| 摘要 |
This invention enables the number of required ports on a CPU to be reduced, in a switching circuit detecting any exchanged contact point out of plural points having more than three points. In a switching circuit enabling one line to connect to any one of plural lines having more than 3 lines, one line is connected to an input port of the CPU, and one of the plural lines to be switched is connected to a referencing voltage source, and another line of said plural lines to be switched is grounded, and the remaining lines of the plural lines to be switched are connected to output ports of the CPU, and furthermore, the output ports are designed to generate referencing voltages having specified generating timings differing from the timing of data sampling signals transferred to the input port.
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