Design And Implementation Of A General-Purpose Controller Based On Singlechip

Programmable logic controllers, also called programmable controllers or PLCs, are special-purpose computers used for industry control. They are easy to configure and program, foreseeable when running, and can keep working well even in tough industry environment. So PLCs are widely applied in industry control.On the basis of analyzing the architecture, principle and frequently used instructons of popular PLCs, a small general-purpose controller based on ADuC841 was designed in this paper, as a substitute for PLCs in some small control systems. This controller can be configured and program in a more flexible way, and reduced the cost largely on the premise of good reliability.In repect of hardware design, the system introduced in this paper designed plenty of peripheral equipment based on ADuC841 according to the architecture of PLCs, realized most of the necessary modules of PLCs, including CPU(Central Process Unit), digital I/O, analog I/O, serial port communication, human-machine-interface, and so on. Special process circuit is designed for I/O device, which enhanced the system's ability for anti-interference and drive. As to software, in order to enable the system to implement the PLC instructions, first a coding table was designed on the basis of studying the frequently used PLC instructions and analyzing it's characteristic. And then a PC software and singlechip software was developed respectively, the former code the user program and send it to the singlechip, and the latter receive the data, decode it, and call corresponding C51 functions to conduct the PLC instructions. The PC software is developed with LabVIEW, and the singlechip software with Keil C51. On the basis of analyzing the principle of PLCs, the controller system software is developed to imitate the working of PLCs. And the embedded real-time operation system was transplanted to the singlechip, which simplized the work of task management and enhanced the reliability of the software. Corresponding to PLC instructions, a set of C51 functions was developed to realize the conduct of user program. The singlechip system communicated with PC by serial port, which support the user program's downloading and data exchange between singlechip and PC.The design of this embedded controller based on singlechip ADuC841 comply with the trend of the development of industry control, provide a more flexible way to develop control system, and reduced the cost largely, possesses high practical value.