加上这几句试试:
// Disable VUSB LDO and SLDO
USBKEYPID = 0x9628; // set USB KEYandPID to 0x9628
// access to USB config registers enabled
USBPWRCTL &= ~(SLDOEN+VUSBEN); // Disable the VUSB LDO and the SLDO
USBKEYPID = 0x9600; // access to USB config registers disabled
// Disable SVS
PMMCTL0_H = PMMPW_H; // PMM Password
SVSMHCTL &= ~(SVMHE+SVSHE); // Disable High side SVS
SVSMLCTL &= ~(SVMLE+SVSLE); // Disable Low side SVS