这个单片机可以超频到80M，仍然比较稳定，具体函数我已经在自己设计的开发板上多次使用，直接调用即可：

void SetBusCLK_40M(void)
{
CLKSEL=0X00; //disengage PLL to system
PLLCTL_PLLON=1; //turn on PLL
SYNR=9;
REFDV=3; //pllclock=2*osc*(1+SYNR)/(1+REFDV)=80MHz;
_asm(nop); //BUS CLOCK=40M
_asm(nop);
while(!(CRGFLG_LOCK==1)); //when pll is steady ,then use it;
CLKSEL_PLLSEL =1; //engage PLL to system;
}

void SetBusCLK_80M(void)
{
CLKSEL=0X00; //disengage PLL to system
PLLCTL_PLLON=1; //turn on PLL
SYNR=9;
REFDV=1; //pllclock=2*osc*(1+SYNR)/(1+REFDV)=160MHz;
_asm(nop); //BUS CLOCK=80M
_asm(nop);
while(!(CRGFLG_LOCK==1)); //when pll is steady ,then use it;
CLKSEL_PLLSEL =1; //engage PLL to system;
}