| 摘要 |
PURPOSE:To secure the validity of data and to detect a fault with a data transmission system by providing a data replacement flag to specify that the data given from an input station is replaced. CONSTITUTION:The process input stations 4a and 4b collect data in a fixed cycle and send them to a transmission line 3 after turning them into clocks. Then the stations of the CPU1a and 1b store at a time those data in their own data memories 2a and 2b respectively and also set the data replacement bits 5a and 5b at '1'. The memories 2a and 2b are replaced in the reception cycles given from stations 4a and 4b. It is possible to know the immediately preceding process input data by reading the memories 2a and 2b in a cycle longer than the data replacement cycle.
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