The advantages and characteristics of RS485

In data communication, computer network and Industrial Distributed Control System, serial communication is often used to achieve the purpose of remote information exchange. At present, a variety of interface standards can be used for serial communication, the most commonly used interfaces are RS-232, RS-422, RS-485.

1. ELECTRICAL CHARACTERISTICS OF RS-485: DIFFERENTIAL SIGNAL NEGATIVE LOGIC, logic "1" is expressed as + (2 ~ 6) v between two lines, and logic "0" is expressed as-(2 ~ 6) v between two lines. The interface signal level is lower than RS-232-C, so the chip of the interface circuit is not easily damaged, and the level is compatible with the TTL level, making it easy to connect with the TTL circuit.

2. The maximum data transmission rate of RS-485 is 10 Mbps.

3. Rs-485 interface is a combination of a balanced driver and a differential receiver, which can enhance the ability of anti-common-mode interference.

4. The maximum communication distance of RS-485 is about 1219m, and the maximum transmission rate is 10Mbps. The transmission rate is inversely proportional to the transmission distance. At the transmission rate of 100KbpS, the maximum communication distance can be reached. The RS-485 bus generally supports a maximum of 32 nodes, if using a special 485 chip, can reach 128 or 256 nodes, the maximum can support to 400 nodes.

RS232 is the earliest serial interface standard, which is widely used in short distance and low baud rate serial communication. The later developed RS-422 and RS-485 are the electrical standards of balanced transmission. Compared with RS-232 non-balanced transmission, RS-422 and RS-485 are greatly improved in the electrical index.