RS485 distributed bus system based control method

A bus system and control method technology, applied in the direction of instruments, electrical digital data processing, etc., can solve the problems of small number of stations, poor real-time performance, and inability to develop, and achieve the effects of avoiding conflicts, low requirements, and simple implementation methods

Inactive Publication Date: 2016-02-24
上海海视电子有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this technology has shortcomings such as low utilization rate of RS485 bus resources, poor real-time performance, and a small number of stations, so it cannot be developed into "RS485 field bus".

Method used

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  • RS485 distributed bus system based control method
  • RS485 distributed bus system based control method
  • RS485 distributed bus system based control method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0086] Take 9600 baud rate, 1 as the start bit, 8 bits of data, 1 bit of checksum, 1 bit of stop bit, a total of 11 bits of asynchronous serial communication as an example; if the CPU type of the node device is involved, the frequency of the crystal oscillator is 11.0592 M's 51 series MCU (such as 8952) as an example; involving RS485 communication chip, take TexasInstrumentsSN75176 as an example.

[0087] 1. Calculate the time required to send 1 bit

[0088] The time required to send 1 bit=1 / communication baud rate=1 / 9600=104(us)

[0089] 2. Bus detection cycle

[0090] Taking the detection bus cycle as the gap time to detect the bus state, the present invention does not directly detect the differential signal of the RS485 bus by adding hardware devices, but permanently enables the receiving end (RE) of the RS485 communication chip of the system control device to detect and receive If the level of the receiving end (R) is 0, the bus state is called busy; otherwise, the recei...

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Abstract

The invention discloses an RS485 distributed bus system based control method. Each node in an RS485 distributed bus is only in a receiving state at the beginning, and a state of the RS485 distributed bus is monitored; when the node needs to transmit an instruction or data, a bus control right competition obtaining mechanism is started; the state of the RS485 distributed bus is closely detected; if the state of the bus is always in an idle state within a certain time (bus competition delay detection time), it is determined that the RS485 distributed bus is in the idle state, a transmission enable pin ''TE'' of an RS485 chip of the node can be set, the bus is occupied, and the data are transmitted in time; and until the data of the node is completely transmitted, the transmission enable pin ''TE'' of the RS485 chip of the node is eliminated and resources of the RS485 distributed bus are released. The control method adopts the technical scheme that a bus control right is obtained through competition by monitoring the idle state of the bus.

Description

technical field [0001] The invention relates to a control method based on an RS485 distributed bus system. The invention is suitable for asynchronous serial communication, especially for data communication where the data communication is not very frequent, the communication baud rate is not more than 19200BPS, the short frame communication structure is adopted, and the effective byte number of each frame is 1-255 variable data communication , automatic control and other application systems. Background technique [0002] The RS-485 interface has the advantages of good anti-noise interference, long transmission distance and multi-site, making it the preferred asynchronous serial communication interface. It is widely used in the field of security, especially in TV monitoring systems. [0003] The RS-485 network topology generally adopts a terminal-matched bus-type structure (straight-line topology), and does not support ring or star networks. RS-485 is very convenient for mul...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F13/364
CPCG06F13/364G06F2213/0002
Inventor 周海令
Owner 上海海视电子有限公司
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