12864液晶画点问题

最近在学习12864液晶，写了个画点程序，有点问题。每次画一个点，但是屏幕上确显示很多点，这是什么原因？
/*******************************************
函数名称：LCD_DrawDot
功    能：在任意位置绘制点
参    数：点的位置坐标(uchar x,uchar y)
返回值  ：无
********************************************/
void LCD_DrawDot(uchar x,uchar y)
{
  uchar x_byte,x_bit,y_ping,y_bit;
  uchar tempH,tempL;
  LCD_Write(0x30,0);
  Delayus(72);
  LCD_Write(0x06,0);
  Delayus(72);
  LCD_Write(0x0c,0);
  Delayus(72);
  LCD_Write(0x01,0);
  Delayus(72);
  LCD_Write(0x36,0);//打开扩展指令
  Delayus(72);
  LCD_Write(0x34,0);//关绘图显示
  Delayus(72);
  x_byte = x / 16;
  x_bit = x % 16;
  y_ping = y / 32;
  y_bit = y % 32;   
  LCD_Write(0x80 + y_bit,0);
  LCD_Write(0x80 + x_byte + 8*y_ping,0);
  tempH = LCD_Read();
  tempH = LCD_Read();
  tempL = LCD_Read();
  Delayus(2);
  LCD_Write(0x80 + y_bit,0);
  LCD_Write(0x80 + x_byte + 8*y_ping,0);
  Delayus(1);
  if(x_bit < 8)
  {
    LCD_Write(tempH|(0x01<<(7-x_bit)),1);
    LCD_Write(tempL,1);
  }
  else
  {
    LCD_Write(tempH,1);
    LCD_Write(tempL|(0x01<<(15-x_bit)),1);
  }
  LCD_Write(0x36,0);
  Delayus(72);
  LCD_Write(0x30,0);
  Delayus(72);  
}