DCORSEL的设置好像很宽泛,比如下面的代码
查datasheet发现在DCOx和MODx的设置为0000时,DCO的范围并不能到4.9Mhz
__bis_SR_register(SCG0); // Disable the FLL control loop
UCSCTL0 = 0x0000; // Set lowest possible DCOx, MODx
UCSCTL1 = DCORSEL_3; // Set RSELx for DCO = 4.9 MHz
UCSCTL2 = FLLD_1 + 74; // Set DCO Multiplier for 2.45MHz