Design Of Embedded Operating System Based On Programable Logic Control Module

The programmable logical controller is a first floor control terrace in the industrial environment, facing to the control object directly. With the high reliability and easily extensibility,"the scope that it controls can be large or small, almost all the control domain; the object that it controls can be on-off signal,or analog signal,impulse signal, almost be all the control signal; it can be used in control, or as the data terminal,system diagnosis, almost all the project task", therefore the technology of the programmable logical controller and the technology of robot,the technology of CAD/CAM become three backbones in modern industrial automation. If the programmable logical controller can be open and provides the amity connects, it not only can be used in the gather spread control system,the field bus control system, and as the first floor controller combined with the nowadays network technique, but also be a kind of valid controller in the network terminal product.There is a very important terrace to manage system resources in the programmable logical controller CPU module, which is the embedded operate system. The applied program that the user writes will run under the support of the embedded operate system, and the function of the programmable logical controller is becoming strong just by the embedded operate system.The switch arithmetic is the first theories problem to resolve in developing embedded operating system. This arithmetic of robbing time slice combined with priority is the one that is adopted by the developed embedded operating system, and around the one, the relative questions are given clarification and testimony. How to design the time slice and assure the system to rob the CPU by the time slice, which is the first key that decides to succeed in developing the operating system or not.In the embedded operating system, the missions, task switch,task communication, memory management...etc, all need the corresponding data structures, such as the form, the stack, the brigade...etc., which support the data or the information that the operating system need. Therefore, we need to discuss the homologous data structure and arithmetic before design the embedded operating system.We can choose the layering type structure method or whole type structure method in designing the embedded operating system. This thesis adopts a whole type structure method. When adopt this method, the whole operating system is a heap of processes, and each process can call freely other process. Each process in the system need to be defined an entry, namely its entrance parameter and a return value, and call each other freely.When the kernel of the operating system switches tasks, it will depend on the state of tasks, and we can call this part Os_Task_Switch of system functions, namely a switcher. The switcher is the most hard-core as a kernel part of the operating system, and this thesis takes it as an emphasis, write the original program and give explanation.