| Programmable Logic Controller (PLC) is essential for industrial control system, which is the core of control system. In other countries, the traditional PLC technology has been developed and applied for decades, and the technology is relatively mature and perfect. In our country, although the research and application of PLC technology has also experienced many years, the core technology standards has been under the control of foreign companies and we can not form our own technological superiority, which resulted in the PLC market, domestic companies have long been the monopoly of a few countries, the price of PLC equipment is high which affect the development of national industries to some extent.At the same time, the entire electronics industry is developed rapidly. There are many high-performance, low power, low-cost micro-controller in the market. Microprocessor-based embedded applications have also been all over the world corner. The current microprocessor performance has been very good, microprocessor-based embedded devices are fully competent to most of the industrial automation and control requirements. In this context, Shandong Computing Since Center has research and developed high-performance embedded PLC, which is based on ARM core. The PLC board adopted a CAN bus structure, the function has a very good scalability. The series has now been achieved with the application of the product shape, and can support RS-232, RS-485, RJ45, USB and other interfaces of the communication link. However, it is not prepared to present some popular communications bus protocol, such as Modbus, profibus; witch hampered the promotion of the product to some extent.In order to improve the performance of ShanKe PLC,based on the analysis of embedded systems and the Modbus communication protocol, the paper designed communication scheme for ShanKe PLC's Modbus.In order to achieve this program,firstly, I built my own embedded development platform for communication research. The entire development platform consists of hardware and software systems of two parts:the hardware system is the use of the ARM Embedded System development board, and it's control center is produced by Philips LPC2000 microprocessor based on ARM micro-controller chip; The software system is mainly based on PC-related development tools and the development board transplantationμC /OS-II real time operating system. Finished the embedded development system source code for communications design and test work, again successfully transplanted to the part of the source device shangke PLC, and ultimately the shangke PLC RTU communication protocol of Modbus slave mode support work.The paper designed shangke PLC of the Modbus communication program source code is all done using C language; therefore, the source code has good performance and efficiency. At the same time, this communication scheme can be easily applied to the other instrumentation of shangke. So it has great practical significance for series of ShanKe equipment applications. |
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