问题
单项选择题
西门子S7系列PLC处在STOP状态，所有指示灯在闪烁的故障原因是（）。
A.有相当数量的卡件掉电
B.有通讯卡件的接口松动
C.CPU运行时间长期被硬件中断占用
D.超出CPU中设定的Watch Dog时间
答案
参考答案：B
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西门子S7系列PLC处在STOP状态，所有指示灯在闪烁的故障原因是（）。
A.有相当数量的卡件掉电
B.有通讯卡件的接口松动
C.CPU运行时间长期被硬件中断占用
D.超出CPU中设定的Watch Dog时间
参考答案：B
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