xs128键盘程序

#include <hidef.h>      /* common defines and macros */
#include "derivative.h"      /* derivative-specific definitions */


int keyscan()
{
  unsigned char key;
  byte temp=0;
  DDRB=0x00;
  DDRT=0x0f;
while(PTT==0x0e){
  if(PORTB&0xf0!=0xf0)
  {
    temp=PORTB&0xf0;
    switch(temp)
    {
       case 0xe0: key=1;break;
       case 0xd0: key=2;break;
       case 0xb0: key=3;break;
       case 0x70: key=4;break;
     }
    return key;
  }
}
while(PTT==0x0d)
{
   if(PORTB&0xf0!=0xf0)
  {
    temp=PORTB&0xf0;
    switch(temp)