CHAPTER 1 OVERVIEW
The RI600PX is a built-in real-time, multi-task OS that provides a highly efficient real-time, multi-task environment to increases the application range of processor control units.
The RI600PX is a high-speed, compact OS capable of being stored in and run from the ROM of a target system.
The RI600PX is based on the
mITRON4.0 specification. Furthermore, the RI600PX supports the memory protection function specified by
mITRON4.0 protection extension.
Control equipment demands systems that can rapidly respond to events occurring both internal and external to the equipment. Conventional systems have utilized simple interrupt handling as a means of satisfying this demand. As control equipment has become more powerful, however, it has proved difficult for systems to satisfy these requirements by means of simple interrupt handling alone.
In other words, the task of managing the order in which internal and external events are processed has become increasingly difficult as systems have increased in complexity and programs have become larger.
Real-time OS has been designed to overcome this problem.
The main purpose of a real-time OS is to respond to internal and external events rapidly and execute programs in the optimum order.
A "task
" is the minimum unit in which a program can be executed by an OS. "Multi-task
" is the name given to the mode of operation in which a single processor processes multiple tasks concurrently.
Actually, the processor can handle no more than one program (instruction) at a time. But, by switching the processor's attention to individual tasks on a regular basis (at a certain timing) it appears that the tasks are being processed simultaneously.
A multi-task OS enables the parallel processing of tasks by switching the tasks to be executed as determined by the system.
One important purpose of a multi-task OS is to improve the throughput of the overall system through the parallel processing of multiple tasks.
1.1.3 Memory protection function
1 ) High-reliability system
To reduce a possibility of being unable to detect program glitches when debugging the program and causing a trouble in the market after the system has been shipped from the factory, this OS assures the system of high reliability.
If memory data destruction occurs especially in a memory area in which the OS, etc. are stored, the system may produce a dangerous condition by, for example, operating erratically. However, since this OS is free of memory data corruptions, the system can continue operating normally, and is therefore assured of high system reliability.
2 ) Debug assistance
In systems without memory protection, a corruption of memory content by an illegal pointer behavior, etc. generally is not noticed until it actually comes to the surface as a trouble symptom. The cause of the trouble can only be identified by analyzing emulator's trace data, which requires a large amount of time. The RI600PX can detect a bug when an illegal memory access is committed, enabling the debugging efficiency to be greatly increased.