What does rs485 mean?

rs485, also known as TIA-485-A, ANSI/TIA/EIA-485 or TIA/EIA-485, is a standard that defines the electrical characteristics of drivers and receivers in balanced digital multipoint systems. The standard is defined by the Telecommunications Industry Association and the Electronic Industries Alliance; digital communication networks using the standard can effectively transmit signals over long distances and in environments with high electronic noise.

#The operating environment of this tutorial: Windows 10 system, Dell G3 computer.

What does rs485 mean?

RS-485 is also known as TIA-485-A, ANSI/TIA/EIA-485 or TIA/EIA-485.

RS485 is a standard that defines the electrical characteristics of drivers and receivers in balanced digital multipoint systems, defined by the Telecommunications Industry Association and the Electronic Industries Alliance. Digital communication networks using this standard can effectively transmit signals over long distances and in environments with high electronic noise. RS-485 enables connection to local networks as well as the configuration of multi-drop communications links.

RS485 has two types of wiring: two-wire and four-wire. The four-wire system can only achieve point-to-point communication. It is rarely used now. The two-wire wiring method is mostly used. This wiring method is Bus topology, up to 32 nodes can be connected to the same bus.

In the RS485 communication network, the master-slave communication method is generally used, that is, one host has multiple slaves. In many cases, when connecting an RS-485 communication link, one simply uses a pair of twisted pairs to connect the "A" and "B" ends of each interface, while ignoring the signal ground connection. This connection method is used in many The situation can work normally, but it has buried a lot of hidden dangers. Reason 1 is common mode interference: the RS-485 interface uses a differential signal transmission method, and does not need to detect the signal relative to a certain reference point. The system only It is enough to detect the potential difference between the two lines, but it is easy to overlook that the transceiver has a certain common mode voltage range. The common mode voltage range of the RS-485 transceiver is -7 to 12V. Only when the above conditions are met, the entire network can Normal operation; when the common-mode voltage in the network line exceeds this range, it will affect the stability and reliability of communication, and even damage the interface; the second reason is the problem of EMI: the common-mode part in the output signal of the sending driver needs a return path, if there is not a low The resistor's return channel (signal ground) will return to the source in the form of radiation, and the entire bus will radiate electromagnetic waves outward like a huge antenna.

The RS485 bus is a standard that defines the electrical characteristics of drivers and receivers in balanced digital multipoint systems, defined by the Telecommunications Industry Association and the Electronic Industries Alliance. rs-485 uses half-duplex working mode and supports multi-point data communication. The rs-485 bus network topology generally adopts a terminal-matched bus structure. That is, a bus is used to connect various nodes in series, and ring or star networks are not supported.

rs-485 uses balanced transmission and differential reception, so it has the ability to suppress common mode interference. In addition, the bus transceiver has high sensitivity and can detect voltages as low as 200mv, so the transmitted signal can be recovered thousands of meters away. Some rs-485 transceivers modify the input impedance to allow up to 8 times more nodes to be connected to the same bus. The most common application of rs-485 is communication between programmable logic controllers in industrial environments.

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