| 摘要 |
PURPOSE:To improve the fetching reliability of an external event state to attain the simultaneous input of the external even state data sent after duplexing with a single computer and selecting a normal transmission route. CONSTITUTION:The state of an external event 5 is sent to DMA devices 31 and 32 via duplex transmission routes 41 and 42. The devices 31 and 32 write double the event 5 to the external event areas 211 and 221 of a shared memory 2. Then the abnormality of both routes 41 and 42 are checked and the result of this check is written to the transmission route state areas 212 and 222. The transmission route monitor processors 112 and 122 in electronic computers 11 and 12 read the areas 212 and 222 of the memory 2 and produce the transmission route states 113 and 123. Then the external event state fetching processors 111 and 121 fetch the normal external event states via the normal one of both transmission routes and the normal DMA device.
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