| 摘要 |
PURPOSE:To improve the fail-safe performance of an arithmetic processing unit within a controller by performing a self-diagnosis through an arithmetic processing part to check the memory contents of other arithmetic processing parts, and detecting the generation of a fault together with the decision of a faulty area based on the result of said self-diagnosis. CONSTITUTION:ROM13 and 14 store the self-diagnosis programs for CPU11 and 12, respectively. Furthermore, CPU11 and 12 diagnose the contents of the ROM14 and 13. As a result, both CPU11 and 12 send four types of results of diagnosis to a common bus 5. The diagnosis result output signals (a)-(d) are supplied to the register 41 of an IO4 via the bus 5. Then a deciding circuit 42 performs decision when it receives a diagnosis end signal G. If a fault is detected, the control outputs of an input/output interface 40 are all set at the safety side (all output relays 43 opened). |
