nishui_2000

采用PLL可以轻松的使总线达到25M，具体如下：
CLKSEL=0x00; //disable pll;
CLKSEL=0;
CLKSEL_PLLSEL = 0;
PLLCTL_PLLON = 0;
SYNR = 24; //6M晶镇获得25M总线
REFDV = 5;
PLLCTL = 192;
PLLCTL_PLLON = 1;
while(!CRGFLG_LOCK);
CLKSEL_PLLSEL = 1;