| 摘要 |
PROBLEM TO BE SOLVED: To provide a duplex system of an inner board in a programmable controller having two CPU units on which the inner board is mounted. SOLUTION: In the system, as for two inner boards, the one mounted on an active CPU unit is defined as active and the one mounted on a standby CPU unit is defined as standby. Each inner board asynchronously executes arithmetic operations with each CPU unit (ST12, ST32), their arithmetic operation execution results are not written in a memory during execution of the arithmetic operations and transferred from the inner board to the CPU units during synchronization processing with the CPU units (ST14, ST34). The CPU units compare the transferred arithmetic operation results, when they do not coincide with each other, the arithmetic operation is continued to the delayed one, permit writing at a state that progress degree is matched and thus, write the arithmetic operation results in the memory. COPYRIGHT: (C)2004,JPO
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