把下面程序拷贝到头文件中,就可以在C中调用此函数了.

#ifndef __EDGE_H__

#define __EDGE_H__

/*****************************************************************************************/

/* EDGEPOS return 1 at positive transition of signal, in all other cases 0 is returned */

/*****************************************************************************************/

#define EDGEPOS(variable,__buffer) \

({plcbit result; \

if (variable && !__buffer) \

{ \

result=1; \

} \

else \

{ \

result=0; \

} \

__buffer=variable; \

result; \

})

/*****************************************************************************************/

/* EDGENEG return 1 at negative transition of signal, in all other cases 0 is returned */

/*****************************************************************************************/

#define EDGENEG(variable,__buffer) \

({plcbit result; \

if (!variable && __buffer) \

{ \

result=1; \

} \

else \

{ \

result=0; \

} \

__buffer=variable; \

result; \

})

/**************************************************************************************************/

/* EDGE return 1 at positive and negative transition of signal, in all other cases 0 is returned */

/**************************************************************************************************/

#define EDGE(variable,__buffer) \

({plcbit result; \

if (variable != __buffer) \

{ \

result=1; \

} \

else \

{ \

result=0; \

} \

__buffer=variable; \

result; \

})

#endif /*__EDGE_H__*/