通常一个指令接收到反向电流指令时，本指令不执行，并且将反向电流传向回路中的下一个指令。然而，定时器或计数器等指令受到反向电流时也会执行，并且向后传播反向电流。一旦一个回路执行完以后，不管输出正向还是反向电流，电流都回传给下一-回路。
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