| 摘要 |
PURPOSE:To improve efficiency in the self diagnosis of a CPU, and to easily diagnose the failure of an external bus unit, by providing a program memory connected directly to a central processing unit CPU. CONSTITUTION:While the program of a CPU1 is operated, it is controlled so that a CPU bus is not affected by buffers 4 and 5. On a memory 10, programs for the check of the CPU 1, and the check for the content of the program memory are written. Next, diagnostic programs for a program memory 6, a working memory 7, and an interface circuit 8, connected to an external bus, are written. Since it is possible to operate the diagnostic function of the CPU1 even when some failure is generated in a circuit connected to the external bus, it can be outputted to a diagnostic status output 12 in which diagnostic operation is generated an abnormal state.
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