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unsigned char Key_Scan(void)
{
    unsigned char Scan_Code = 0, Read_Code = 0, Key_Value = 0;
   unsigned char Key_Temp = 0;
   DDRC   |= 0x0f;
   PORTC  &= 0xf0; // Row output Low
   DDRD  |= 0xf8; 
   PORTD  |= 0xf8;   // Column output High  
   DDRD  &= 0x07;
   Key_Temp = PIND & 0xf8;
   if( Key_Temp != 0xf8 )
   {      
    Delay_Ms(10);
    if( Key_Temp != 0xf8 )
    {
     Scan_Code = 0xfe; 
     while( Scan_Code != 0xff )
     {     
     PORTC = ( Scan_Code & 0x0f );
     Key_Temp = PIND & 0xf8; // 再读具体行
     if( Key_Temp != 0xf8 )
     {
      Read_Code = (Key_Temp & 0xf8) | 0x07;
      Key_Value |= ( ~Scan_Code ) + ( ~Read_Code );
     }
     Scan_Code = ( Scan_Code << 1 ) | 0x01;
     }
    }
   }
  PORTC  &= 0x0f;
  return ( Key_Value );      
}