请问高手：
typedef struct
{
   volatile struct EPWM_REGS *EPwmRegHandle;
   Uint16 EPwm_CMPA_Direction;
   Uint16 EPwm_CMPB_Direction;
   Uint16 EPwmTimerIntCount;
   Uint16 EPwmMaxCMPA;
   Uint16 EPwmMinCMPA;
   Uint16 EPwmMaxCMPB;
   Uint16 EPwmMinCMPB;   
}EPWM_INFO;
// Global variables used in this example
EPWM_INFO epwm4_info;
void update_compare(EPWM_INFO*);

想在其他的.c文件使用void update_compare(EPWM_INFO*)函数该怎么调用，直接调用的话显示undefined。
请赐教：