There are two types of RS485, one is half duplex mode with only DATA+and DATA - wires, and the other is full duplex mode with four wires for signal transmission: T＋，T－，R＋，R-。 When in full duplex mode, it can be considered as RS422.

1. The British symbols are TDA (-), TDB (+), RDA (-), RDB (+), GND

2. The American logo is Y Z 、 A 、 B 、 GND

3.中式标识为 TXD(+)/A 、TXD(-)/B 、RXD(-) 、RXD(+)、GND

Function is the ultimate effect achieved by an object as a means or tool in a certain time (or absence), space (or absence), and process.

RS485 full duplex

RS485 has two types of wiring: two-wire and four wire. The four wire system can only achieve point-to-point communication and is rarely used nowadays. The two-wire wiring method is more commonly used, which is a bus topology structure that can connect up to 32 nodes on the same bus. In RS485 communication networks, the master-slave communication method is generally used, which means that one master has multiple slaves. RS422， Introduced after RS232, TTL differential level is used to represent logic, which is represented by the voltage difference between two wires. RS422 is defined as full duplex, so at least 4 communication lines are required (usually an additional ground wire). One driver can drive up to 10 receivers (i.e. the receiver is 1/10 of the unit load). The communication distance is related to the communication speed. Generally, high-speed communication can be used for short distances, and long-distance communication can be carried out at low speeds, usually up to hundreds or even kilometers.

Which are RS232, RS422, and RS485 full duplex and which are half duplex? Is it true that the higher the number, the more advanced the version?

RS232 and RS422 are full duplex, while RS485 is half duplex. The higher the number, the more advanced the version. For example, RS485 is just a castrated version of RS422 (with 2 fewer wires). It's just a difference in the definition of the physical layer (i.e. hardware).

What is the difference between full duplex and half duplex?

1. Different properties: Full duplex transmission refers to switches being able to receive data while sending it, and the two are synchronized. Currently, switches support full duplex. There is only one action that occurs during a certain period of time. For example, on a narrow road in a day, only one car can pass through at the same time. When there are currently two cars driving in opposite directions, in this situation, only one car can pass first and wait until the end before the other car drives.

2. Different speeds: In full duplex mode, the maximum speed that a network cable can reach is over 100 Mbps, while in half duplex mode, the maximum speed that a network cable can reach is usually around 10 Mbps.

3. Different modes: Ethernet cables in full duplex mode can operate in both full duplex and half duplex modes; But half duplex network cables cannot operate in full duplex mode.

What does RS485 mean

RS-485又名TIA-485-A, ANSI/TIA/EIA-485或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 Electronics Industry Alliance. The digital communication network using this standard can effectively transmit signals over long distances and in environments with high electronic noise. RS-485 enables the configuration of low-cost local networks and multi branch communication links. [s1]

RS485 has two types of wiring: two-wire and four wire. The four wire system can only achieve point-to-point communication and is rarely used. Currently, the two-wire wiring method is more commonly used, which is a bus topology structure that can connect up to 32 nodes on the same bus.

In RS485 communication networks, the master-slave communication method is generally used, which means that one master has multiple slaves. In many cases, when connecting RS-485 communication links, it is simply necessary to use a pair of twisted pair cables to connect the "A" and "B" terminals of each interface, while ignoring the connection of the signal ground. This connection method can work normally in many situations, but it has buried great hidden dangers. The reason is common mode interference: RS-485 interfaces use differential transmission of signals, and do not need to detect signals relative to a reference point. The system only needs to detect the potential difference between the two wires, but it is easy to overlook that the transceiver has a certain common mode voltage range. The common mode voltage range of RS-485 transceivers is -7 to+12V. Only when the above conditions are met, can the entire network work normally; 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 EMI problem: the common mode part of the output signal from the driver requires a return path. If there is no low impedance return channel (signal ground), it will return to the source end in the form of radiation, and the entire bus will radiate electromagnetic waves outward like a huge antenna. Industrial control has moved from single machine control to centralized monitoring and distributed control. Nowadays, it has entered the era of the internet, and the networking of industrial controllers has also provided convenience for network management. Modbus is one of the network protocols for industrial controllers.

1. Protocol Overview

Physical layer: Transmission method: RS485

Mailing address: 0-247

Communication baud rate: adjustable

Communication medium: shielded twisted pair cable

Transmission mode: master-slave half duplex mode

The protocol uses a responsive connection (half duplex) on a single communication line, which means that signals are transmitted in opposite directions on a separate communication line. Firstly, the signal from the host computer is addressed to a unique terminal device (slave), and then the response signal sent by the terminal device in the opposite direction is transmitted to the host.

The protocol only allows data exchange between the host computer and terminal devices, and does not allow data exchange between independent devices, which does not occupy the communication line during their initialization, but is limited to responding to query signals arriving locally.

RS485 communication method

Half duplex data transmission allows data to be transmitted in two directions, but at a certain moment, data is only allowed to be transmitted in one direction. It is actually a direction switching simplex communication; At the same time, only one party can receive or send information, which can achieve two-way communication. Example: walkie talkie.

Full duplex data communication allows data to be transmitted in two directions simultaneously. Therefore, full duplex communication is a combination of two simplex communication methods, which require both the sending and receiving devices to have independent receiving and sending capabilities. They can simultaneously receive and send information at the same time, achieving bidirectional communication. Example: Telephone communication.

standard

The RS-485 standard is a half duplex communication protocol, which is suitable for both transmitting and receiving parties to share a pair of lines for communication, as well as for multiple points to share a pair of lines for bus networking.

RS-485 interface chips have been widely used in many fields such as industrial control, instruments, meters, multimedia networks, mechatronics products, etc. The types of chips that can be used for RS-485 interfaces are also increasing. How to find the most suitable chip among the various types of interface chips is a problem facing every user.

The RS-485 interface has different requirements and usage methods for chips in different usage scenarios. What factors should users consider when selecting chips and designing circuits? Due to the inherent characteristics of certain chips, some communication faults may even require corresponding adjustments in software. The RS-485 interface can be connected into two communication modes: half duplex and full duplex.

Is RS485 full duplex equivalent to RS422?

RS485 has two types of wiring: two-wire and four wire. The four wire system can only achieve point-to-point communication and is rarely used nowadays. The two-wire wiring method is more commonly used, which is a bus topology structure that can connect up to 32 nodes on the same bus. In RS485 communication networks, the master-slave communication method is generally used, which means that one master has multiple slaves.

RS422， Introduced after RS232, TTL differential level is used to represent logic, which is represented by the voltage difference between two wires. RS422 is defined as full duplex, so at least 4 communication lines are required (usually an additional ground wire). One driver can drive up to 10 receivers (i.e. the receiver is 1/10 of the unit load). The communication distance is related to the communication speed. Generally, high-speed communication can be used for short distances, and long-distance communication can be carried out at low speeds, usually up to hundreds or even kilometers.

RS485 full duplex

RS485 has two types of wiring: two-wire and four wire. The four wire system can only achieve point-to-point communication and is rarely used nowadays. The two-wire wiring method is more commonly used, which is a bus topology structure that can connect up to 32 nodes on the same bus. In RS485 communication networks, the master-slave communication method is generally used, which means that one master has multiple slaves. RS422， Introduced after RS232, TTL differential level is used to represent logic, which is represented by the voltage difference between two wires. RS422 is defined as full duplex, so at least 4 communication lines are required (usually an additional ground wire). One driver can drive up to 10 receivers (i.e. the receiver is 1/10 of the unit load). The communication distance is related to the communication speed. Generally, high-speed communication can be used for short distances, and long-distance communication can be carried out at low speeds, usually up to hundreds or even kilometers.