the RS-232; RS-485 by joint efforts of the Telecommunications Industry Association and the Electronic Industries Alliance; the Electronic Industries Alliance manufactured RS-422.
- RS-232 is voltage level based; RS-485 operates on a differential system of voltage RS-422 has differential voltage signaling.
- RS-232 uses full-duplex mode; RS-485 works on half-duplex mode; full-duplex mode is present in RS-422.
- RS-232 utilizes point-to-point line configuration; RS-485 uses multi-drop line configuration; RS-422 operates on either point-to-point or multi-drop line configuration.
Comparison Between RS-232 and RS-485, and RS-422
| Parameters of Comparison | RS-232 | RS-485 | RS-422 |
| Duplex Mode | Full-duplex | Half-duplex | Full-duplex |
| Voltage System | Level-based | Differential | Differential |
| Operational Distance | 15 meters | 1200 meters | 1200 meters |
| Data Transmission Rate | 1 M bits/s | 10 M Bits/s | 10 M Bits/s |
| Line Configuration | Point-to-point | Multi-drop | Point-to-point or multi-drop |