485 bus system and asynchronous half-duplex communication method thereof

Abstract

The invention relates to the field of transmission control and discloses a 485 bus system and an asynchronous half-duplex communication method thereof. 485-bus half-duplex communication is realized by fewest cables, all devices with mutual data transmission are connected equivalently without principal and subordinate relation, and any device can send data to any other device. The 485 bus system comprises a plurality of devices connected by 485 buses, wherein each device is provided with three signal interfaces, two signal interfaces are a pair of 485-bus data transmission differential signal interfaces, the other signal interface is a collision detection signal interface, and the same signal interfaces of all the devices are mutually connected by wires; the asynchronous half-duplex communication method comprises the following steps of: when the devices need to send data, detecting the state of collision detection signals; if detecting to be in a busy state, waiting till to be in an idle state; if detecting to be in the idle state, sending data after setting the collision detection signals in the self collision detection signal interfaces of the devices to be in a busy state.

Description

technical field [0001] The invention relates to the field of transmission control, in particular to a 485 bus communication technology. Background technique [0002] In the RS485 communication network, the master-slave communication mode is generally adopted, that is, one master device with multiple slave devices, or one master device with multiple slave devices, each action is initiated by the master device, and the slave devices are executed after distinguishing by address corresponding action. [0003] The RS485 communication mode is usually an asynchronous half-duplex mode. The so-called half-duplex mode means that information can be sent in two directions between two devices, but cannot be sent at the same time. The so-called asynchronous communication means that the asynchronous parties do not need a common clock, that is, the receiver does not know when the sending device will send, and there is information in the sent data that prompts the receiver to start receivin...

AI Technical Summary

Problems solved by technology

[0006] The inventors of the present invention have found that the existing RS485 bus system asynchronous half-duplex communication technology can only adopt the mode of the master asking the slave to answer, and the communication efficiency is low

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