Design And Realization Of The Programmable Controller (PLC) Running System

As a very important basic equipment, Programmable Logic Controller(PLC) is called one of the three major pillars in Automation Industry. PLC plays more and more important role in the field of industry manufacture. Foreign PLCs has hold the Chinese market for all these years, which is unacceptable. Chinese study on PLC should not only keep in the state of digestion of foreign technology. IEC61131-3 is issued just in time, which offered a standard for PLC programming language. That offers domestic PLC researchers a chance to compete with foreign PLC companies in software design. And the development of high performance single chip make it possible for us to overtake foreign PLC researchers in hardware design.Under those conditions, it is very imperative for us to develop a new-type PLC of our own following international standard. So we put forward the project "Research on New-type PLC Based on IEC61131-3", which is sponsored by the science & technology fund of Beijing Education Committee (Project Number:2002kj026).Based on the comparison of two designs used by domestic and international experts on PLC, the paper presents the design plan for new-type PLC system based on IEC61131-3 . The whole system consists of three parts: (1)hardware system design(2)the design of integrated development environment(3)the design of PLC running system based on C51 and the design of program downloading interface. The author has mainly designed the third part: the design of the PLC running system. Comparing different PLCs, the author analyzed and summarized the working principle of normal PCLs and designed a running system using C51 for our own PLC. This PLC running system is a least system on our self-designed circuit board. The method for realization of the system is presented in detailed in this paper. Based on the study of IEEE1149.1, the author designed a JTAG parallel adapter. Programmed with C, the parallel port is controlled to generate JTAG sequence. Then the TAP state machine for JTAG is realized through program based on JTAG sequence Then with the operations of the flash registers for C8051f020, access to FLASH ROM is realized. DLL(Dynamic Link Library) program for access to FLASH ROM is build Using the IDE Visual C++.Two PLC application examples are designed to test the function of the PLC system: control of flash light and control of traffic light. The pictures of the results for the tests are given in the paper.The whole system is just a rudiment of the mini-type PLC, so there are much work to do to apply this PLC in practice. And this paper has offered beneficial attempts for the development of homemade PLCs.