CN102053935A - MODBUS serial communication protocol-based communication method - Google Patents

MODBUS serial communication protocol-based communication method Download PDF

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Publication number
CN102053935A
CN102053935A CN2010105713384A CN201010571338A CN102053935A CN 102053935 A CN102053935 A CN 102053935A CN 2010105713384 A CN2010105713384 A CN 2010105713384A CN 201010571338 A CN201010571338 A CN 201010571338A CN 102053935 A CN102053935 A CN 102053935A
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China
Prior art keywords
data
slave station
main website
sends
ready
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CN2010105713384A
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Chinese (zh)
Inventor
龙斌
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Guangdong Yada Electric Co Ltd
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Guangdong Yada Electric Co Ltd
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Publication date
Application filed by Guangdong Yada Electric Co Ltd filed Critical Guangdong Yada Electric Co Ltd
Priority to CN2010105713384A priority Critical patent/CN102053935A/en
Publication of CN102053935A publication Critical patent/CN102053935A/en
Pending legal-status Critical Current

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Abstract

The invention relates to the related technical field of serial communication protocols, in particular to a MODBUS serial communication protocol-based communication method. The method comprises the following steps that: a master station sends detection character data to a slave station; the master station searches whether the slave station is ready or not according to a slave station address stored in the master station; the master station sends configuration data to the slave station; the master station sends and receives input/output data; and the slave station enters a ready state after being initialized, determines a Baud rate according to the detection character data, returns ready information to the master station, and enters an exchange state to exchange data with the master station when the configuration data is detected and is consistent with the input/output data stored in the slave station. In the invention, 1, functions are enriched on the basis of MODBUS, and the functions of bus state query, the configuration data and the like are added; 2, a standard master station program is provided and can be convenient and practical as long as a user modifies a provided header file; and 3, the slave station can automatically adapt to a plurality of Baud rates, and provides the bus state and multiple kinds of diagnostic information.

Description

A kind of means of communication based on the MODBUS serial communication protocol
Technical field
The present invention relates to the correlative technology field of serial communication protocol, particularly a kind of means of communication based on the MODBUS serial communication protocol.
Background technology
MODBUS is a kind of serial communication protocol, be Modicon in 1979, deliver for using programmable logic controller (PLC) (PLC).In fact, it has become the industrial circle communication protocol standard, and is connected mode quite commonly used between the industrial electrical equipment now.
The traditional analog control system adopts man-to-man equipment line, connects respectively by control loop.Between the measuring transducer and controller at scene in the pulpit, controller and between the actuator at scene, switch, motor, be man-to-man physical connection.Field bus control system can be realized a plurality of signals of transmission on a pair of electric wire, as operational parameter value, a plurality of equipment state, failure message etc.So just create conditions for simplied system structure, economize on hardware equipment, saving stube cable and various installation, maintenance cost.
Multiple popular fieldbus is arranged now, and they are mature and reliable very, but these buses are no matter be main website equipment or all very expensive from station equipment.For middle-size and small-size automation control system, field apparatus has only below 400, and the data volume of communication is very not big, is using current popular fieldbus too expensive under the condition like this.And using serial communication based on the MODBUS agreement, cost is very low, and the MODBUS agreement is used very extensive.Unfortunately the MODBUS agreement did not all further develop in a lot of years, each producer is according to MODBUS agreement do-it-yourself main website or slave station program, compatible very poor like this, reliability also has no idea to guarantee, the speed of communication is generally 9600bps, the corresponding time of slave station is also very slow, so the robotization control that is far from suitable is used.
Summary of the invention
The invention provides a kind of means of communication, to solve the technical matters of using MODBUS protocol compatibility difference in the prior art based on the MODBUS serial communication protocol.
In order to realize goal of the invention of the present invention, the technical scheme of employing is as follows:
A kind of means of communication based on the MODBUS serial communication protocol, the described means of communication are used for realizing serial communication that between main website and slave station described method comprises:
Following steps are carried out in the main website aspect:
At first main website sends to slave station and detects character data;
Whether ready according to the tributary address inquiry slave station that is kept at main website then;
If slave station is ready, main website sends configuration data to slave station;
Whether main website inquiry slave station enters swap status, if slave station enters swap status, then main website sends and receives inputoutput data;
Following steps are carried out in the slave station aspect:
After the slave station initialization, enter ready state, wait for then and detect character data;
When receiving the detection character data, then determine baud rate according to detecting character data, return ready information to main website, and wait for that main website sends configuration data;
When detecting configuration data, and the consistent then slave station with the inputoutput data that is kept at slave station of configuration data enters swap status, and sends to main website and to enter exchange state information and main website carries out exchanges data.
As a kind of preferred version, described method also comprises:
Main website is after slave station takes place to detect character data, whether slave station is repeatedly inquired about according to the tributary address that is kept at main website by main website ready, if surpass predefined standby condition inquiry threshold value, do not receive the ready information of slave station yet, then the judgement inquiry makes mistakes and provides warning information.
As a kind of preferred side, described method also comprises:
Main website repeatedly inquires about slave station and whether enters swap status, if surpass predefined swap status inquiry threshold value, does not receive the exchange state information that enters of slave station transmission yet, and then the main station judging inquiry makes mistakes and provides warning information.
As a kind of preferred side, described method also comprises:
Main website detects customer-furnished header file, according to the communications parameter in the header file, the detection character data that sends to slave station is set.
As a kind of preferred side, described method also comprises:
The inputoutput data that main website and slave station send, according to the transmission COS of the function code judgment data frame of the Frame of inputoutput data:
If the transmission COS is judged as the transmission data and needs acknowledgement type:
Then receiving end need send acknowledgement frame, if transmitting terminal does not receive the confirmation frame in official hour, then the judgment data frame sends and makes mistakes, and repeating data is transmitted;
If the transmission COS is judged as the transmission data and need not acknowledgement type:
Then receiving end does not send acknowledgement frame;
If the transmission COS is judged as transmission and request msg needs answer type:
Then transmitting terminal is when receiving end sends data, request receiving end answer data, receiving end need send acknowledgement frame and answer data, if transmitting terminal does not receive the confirmation frame or does not receive the answer data that receiving end sends in official hour, then the judgment data frame sends and makes mistakes, and repeating data is transmitted.
The present invention improves aspect three, and first: enrich function on the basis of MODBUS, increase the bus state inquiry, functions such as configuration data.Second: standard main website program is provided, and the user can be as long as the header file that provides be provided, and just energy is easily practical.The 3rd: slave station can adapt to a plurality of baud rates automatically, and bus state is provided, multiple diagnostic message.
Description of drawings
Fig. 1 is the process flow diagram of embodiment of the invention main website;
Fig. 2 is the process flow diagram of embodiment of the invention slave station.
Embodiment
The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.
Be the process flow diagram of the embodiment of the invention as depicted in figs. 1 and 2, comprise the steps:
Following steps are carried out in the main website aspect:
At first main website sends a string special character data to slave station;
Whether ready according to the tributary address inquiry slave station that is kept at main website then;
If slave station is ready, main website sends configuration data to slave station;
Whether main website inquiry slave station enters swap status, if slave station enters swap status.Then main website sends and receives inputoutput data;
Following steps are carried out in the slave station aspect:
After the slave station initialization, enter ready state, wait for then and detect character data;
When receiving the special character data, then determine baud rate according to the special character data, return ready information to main website, and wait for that main website sends configuration data;
When detecting configuration data, and the consistent then slave station with the inputoutput data that is kept at slave station of configuration data enters swap status, and sends to main website and to enter exchange state information and main website carries out exchanges data.
Present embodiment uses 3 times in 7 levels of OSI Reference Model, is respectively: Physical layer, data link layer, client layer.
1.1 Physical layer is a kind of medium, comprises length and topological structure, bus interface, website number and can adapt to different application at 9.6kbit/s to message transmission rate variable between the 500kbit/s.On user interface, have common access mode, host-host protocol and common service.
Physical layer type 1 (being included in the second portion of this standard) is formulated according to EIA standard RS-485:
Topology: linear bus has terminal organ at two ends, stub≤0.3m, no branch;
Medium: Shielded Twisted Pair
Total line length :≤1200 meters
Website number: 32 (main website, slave station or repeaters)
Message transmission rate: 9.6/19.2/93.75/187.5/500kbits/s.
Physical layer type 2 (formulate according to IEC 61158-2, be included in the Session 9 of this standard)
Satisfy essence
The requirement of safety (IS):
Topology: linear bus has terminal organ at two ends, stub (Spur) length overall≤120 meters;
Medium: twisted-pair feeder or multiconductor cable (shielding or non-shielding);
Total line length :≤1900 meters, relevant with type of cable;
Website number: 32 (main website, slave station or repeaters);
Message transmission rate: 31.25kbits/s.
1.2 data link layer
Medium accesses control protocol (MAC), data transport service and management service conformance with standard DIN 19241-2, GB/T9469 (PROWAY C), the definition of ISO 8802-2 and ISO/IEC JTC I/SC 6N 4960 (LLC Class1 and LLC type 3).
Eight hytes (character) form is UART form FT 1.2 (taking up-stop synchronous asynchronous transmission), as to the definition of remote control equipment and system (IEC 870-5-1).Transmission mode is the RTU pattern.The Modbus information frame uses the RTU pattern, and information sends and will begin with the pause interval of 3.5 character times at least.Under the network baud rate various character time, this is the easiest realization.First territory of transmission is the device address.Operable transmission character is hexadecimal 0...9, A..F.The continuous detection bus of network equipment comprises that pause interval is in the time.When first territory receives, each equipment all decode with judge whether to mail to oneself.In the end after transmission character, the end of message has been demarcated in the pause of one at least 3.5 character times.A new message can begin after this pauses.
Whole message frame must be failed as a continuous circulation.If the dead time that surpasses 1.5 character times was arranged before frame is finished, receiving equipment will refresh incomplete message and suppose that next byte is the address field of a new information.Similarly, if new information message before following in the time less than 3.5 characters begins, the equipment of reception will think that it is the continuity of last message.This will cause a mistake, because the value in last CRC territory can not be correct.One typical message frame is as follows:
Other particular contents please refer to the MODBUS agreement
By simplifying the Modbus function code, function code is defined as follows several data transport service:
Sending data need reply
This service allows the user to send data for single distant station.If wrong, repeating data is transmitted.
Sending data need not to reply
This service allows the user to give single distant station, a plurality of distant station (multicasting) simultaneously or sends data for simultaneously whole distant stations (broadcasting), without any need for affirmation.
Transmission and request msg need be answered
This service allows the user to send data for single distant station, asks this distant station answer data simultaneously.If wrong, repeating data is transmitted.
1.3 application layer
From communication parter (service characteristic) viewpoint, FMS describes communication object, service and relational model.
At the scene and procedure level, the purpose of communication be between two communication stations, transmit data (as, the read/write measured value is packed/start/shut down procedure processing events etc. into).
For communicating by letter between the application process of the application process of an equipment and another equipment, the process object that is transmitted must allow communication system know, in other words, the process object must be listed in (OD is similar to the public telephone book) in the object dictionary (OD) as communication object.Like this, the communication object of an application process must be visual and effective before the communication service addressing and being handled.For effective communication, the application process of communicating by letter with distinct device needs than communication object more information.
Usually, between run duration station and station, certain distance or can not be approaching is arranged, therefore, in network, must discern them uniquely with their characteristic.Can read such as relevant datas such as manufacturer's title, model, professional etiquettes by bus.In addition, all be very important aspect about the information of device communication interface status information and real equipment (as, indication at date of payment etc.).
The public object dictionary that is provided by all stations that are connected on the bus, standardized device characteristics, identical service and accordant interface constitute the basis of the equipment room open communication of different manufacturers.This compatible part of an equipment claims virtual field device (VFD).
To virtual field device, this standard is only described the effect of service to the communication object of using process.Virtual field device is not the proposition of this standard to the map of real equipment.Applied layer interface (ALI) is arranged between application layer and the actual application.
Visit the service of application layer by this intermediary interface.It provides additional communication function to adapt to the needs of application process.In addition, Applied layer interface is done the map of virtual field device to real scene equipment.
Second: standard main website program is provided
Standard main website routine library provides various programs such as standard transmitting/receiving program, diagnostic routine, configuration program, and these functions can be added by header file.Header file comprises various communications parameters, for example: baud rate, check bit, the delay time of standing, inputoutput data, diagnostic data.The client just can be easily and the slave station device talk as long as revise these parameters.
At first main website program checkout oneself state if main website is ready, then sends a string special character data, so that slave station can correctly be distinguished baud rate.Whether the address lookup slave station that provides according to the user is ready then, and whether bus is normal.Also be not ready for if detect slave station, main website sends to this slave station inquiry slave station state always, and after N time, standard main website program sends main website standard diagnostics information, and the prompting main website is wrong.If slave station is ready, main website sends configuration data to slave station, and whether main website N slave station of inquiry enters swap status, if N slave station all do not enter swap status, standard main website program sends main website standard diagnostics information.If slave station swap status.Then main website sends and receives inputoutput data.
The the 3rd: the slave station program
Now a lot of single-chip microcomputer clock frequencies are all very fast, unusual affluent resources, for example: a plurality of timers; The UART baud rate can reach more than the 1Mbps, can discern special character baud rate, hardware flow control automatically; DMA data direct access function can just can automatic reception send serial data without CPU control.Use real-time system, it is higher that communication task is put into priority ratio, and the delay time of standing is like this determined maximal value.
Reply by cable on the slave station into after, the initialization serial ports enters ready state then, waits for special character then, determines baud rate.Wait for the main website configuration data again, if the same swap status that just enters of inputoutput data of configuration data and slave station configuration.Carry out the correct data exchange with main website.The own state of slave station and real-time update is so that the main website inquiry.

Claims (5)

1. means of communication based on the MODBUS serial communication protocol, the described means of communication are used for realizing serial communication that between main website and slave station it is characterized in that, described method comprises:
Following steps are carried out in the main website aspect:
At first main website sends to slave station and detects character data;
Whether ready according to the tributary address inquiry slave station that is kept at main website then;
If slave station is ready, main website sends configuration data to slave station;
Whether main website inquiry slave station enters swap status, if slave station enters swap status, then main website sends and receives inputoutput data;
Following steps are carried out in the slave station aspect:
After the slave station initialization, enter ready state, wait for then and detect character data;
When receiving the detection character data, then determine baud rate according to detecting character data, return ready information to main website, and wait for that main website sends configuration data;
When detecting configuration data, and the consistent then slave station with the inputoutput data that is kept at slave station of configuration data enters swap status, and sends to main website and to enter exchange state information and main website carries out exchanges data.
2. the means of communication according to claim 1 is characterized in that, described method also comprises:
Main website is after slave station takes place to detect character data, whether slave station is repeatedly inquired about according to the tributary address that is kept at main website by main website ready, if surpass predefined standby condition inquiry threshold value, do not receive the ready information of slave station yet, then the judgement inquiry makes mistakes and provides warning information.
3. the means of communication according to claim 1 is characterized in that, described method also comprises:
Main website repeatedly inquires about slave station and whether enters swap status, if surpass predefined swap status inquiry threshold value, does not receive the exchange state information that enters of slave station transmission yet, and then the main station judging inquiry makes mistakes and provides warning information.
4. the means of communication according to claim 1 is characterized in that, described method also comprises:
Main website detects customer-furnished header file, according to the communications parameter in the header file, the detection character data that sends to slave station is set.
5. the means of communication according to claim 1 is characterized in that, described method also comprises:
The inputoutput data that main website and slave station send, according to the transmission COS of the function code judgment data frame of the Frame of inputoutput data:
If the transmission COS is judged as the transmission data and needs acknowledgement type:
Then receiving end need send acknowledgement frame, if transmitting terminal does not receive the confirmation frame in official hour, then the judgment data frame sends and makes mistakes, and repeating data is transmitted;
If the transmission COS is judged as the transmission data and need not acknowledgement type:
Then receiving end does not send acknowledgement frame;
If the transmission COS is judged as transmission and request msg needs answer type:
Then transmitting terminal is when receiving end sends data, request receiving end answer data, receiving end need send acknowledgement frame and answer data, if transmitting terminal does not receive the confirmation frame or does not receive the answer data that receiving end sends in official hour, then the judgment data frame sends and makes mistakes, and repeating data is transmitted.
CN2010105713384A 2010-11-25 2010-11-25 MODBUS serial communication protocol-based communication method Pending CN102053935A (en)

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CN103188122A (en) * 2013-03-19 2013-07-03 深圳市汇川控制技术有限公司 Communication system and communication method based on CAN (Controller Area Network)
CN103581228A (en) * 2012-07-26 2014-02-12 深圳市生基科技有限公司 Method and system for device communication in Internet of Things
CN104580187A (en) * 2014-12-31 2015-04-29 厦门为那通信科技有限公司 Method for achieving interaction of external devices of different MODULEBUS protocols and server
CN104717023A (en) * 2015-04-03 2015-06-17 上海航天测控通信研究所 Communication performance predictable 1553B bus engineering telemetric data acquiring method
CN106095717A (en) * 2016-06-27 2016-11-09 哈尔滨明快机电科技有限公司 A kind of dynamic retardation compensation method and device
CN106372027A (en) * 2016-08-31 2017-02-01 江苏茶花电气股份有限公司 Serial communication protocol of single chip microcomputer
CN109669372A (en) * 2018-12-24 2019-04-23 苏州谷夫道自动化科技有限公司 A kind of configuration method and device
CN110470343A (en) * 2019-08-29 2019-11-19 苏州艾铭森科技有限公司 A kind of iron-smelting furnace heat dissipation of exhaust fume monitoring system based on Modbus communications protocol
CN111245694A (en) * 2019-09-17 2020-06-05 浙江中自机电控制技术有限公司 Fault processing method based on Modbus extended communication
CN111327503A (en) * 2020-03-10 2020-06-23 浙江明度智控科技有限公司 MODBUS bus-based multi-master-station token scheduling device, communication method and system
CN111683038A (en) * 2020-04-17 2020-09-18 许继集团有限公司 Fire alarm control system data processing method and device based on modbus protocol

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103581228A (en) * 2012-07-26 2014-02-12 深圳市生基科技有限公司 Method and system for device communication in Internet of Things
CN103188122A (en) * 2013-03-19 2013-07-03 深圳市汇川控制技术有限公司 Communication system and communication method based on CAN (Controller Area Network)
CN103188122B (en) * 2013-03-19 2017-05-03 深圳市汇川控制技术有限公司 Communication system and communication method based on CAN (Controller Area Network)
CN104580187A (en) * 2014-12-31 2015-04-29 厦门为那通信科技有限公司 Method for achieving interaction of external devices of different MODULEBUS protocols and server
CN104580187B (en) * 2014-12-31 2018-09-04 厦门为那通信科技有限公司 A method of realizing that the external device of different MODULEBUS agreements is interacted with server
CN104717023B (en) * 2015-04-03 2017-11-28 上海航天电子通讯设备研究所 The predictable 1553B buses engineering telemetry acquisition methods of communication performance
CN104717023A (en) * 2015-04-03 2015-06-17 上海航天测控通信研究所 Communication performance predictable 1553B bus engineering telemetric data acquiring method
CN106095717A (en) * 2016-06-27 2016-11-09 哈尔滨明快机电科技有限公司 A kind of dynamic retardation compensation method and device
CN106095717B (en) * 2016-06-27 2019-09-17 哈尔滨明快机电科技有限公司 A kind of dynamic retardation compensation method and device
CN106372027A (en) * 2016-08-31 2017-02-01 江苏茶花电气股份有限公司 Serial communication protocol of single chip microcomputer
CN109669372A (en) * 2018-12-24 2019-04-23 苏州谷夫道自动化科技有限公司 A kind of configuration method and device
WO2020134607A1 (en) * 2018-12-24 2020-07-02 苏州谷夫道自动化科技有限公司 Configuration method and apparatus
CN109669372B (en) * 2018-12-24 2021-01-19 苏州谷夫道自动化科技有限公司 Configuration method and device
CN110470343A (en) * 2019-08-29 2019-11-19 苏州艾铭森科技有限公司 A kind of iron-smelting furnace heat dissipation of exhaust fume monitoring system based on Modbus communications protocol
CN111245694A (en) * 2019-09-17 2020-06-05 浙江中自机电控制技术有限公司 Fault processing method based on Modbus extended communication
CN111327503A (en) * 2020-03-10 2020-06-23 浙江明度智控科技有限公司 MODBUS bus-based multi-master-station token scheduling device, communication method and system
CN111327503B (en) * 2020-03-10 2022-03-01 明度智云(浙江)科技有限公司 MODBUS bus-based multi-master-station token scheduling device, communication method and system
CN111683038A (en) * 2020-04-17 2020-09-18 许继集团有限公司 Fire alarm control system data processing method and device based on modbus protocol

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Application publication date: 20110511