| 摘要 |
PROBLEM TO BE SOLVED: To provide a dual-processing unit with single clock source CPUs and I/O module having a safety timer crosscheck diagnostic to enable each CPU to verify the accuracy of the clock source of the other CPU. SOLUTION: The diagnostic works by having the first CPU act as a controlling CPU and the second CPU act as a monitoring CPU. Both CPUs are synchronized to begin one cycle of their respective safety functions at the same time. As part of the diagnostic, the controlling CPU is set to be interrupted after a pre-determined time period while the monitoring CPU is set to be interrupted slightly after that. When the controlling CPU is interrupted after the pre-determined time has passed as determined by that CPU's clock source, the controlling CPU sends a signal to the monitoring CPU and the monitoring CPU verifies that the perceived time is within an expected range. COPYRIGHT: (C)2008,JPO&INPIT
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