MSP5438A接25M晶振,33pf电容,晶振波形不稳定,有时候晶振停振,有时候程序运行一半就停了,但是P11口的特殊功能引脚还在输出波形,
25M是接多大的电容合适?我的波形接近正弦,但是偶尔出现几条重叠的波形,相位不同,
void MCU_Init(void) {
WDTCTL = WDTPW + WDTHOLD; P11DIR = BIT1+BIT2+ BIT0; // P11.1-2 to output direction
P11SEL |= BIT1+BIT2 + BIT0; // P11.1-2 to output SMCLK,MCLK
P5SEL |= 0x0C; // Port select XT2
UCSCTL6 &= ~XT2OFF; // Enable XT2
UCSCTL6 |= 0xc000; //crease to 18M
UCSCTL3 |= SELREF_2; // FLLref = REFO
UCSCTL4 |= SELA_2 + SELM_5; // ACLK=REFO,SMCLK=DCO,MCLK=DCO
do {
UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + XT1HFOFFG + DCOFFG); // Clear XT2,XT1,DCO fault flags
SFRIFG1 &= ~OFIFG; // Clear fault flags
}while (SFRIFG1&OFIFG); // Test oscillator fault flag // expected frequency
UCSCTL4 |= SELS_5 + SELM_5; //UCSCTL5 |=DIVM__8; // SMCLK=MCLK=XT2
}
晶振换了几个,仿真时不能正常运行,有时候按好几次复位后能正常运行