我的程序是:

void main(void) {
  /* put your own code here */
  //EnableInterrupts;
  byte test ;
   
  DDRB = 0xff; // PTB as output 
  DDRA = 0x00;  //PTB as input
  
  cDelay(1000);  //延时
  cDelay(1000);  //延时  
  for(;;){
   test = PORTA;  // read can address //   
    if((test & 0x01)==0x01){
      PORTB_BIT4 = 1;       
    }else{
      PORTB_BIT4 = 0;
    }
  } 

}