A module structure real-time operating system for microcomputers

With the advent of large-scale and complicated microcomputer application systems, the role of OS is becoming more important. An OS which can cope with various application requirements is strongly desired. This paper aims at the construction of OS which can be made optimum for various real-time applications. A construction of real-time modular structure OS using the microcomputer 68000 is proposed. The message-passing and procedure-call schemes are combined to connect the modules. A two-layered hierarchy module structure is proposed, suppressing the increase of the overhead due to modular implementation, and also providing the flexibility for replacing modules. By this scheme, operating systems with capacity from 10 KB to 150 KB can be constructed, covering a wide range of applications from a small-scale system with hardware built-in structure to the relatively large-scale system requiring programming functions, by simply modifying the combination of modules. To utilize commercial softwares or general-purpose OS in the real-time environment, a scheme is proposed in which the general-purpose OS is executed as the secondary OS with the real-time kernel. As a result of evaluation, when a general-purpose OS, CP/M-68K, is executed as the secondary OS, the processing time is increased by 12.7% compared with CP/M-68K directly implemented on the 68000.