使用msp430f5529的定时器A开捕获模式，一直进不了中断

使用msp430f5529LP,用定时器A开捕获模式，捕获方波，P1.2口输入，幅值2.8V，一直进不了中断

#include<msp430f5529.h>
#define uchar unsigned char
#define uint unsigned int

void TIMEA_INIT()
{
TA0CCTL1|=CM_3+CCIS_1+CCIE+CAP+SCS;

TA0CTL=TASSEL_1+TACLR+MC_1; 
}

void main()
{
WDTCTL = WDTPW + WDTHOLD; //关闭看门狗

P1DIR = 0XFF;P1OUT = 0xff;

P1SEL|=BIT2;

 TIMEA_INIT();

 __bis_SR_register(LPM0_bits+GIE);  

}

#pragma vector=TIMER0_A0_VECTOR //定时器冲断
__interrupt void TIMER0_A0_ISR(void)
{

P1OUT&=~BIT0;
}