| 摘要 |
PURPOSE:To prevent data from misrecognition by providing a rewriting monitoring bit in an information word and deciding the information word as a normal one from the processing result of the bit over plural words. CONSTITUTION:A data repeating device 1 transfers data transmitting from a cyclic transmission device TC to a DMA controller 4 together with data updated by regarding the rewriting monitoring bit JA as ''0'' when the data from the TC is normal. When the rewriting monitoring bit JA in the data is ''0'', the rewriting monitoring bit JA ''0'' and the data are stored in a memory 6 so as to attain DMA. A CPU5 scans the data at a period shorter than a TC transmission cycle to check the rewriting monitoring bit JA. When the JA is set up to ''1'', the JA is ignored or invalidated, and in case of ''0'', the data are processed and then the JA is set up to ''1''. After processing the JA over plural words, the CPU5 regards the data as valid one first and then processes the JA. |
