CN101262486B - Modbus bus analysis system based on built-in platform - Google Patents

Abstract

The Modbus bus analysis system based on the embedded platform belongs to the field of analysis technology of devices or networks following the Modbus bus protocol. Software modules for analysis and analysis software modules interconnected through configuration file analysis and interactive software modules; communication sub-boards include 10M Ethernet ports using chip CS8900, the first DB9 serial port using chip MAX232, and the first DB9 serial port using chip 488 Two DB9 serial ports; the core board is connected with the backplane bus of the Modbus analysis device motherboard through the SO-DIMM interface and the communication sub-board respectively, and the communication between the core board and the communication sub-board is realized by the motherboard. The analysis device can be respectively connected with the upper computer and the Modbus device or network to be analyzed in the serial link mode, and can also be realized through Ethernet in the TCP/IP mode. The invention fills up the gap in the existing technology related to Modbus bus analysis.

Description

Modbus Bus Analysis System Based on Embedded Platform

technical field

The invention relates to an analysis system and an analysis method based on an embedded platform, in particular to an analysis system and an analysis method applied to Modbus bus equipment.

Background technique

Related technical references are as follows:

In terms of patents, through the patent search platform of the State Intellectual Property Office, it is found that the related research on the Modbus protocol is focused on the realization of the protocol itself and the conversion between the Modbus protocol and other protocols. At present, no new inventions and applications of Modbus equipment analysis related devices have been found.

The existing 6 invention patents and 1 utility model patent related to the Modbus protocol are as follows:

1 Protocol Conversion Method and Device Between Modbus/TCP Industrial Ethernet and DeviceNet Fieldbus 2 Protocol conversion method and device between Modbus/TCP industrial Ethernet and Profibus DP field bus 3 Multi-protocol conversion method and device between Modbus/TCP industrial Ethernet, equipment network field bus and Profibus DP field bus 4 A protocol conversion method between Modbus and DeviceNet 5 Interface module for Modbus device network and Fieldbus device network 6 System and method capable of generating Modbus CRC errors and comparing and displaying errors 7 Modbus Network Interface Converter for Programmable Controllers

In terms of academic papers, through the cross-database search engine of Tsinghua University, it is found that the relevant research on the Modbus protocol is focused on the protocol itself, or the improvement of the protocol itself, or its implementation on a certain hardware platform. The analysis method and system development and research of bus equipment.

Between 1979 and 2008, the literature records with "Modbus" in the title are as follows:

1 China Journal Network 300 pieces 2 China Excellent Master's Dissertation Full-text Database 25 pieces 3 China's important conference full-text database 14

4 China Doctoral Dissertation Full-text Database 0 5 China's important newspaper full-text database 0 Total 339 items

The above 339 literature records can be divided into four categories: the realization of the Modbus protocol on the embedded system, the application of the Modbus protocol, the conversion between Modbus and other protocols, and the research on the protocol itself. At present, no methods involving the analysis of Modbus devices have been found. Discussion and related research literature.

At present, the development and debugging process of Modbus equipment and the online detection during the operation of Modbus equipment have an urgent demand for the analysis method of Modbus bus equipment and related devices.

Contents of the invention

In order to meet the needs of the current development of Modbus bus equipment and the online analysis of Modbus bus equipment, and to fill the market vacancy, the present invention utilizes the existing embedded system technology to develop a Modbus bus equipment analysis system. The analysis system is based on Samsung S3C2410 hardware platform and embedded Linux operating system, and implements and expands a complete Modbus bus protocol stack for analysis requirements. On this basis, a set of analysis strategies has been independently designed, with configurable manual and automatic analysis functions. And combined with the embedded open source Web Server software platform boa, the embedded Web server is constructed as the human-computer interaction interface of the analysis system to realize the setting of the analysis system's working mode, parameters to be analyzed, function code types and Modbus data frame content.

The Modbus industrial control bus protocol involved in the present invention complies with the GB/Z 19582.1-2004 national standard, which is proposed by the China Machinery Industry Federation, the Institute of Comprehensive Technology and Economics of Machinery Industry Instrumentation, Schneider Electric (China) Investment Co., Ltd., etc. Drafted jointly by the company and research institutions. This standard is used as a communication link standard for industrial automation equipment. It uses the application layer message transmission protocol in the Open System Interconnection OSI model to provide client/server communication between devices connected to different types of buses or networks. The national standard Modbus protocol is divided into three parts: the Modbus application protocol, the implementation guide of the Modbus protocol on the serial link, and the implementation guide of the Modbus protocol on the TCP/IP, as shown in the bold black box in Figure 1 respectively.

The analysis object of the Modbus analysis system of the present invention is the Modbus device based on the above-mentioned protocol standard or the network composed of Modbus devices.

The present invention is characterized in that:

The Modbus bus device is a device that adopts the application layer message transmission protocol in the open system interconnection model OSI to provide client/server communication between devices connected to different types of buses or networks. The analysis system Contains: Modbus bus equipment analysis system motherboard, core board and communication daughter board, of which:

The core board, including the central processing unit S3C2410 and the memory and flash memory connected to it, are jointly connected with the backplane bus of the Modbus bus device analysis system master board through the SO-DIMM interface, wherein:

The flash memory hosts software modules for analysis and software modules for interaction in the case of power-down, where:

The analysis software module is used to communicate with the bottom Modbus data frame of the analyzed Modbus bus device, and the analysis software module includes an embedded Linux operating system, a Modbus bus software protocol stack, and a master station and a slave station management unit, wherein :

The embedded Linux operating platform is constructed for the central processing unit S3C2410, and is used to manage the entire hardware device resources and framework of the analysis system;

The Modbus bus software protocol stack is used to comprehensively analyze the responses of Modbus bus devices and networks to various different types of data frames, and the Modbus bus software protocol stack is interconnected with the embedded Linux operating system through a hardware resource access interface;

The master station and the slave station management software unit complete the analysis of the configuration file generated by the interactive software module, the analysis of the Modbus communication data frame, and the statistical generation of the record and analysis data, and communicate with the Modbus bus through the frame data interface Software protocol stack interconnection;

The analysis software module runs in sequence as follows:

Step (1), first find the configuration file in the corresponding position of the flash memory, analyze the configuration file and configure the relevant hardware interface of the analysis system, the configuration file is stored in the flash memory by the host computer through the interactive software module middle;

Step (2), according to the configuration information in the configuration file, run the corresponding analysis strategy, start analysis;

Step (3), recording and parsing the analysis results, forming a result file in a predetermined format and storing it in the corresponding position of the flash memory, and uploading it to the host computer by the interactive software module;

The software module for interaction is used for the upper computer to use a general-purpose Internet browser to interact with the analysis system, to provide the operator of the upper computer with a man-machine interface for configuring the underlying communication parameters and analysis strategies, and to communicate between the operator and the underlying software. Provide parameters and results, the interactive software module includes: embedded web server boa, and cgi web page script, wherein:

The embedded web server boa is used to set up web page services;

The cgi webpage script runs on the boa, and is used to provide the operator with a webpage-type human-computer interaction interface. The cgi webpage script is interconnected with the embedded web server boa through the two interfaces of user configuration and analysis results;

This interactive software module is loaded into the internal memory after the hardware device is initialized by the Linux operating system and automatically operates according to the following steps:

Step (A), responding to the configuration of the analysis system hardware interface by the host computer, receiving the configuration file submitted by the host computer and storing it in the flash memory;

Step (B), according to the configuration of the host computer, start the corresponding software module for analysis;

Step (C), uploading the analysis results in step (B);

Communication daughter board, including: 10M Ethernet port, the first DB9 serial port and the second DB9 serial port, of which:

The 10M Ethernet interface adopts the chip CS8900 to realize the physical layer of the TCP/IP protocol stack and the MAC layer of the medium access control layer;

The first DB9 serial port, working under RS232 protocol, adopts MAX232 and DB9 interface,

The second DB9 serial port works under the RS485 protocol, using MAX488 chip and DB9 serial port;

The 10M Ethernet port, the first DB9 serial port, and the second DB9 serial port are jointly connected to the backplane bus of the motherboard through the PC104 bus, and the communication between the communication sub-board and the core board is supported by the motherboard.

In the serial link mode, the analysis system is connected with the host computer and the Modbus device or network to be analyzed in the following manner:

The 10M Ethernet port is connected to the host computer via a network device, and is used for operators to remotely operate and set the analysis system through the configuration interface,

The second DB9 serial port is connected with the 485 bus of the Modbus device to be analyzed or the network, and is used to complete the Modbus protocol communication with the Modbus device to be analyzed or the network in the serial link mode.

The first DB9 serial port is used as the bottom-level debugging interface of the analysis system, and outputs the relevant operating information of the Linux operating system platform of the analysis system, and the first DB9 serial port is connected with the host computer through the RS232 serial port. In the analysis system When it fails to work normally, the operation information output by the first DB9 serial port can also be used for diagnosis and debugging.

In TCP/IP mode, the analysis system is connected to the Modbus device or network to be analyzed and the host computer in the following manner:

The 10M Ethernet port is respectively connected to the upper computer and the Modbus device to be analyzed or the network through the network equipment.

The invention fills the blank of Modbus bus equipment or network environment analysis system.

The advantages of the present invention are:

1. Using the existing embedded system technology, the Modbus analysis system with complete functions has been realized, filling the gap in the market;

2. On the basis of the standard Modbus protocol stack, the protocol has been expanded and transformed for different analysis requirements, so that the flexible configuration and judgment of the Modbus data frame at the link layer can be realized;

3. Based on the standard Modbus to realize the analysis function, the system can analyze a single device offline, and can also analyze the entire running Modbus network online;

4. The use of embedded Linux operating system is conducive to enriching functions and upgrading products;

5. With the installation of the embedded server boa, the analysis results only need to use the web browser on the host computer, which can be viewed locally or remotely, making the acquisition of the analysis results very flexible and convenient.

Description of drawings

Figure 1. The basic structure of the national standard Modbus protocol;

Figure 2. Modbus analysis system hardware structure block diagram;

Figure 3. The overall block diagram of the analysis system software structure;

Figure 4. Based on the serial link mode, the signal connection between the analysis system and the host computer and the analyzed object;

Figure 5. Based on the TCP/IP mode, the signal connection between the analysis system, the host computer and the analyzed object;

Figure 6. Based on the serial link mode, analyze the system software and data interface flow;

Figure 7. Analysis system software and data interface flow when based on TCP/IP mode;

Figure 8. Schematic diagram of the analysis strategy of the master station;

Figure 9. Schematic diagram of the analysis strategy of the slave station;

Figure 10. Schematic diagram of the frame parsing process;

Figure 11. Schematic diagram of the result processing process.

Specific implementation

As shown in Figure 2, the hardware of the analysis system consists of three parts: the core board, the communication sub-board and the motherboard. The core board is connected to the motherboard through the SO-DIMM interface, and the communication sub-board is connected to the motherboard through the PC104 interface. Such a multi-layer structure is convenient for hardware design, debugging and upgrading. The core board includes three parts: central processing unit (CPU), memory (RAM) and flash memory (Flash). The manufacturers and models are: Samsung S3C2410, Hynix HY57V551620CT-H, SamsungK9F1208U0B. The communication daughter board has a 10M Ethernet port and two full-featured serial ports. The Ethernet interface chip adopts Crystal's CS8900, which internally uses logic gate circuit hardware to realize the contents of the physical layer and MAC layer of the TCP/IP protocol stack; serial port 1 works under the standard RS232 protocol, and uses MAX232 and standard DB9 interface to realize ;Serial port 2 is used to expand the support of the equipment to be analyzed and the network, works under the RS485 protocol, and is realized by the MAX488 chip and the DB9 interface. The communication line between the core board and the communication daughter board is supported by the motherboard. The entire analysis system adopts a multi-level plug-in structure of core board, communication sub-board, and motherboard, which is conducive to the development of Modbus analysis system and the upgrading of software and hardware.

The soft modules of the analysis system include two parts: software modules for analysis and software modules for interaction. The analysis software module is mainly used to communicate with the underlying Modbus data frame of the equipment to be analyzed, including the embedded Linux operating system platform, Modbus bus software protocol stack, master station and slave station management for managing the hardware device resources and framework of the entire analysis system Software unit; interactive software modules are mainly used to provide operators with an upper-level man-machine interface for configuring underlying communication parameters and analysis strategies, and for transferring parameters and results between operators and underlying software, mainly including embedded Web services for setting up Web pages. The server boa and the cgi webpage script running on the boa are used to provide the operator with a webpage-style human-computer interaction interface. The two software modules work on the bottom layer and the upper layer respectively, and data interaction is carried out through the configuration file of the specified format in the middle. The overall framework of the software is shown in Figure 3.

Both of these software modules are resident in flash memory when powered down. When the analysis system is powered on, the Linux operating system will first transfer the interactive software modules into the memory to run automatically after initializing the hardware devices. When the interactive software module is started, the host computer can interact with the Modbus analysis system using a common Internet browser. The interactive software module mainly completes the following functions: 1) Respond to the various configurations of the host computer to the Modbus analysis system hardware interface (mainly the serial port), receive the configuration files submitted by the host computer, and finally save all configurations in the form of files in the flash memory Middle; 2) Start the corresponding analysis software module according to the configuration of the host computer; 3) Manage and upload the analysis results. After the analysis software module is started, it mainly completes the following functions: 1) first find the configuration file in the corresponding location of the flash memory, parse and configure the relevant hardware interface of the analysis system; 2) run the corresponding software according to the configuration information in the configuration file Analyze the strategy and start the analysis; 3) record and analyze the analysis results, write the analysis results into a result file in a predetermined format and save it in the corresponding location of the flash memory, and the interactive module is responsible for uploading.

The Linux operating system platform used in the analysis software module is an embedded Linux operating system built on the basis of the standard Linux kernel and optimized and transplanted for the S3C2410 embedded hardware platform used in the analysis system. Because the Linux operating system has the advantages of high execution efficiency, rich software resources, and convenient development, it can flexibly realize the overall software structure of the Modbus bus analysis system by combining independent programming development and building third-party support software.

The Modbus bus protocol stack in the analysis software module is completely independently realized by C language code, running on the application layer of the Linux operating system, and according to the needs of detailed analysis of the communication status of the link layer of the protocol stack, based on the standard Modbus protocol stack The modified protocol stack can be flexibly configured for the Modbus link layer data frames and configurations according to the analysis needs of users, so as to achieve a comprehensive analysis of Modbus devices and networks for various types of data frames. The purpose of responding to the situation.

The uppermost layer of the analysis software module is the master station and the slave station management software unit. This part is completely independently designed and developed. It mainly completes the analysis of the configuration file generated by the interactive software module, the analysis and recording of the Modbus communication data frame and Statistical generation of analysis results.

In terms of interactive software modules, we use an embedded web server based on the software and hardware system platform of the analysis system, and the host computer uses a browser to access the web page provided by the analysis system to realize the configuration of the working mode and parameters of the analysis system by the user. The embedded web server platform adopted is boa, an open source web server widely used in the Linux environment. It has the advantages of simple structure, less hardware resource occupation, and high execution efficiency. It is very suitable for building a web server on the embedded Linux platform. On this basis, we use the cgi script language to program the web page configuration interface unit of the analysis system.

The software module of the analysis system realizes manual and automatic analysis. And corresponding to the different working modes stipulated in the national standard Modbus protocol (including TCP/IP mode, Ascii mode on the serial link and RTU mode), the software module realizes the corresponding analysis strategy to meet the analysis needs.

As shown in Figure 4, when the serial link mode is selected to analyze the object to be analyzed, the analysis system is connected to the host computer through the Ethernet interface of the communication sub-board, which is used for the analyst to use the configuration interface to remotely operate and set the analysis system. The specific connection method can be connected to the upper computer via a local area network or the Internet. The serial port 2 of the analysis system working under the RS485 protocol is connected to the 485 bus interface of the device to be analyzed or the network, and is used to complete the Modbus protocol communication with the device to be analyzed or the network in the serial link mode. The serial port 1 working under the RS232 protocol is used as the underlying debugging interface of the analysis system, and outputs the relevant operating information of the Linux operating system platform of the analysis system. When the software or hardware of the analysis system cannot work normally, the developer can connect the serial port 1 to the RS232 serial port of the upper computer, and use the system operation information output by the analysis system serial port 1 to diagnose and debug the equipment.

In the working state of the analysis system, the operator uses the web browser of the host computer to access the configuration web page of the interactive software module of the analysis system through the Ethernet port, directly specifies the working mode of the analysis system on the web page, and fills in relevant configuration parameters and links Layer frame data is passed to the analysis system. The relevant configuration parameters submitted by the user are saved by the webpage script in the form of a configuration file, and the analysis software module is started. The analysis software module stored in the Flash memory is read into the memory by the Linux operating system, and the central processing unit reads and runs the software code in the memory. The analysis software module obtains various related configurations of the protocol communication process by the user by reading the configuration file created by the webpage script, and sets the physical link parameters according to the configuration, and encapsulates the Modbus link layer data frame in the specified format. Then start the communication process with the Modbus device. In the serial link mode, the Modbus protocol communication process is completed by the protocol stack communication part in the analysis software module through the RS-485 serial link between the analysis system and the device. After the analysis system completes the communication of a data frame, it needs to record the communication with the device to be analyzed, which is used for statistics and viewing of the analysis results after the analysis is completed. After completing a complete analysis process specified by the user, the analysis software module needs to perform statistics and analysis on the obtained analysis results, and calculate the number of Modbus data frame communications completed by the device to be analyzed, the number of wrong data frame communications, and the number of lost data frames The number of times and other related statistics, the obtained results are saved in the result file for use by the interactive software module. The interactive software module reads the result file and returns it to the user in the form of a result web page. The software execution flow is shown in Figure 6.

When the object to be analyzed is selected to be analyzed in TCP/IP mode, the hardware connection between the analysis system and the host computer and the object to be analyzed can be completed by using the Ethernet port. Since the Modbus protocol belongs to the application layer protocol, and its layer is above the TCP/IP protocol, the hardware connection mode of the Ethernet port can be very flexible. You can choose to connect directly to the host computer and the object to be analyzed through the network interface, or It can be connected to the host computer and the object to be analyzed through a general network interface through a local area network or even the Internet. As shown in Figure 5.

When the analysis system works in TCP/IP mode, its basic software structure and working mode are not substantially different from those in serial link mode. Only the physical link with the device to be analyzed has been changed to an Ethernet interface, and due to the change of the physical link, the analysis software module must not only handle the sending and receiving of Modbus protocol data frames and the protocol stack state machine, but also have the ability to understand TCP In /IP mode, analyze the access control capability of the TCP socket connection between the system and the object to be analyzed. The software execution process in TCP/IP mode is shown in Figure 7.

The analysis environment and analysis content that the Modbus analysis system involved in the present invention can adapt to include:

1. When the object to be analyzed works in RTU or ASCII mode, various working conditions corresponding to different physical link settings.

2. The data processing and adaptability of the object to be analyzed to various types and forms of Modbus request frames and response frames.

3. Under the TCP/IP working mode, the object to be analyzed has the access control ability to the TCP socket connection.

4. The stability of the object to be analyzed under different link operating conditions.

According to the different working modes between the analysis system and the equipment to be analyzed, the analysis strategy implemented by the analysis system is divided into two parts: the analysis strategy under the master station working mode and the analysis strategy under the slave station working mode, corresponding to the analysis system as the There are two situations: the master station, the device to be analyzed as the slave station and the analysis system as the slave station, and the device to be analyzed as the master station.

When the analysis system is used as the master station, the analysis strategy adopted is shown in Figure 8. After power-on, the analysis system first starts the Linux operating system, and calls a driver module to initialize the hardware device. After completing the operating system boot process, the analysis system runs interactive software modules (based on the embedded web server). In this way, the analyst can set the working parameters of the analysis system and start the analysis process through the configuration page on the host computer. After the operator configures the working parameters and analysis data of the analysis system, the configuration page saves the user's configuration data to the specified configuration file, and then starts the underlying analysis software module. The underlying software obtains user configuration parameters by reading and parsing the relevant parameter fields of the configuration file, configures and sets the corresponding hardware interface according to these parameters, and constructs a data frame for analysis. After that, the analysis system sends a Modbus request frame to the device to be analyzed in the way specified by the user, and waits for the response of the device to be analyzed. According to the different response frames returned by the equipment to be analyzed, the analysis system records the communication status of each frame. After completing the number of frame communications specified by the user, the analysis system will count and analyze the analysis results according to the recorded communication status, and save the analysis results as a result file in a specified format. The content of protocol frame analysis includes: judging whether the current link has transmitted a complete data frame; extracting the function code field in the data frame, judging whether the function code in the received data frame is a valid function code, and whether it is an analysis system The function code being analyzed; extract the data content field in the data frame, and judge whether it is consistent with the expected data content of the analysis system; calculate the LRC check code according to the content of the data frame, and compare it with the LRC check byte at the end of the data frame Compare to determine whether there is an error in the data frame transmission process. The content of the analysis result processing includes: calculating the total number of frames received during the analysis process, and comparing it with the frame communication times specified by the user to obtain the number of lost frames; counting the number of error frames caused by illegal function codes; The number of error frames caused by errors such as LRC check error and data content error; calculate the number of correct frames that successfully complete the communication.

See Figure 10 and Figure 11 for the detailed flow of frame analysis and analysis result processing. The web server creates an analysis result page according to the result file generated by the protocol stack communication software, for analysts to view the analysis result. Taking the Ascii mode on the serial link as an example, the frame analysis process can decompose a received frame according to the structure shown in Table 1, and then analyze and obtain corresponding statistical data according to the process in Figure 10 .

start address function code data LRC check Finish 1 character 2 characters 2 characters 0 to 2×252 characters 2 characters 2 characters

Table 1 Modbus data frame structure

When the analysis system is used as a slave station, the basic process of its analysis strategy is similar to that of the master station, except that in the process of communication between the analysis system and the device to be analyzed, the analysis system waits for the Modbus request frame from the device to be analyzed, and sends The device to be analyzed returns a response frame. The specific analysis strategy process is shown in Figure 9.

Claims (3)

1. Based on the Modbus bus analysis system of the embedded platform, it is characterized in that the Modbus bus equipment is a kind of application layer message transmission protocol in the open system interconnection model OSI, which is connected to different types of bus or network equipment. Client/server communication equipment, the described Modbus bus analysis system contains: Modbus bus analysis system motherboard, core board and communication sub-board, wherein: The core board, including the central processing unit S3C2410 and the memory and flash memory connected to it, are jointly connected with the backplane bus of the Modbus bus analysis system motherboard through the SO-DIMM interface, wherein: The flash memory hosts software modules for analysis and software modules for interaction in the case of power-down, where: The analysis software module is used to communicate with the bottom Modbus data frame of the analyzed Modbus bus device, and the analysis software module includes an embedded Linux operating platform, a Modbus bus software protocol stack, and a master station and a slave station management unit, wherein : The embedded Linux operating platform is constructed for the central processing unit S3C2410, and is used to manage the entire hardware device resources and framework of the analysis system; The Modbus bus software protocol stack is used to comprehensively analyze the response of Modbus bus equipment and network to various different types of data frames, and the Modbus bus software protocol stack is interconnected with the embedded Linux operating platform through a hardware resource access interface; The master station and the slave station management unit complete the analysis of the configuration file generated by the interactive software module, the analysis of the Modbus communication data frame, and the statistical generation of the record and analysis data, and communicate with the Modbus bus software through the frame data interface Protocol stack interconnection; The analysis software module runs in sequence as follows: Step (1), at first find configuration file in flash memory corresponding position, analyze this configuration file and configure the relevant hardware interface of described Modbus bus analysis system, described configuration file is that upper computer is saved in place by described interactive software module in the flash memory; Step (2), according to the configuration information in the configuration file, run the corresponding analysis strategy, start analysis; Step (3), recording and parsing the analysis results, forming a result file in a predetermined format and storing it in the corresponding position of the flash memory, and uploading it to the host computer by the interactive software module; The interactive software module is used for the upper computer to use the general Internet browser to interact with the Modbus bus analysis system, to provide the operator of the upper computer with a man-machine interface for configuring the underlying communication parameters and analysis strategies, and to communicate between the operator and the underlying software. Parameters and results are provided between, the interactive software module includes: embedded web server boa, and cgi webpage script, wherein: The embedded web server boa is used to set up web page services; The cgi webpage script runs on the boa, and is used to provide the operator with a webpage-type human-computer interaction interface. The cgi webpage script is interconnected with the embedded web server boa through the two interfaces of user configuration and analysis results; This interactive software module is loaded into the memory after the hardware device is initialized on the Linux operating platform and automatically operates according to the following steps: Step (A), in response to the configuration of the host computer to the hardware interface of the Modbus bus analysis system, receive the configuration file submitted by the host computer and store it in the flash memory; Step (B), according to the configuration of the host computer, start the corresponding software module for analysis; Step (C), uploading the analysis results in step (B); The communication sub-board includes: 10M Ethernet port, the first DB9 serial port and the second DB9 serial port, wherein: the 10M Ethernet port adopts the chip CS8900 to realize the TCP/IP protocol stack physical layer and the media access control layer MAC; The first DB9 serial port, working under the RS232 protocol, adopts MAX232 chip and DB9 interface, The second DB9 serial port works under the RS485 protocol, using MAX488 chip and DB9 serial port; The 10M Ethernet port, the first DB9 serial port, and the second DB9 serial port are jointly connected to the backplane bus of the motherboard through the PC104 bus, and the communication between the communication sub-board and the core board is supported by the motherboard. 2. the Modbus bus analysis system based on embedded platform according to claim 1, is characterized in that under the serial link pattern, described Modbus bus analysis system and described upper computer and Modbus equipment to be analyzed or network are as follows Way to connect: The 10M Ethernet port is connected to the host computer through the network equipment, and is used for operators to remotely operate and set the Modbus bus analysis system by using the configuration interface. The second DB9 serial port is connected to the 485 bus of the Modbus device to be analyzed or the network, and is used to complete the Modbus protocol communication with the Modbus device to be analyzed or the network in the serial link mode, Described first DB9 serial port is as the bottom debugging interface of described Modbus bus analysis system, outputs the relevant operation information of the Linux operating platform of described Modbus bus analysis system, and described first DB9 serial port is connected with upper computer by RS232 serial port, in place When the analysis system fails to work normally, the operation information output by the first DB9 serial port can also be used for diagnosis and debugging. 3. the Modbus bus analysis system based on embedded platform according to claim 1, is characterized in that under TCP/IP mode, described Modbus bus analysis system is connected with Modbus equipment to be analyzed or network and upper computer in the following manner: The 10M Ethernet port is respectively connected to the upper computer and the Modbus device to be analyzed or the network through the network equipment.

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