static void wait(volatile unsigned long dly)
{
    for(; dly > 0; dly--);
}
int main(void)
{
    unsigned long i = 0;
    
    // LED1,LED2,LED3,LED4对应的4根引脚设为输出
    GPBCON = GPB5_out | GPB6_out | GPB7_out | GPB8_out;

    while(1){
        wait(30000);
        GPBDAT = (~(i<<5));         // 根据i的值，点亮LED1,2,3,4
        if(++i == 16)
            i = 0;
    }