12864显示屏怎么全屏上下滚动，还有左右滚动

#include "lcd12864.h"

void main()
{
unsigned char i;
lcd_init();

lcd_pos(11,0);
lcd_wstring("wjh776a68");
lcd_pos(12,0);
lcd_wstring("参考链接 blog.51");
lcd_pos(13,0);
lcd_wstring("cto.com/rainlee/");
lcd_pos(14,0);
lcd_wstring("1415034 ");
lcd_pos(21,0);
lcd_wstring("cto.com/rainlee/");
lcd_pos(22,0);
lcd_wstring("1415034 ");
lcd_pos(23,0);
lcd_wstring("wjh776a68");
lcd_pos(24,0);
lcd_wstring("参考链接 blog.51");

for(i=0x00;i<0x64;i++)
{
    
    LCD_RS = 0;
    LCD_RW = 0;
    
    
    //lcd_wcmd(0x1f);           //0001 11xx 向右滚屏
    //lcd_wcmd(0x14);           //0001 01xx 向左滚屏
    
    
    lcd_wcmd(0x34);                //进入扩充指令操作 0011 x1xx
    
    lcd_wcmd(0x03);                //设置滚屏 0000 0011
    
    lcd_wcmd(0x40 + i);         //设置纵向滚屏地址
    
    
    lcd_wcmd(0x30);                //返回基本指令操作 0011 x000
    
    lcd_delay(1000);


}
    



while(1);

}
请问一下为什么12864只能半屏滚动如果想要全屏的话代码怎么写