Abstract: Introduction to the design and implementation of the optical disc servo control system for the control processor, μC / OS-II as a control processor, μC / OS-II as an embedded real-time operating system. This design can realize servo function of CD-ROM, CD-R / RW, and DVD, which is important for disc servo control systems, which has the advantages of easy maintenance, easy to expand, and is important for the implementation of drives and players that support multi-format discs. Reference value. The disc servo control system is a typical optical integration control system, an important part of the optical disk drive and the CD / VCD / DVD player. At present, the industry generally uses a single-chip microcomputer and servo control digital signal processor, which has been mononed (integrated with a single-chip microcomputer and servo control digital signal processor on a piece of chip) to implement the optical disc servo control system. Whether it is in the form of a chipset or a monolithic form, it is less than the control system with a board-level control software (also known as firmware). The currently employed solution is to implement a disc servo system using a small embedded operating system running on a single chip microcomputer. In order to use the self-developed disc servo signal processor to enable a servo control system that supports the multi-format disc, the author has a more in-depth study of the disc servo control system. This article describes the design and implementation of the optical disk servo control system for Hitachi, μC / OS-II as a control processor, μC / OS-II as an embedded real-time operating system. 1 Hardware Design CD Servo Control System of CD Servo Control System As shown in Figure 1. This design uses self-developed servo digital signal processors, Hitachi's H8S / 2357F high-performance 16-bit microcontroller, AKM's AK8566, TI SSI3736 and other chips to achieve CD-ROM, DVD and CD-R / RW Servo function. The verification of the design of the disc servo digital signal processor for self-developed disc servicular digital signal processor is completed in the system, which is prepared for the productization of the disc servo system. 2 Software design system analysis and software design of the disc servo control system is one of the difficulties achieved by the disc servo control system, and the advantages and disadvantages of the design are related to the system's readable disc, life, stability, scalability, maintenance and other performance. Because it is necessary to take into account DVD, CD, and CD-R / RW and other optical disk formats and various different mechanical parameters settings, the design of servo control software is relatively complicated. In order to make the control logic clearly and easy to implement, the CD servo control system running μC / OS-II on the H8S / 2357F is used is a better choice. The H8S / 2357F resources are relatively abundant, and the μC / OS-II can operate well on H8, which is easy to develop. The key to the design of the disc servo system is to analyze the disc servo system, build each function on the μC / OS-II core, so that it is organically coordinated to implement the disc servo control system. The communication and switching relationship between the subsystem of Figure 3 is 2.1 μC / OS-II embedded real-time multi-task operating system μC / OS-II is Jean J. One source code written by Labrosse is open to the free embedded real-time operating system. It is an upgraded version of μC / OS. From the oldest μCOS to the latest μC / OS-II, there have been a history of more than ten years. Its features mainly include: public source code, portability, curable, can be cut, support multitasking, with certainty, etc. μC / OS-II is a small and medium-sized embedded system, which is based on the priority preemptive real-time multi-task operating system, which includes real-time core, task management, time management, task communication synchronization (semapies, mailbox, message queue) and Memory management and other functions, most of the code is written in C language, written in assembly language with hardware related parts. When the application system works based on μC / OS-II, first initialize the CPU; then perform the operating system initialization, mainly complete the task control block (TCB) initialization, TCB priority table initialization, empty task creation, etc., then create new tasks And you can create additional new tasks in the newly created task; finally call the OSStart () function to start multiple task scheduling. 2.2 Analysis of the disc servo system for the design and implementation of the disc servo control system has some reference materials. According to the characteristics of μC / OS-II and the specific conditions of the optical disk servo system, the author will achieve the disc servo system into three running status: Power-on State, IDle State, Execution State (Execution state). Figure 2 shows the relationship between the set three states and the conditions that enters the respective states. In the three states, the execution state is most complicated. In order to simplify the complex problem, divide the execution state into three subsystems: Host Interface (HIS), Buffer Manager (BM), Disk Interface (DIS). Figure 3 shows the link between the three subsystems and the conditions that jump out of each subsystem. Figure 4 shows the state change between the subsystem and its conditions, which demonstrates the implementation process of the execution state. Figure 4 Task Status Running Relationship 2.3 Servo System The software structure of the servo system has been analyzed. After the disc servo system is initialized, five tasks have been created: Host Task, Serial Port Task, SERIAL Port Task, Disk Read Task, Disk Write Task, Servo Task (Servo Task). The task is inter-Semaphore and Mailbox, and the interactive control and task switching are implemented. Figure 5 shows the relationship between these five tasks. Figure 5 Task Structure Box Chart of Disc Servo System The framework of the master program: void main (void) {// Initialization processor and hardware ... // Produce task OSTASKCREATE (Servotask, (Void *) 0, (void *) & Servotaskstk [511], 4); OstaskCreate (viscwrtask, (void *) 0, (void *) & discwtaskstk [511], 6); ostaskcreate (discrdtask, (void *) 0, (void *) & discrdskstk [511], 8 Ostaskcreate (Hosttask, (void *) 0, (void *) & hosttaskstk3 [511], 10); ostaskcreate (serialcmdtask, (void *) 0, (void *) & Serialcmdtaskstk [511], 3); OstaskCreate (servotimertask, (void *) 0, (void *) & servotimertaskstk [511], 1); // Generate semaphore and task parameters ... // Task begins to run OsStart ();} This design is compiled on Hitachi's development system HEW2 Implementation, and is measured in verification system. The results show that the design can achieve the function of CD-ROM, DVD, and CD-R / RW, which is suitable for optical disk servo control systems, which have the advantages of facilitating maintenance, easy to expand. It has important reference value for the implementation of drives and players that support multi-format discs. Technology area
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