plc 梯形图转AVR PIC 单片机程序

代码说明：

> CONTACT, NORMALLY OPEN        Xname           Rname          Yname                              ----] [----     ----] [----    ----] [----     If the signal going into the instruction is false, then the output     signal is false. If the signal going into the instruction is true,     then the output signal is true if and only if the given input pin,     output pin, or internal relay is true, else it is false. This     instruction can examine the state of an input pin, an output pin,     or an internal relay. >