MSP430F1232串口通信问题

Hi，Everyone：

我有个问题，在使用MSP430F1232的时候遇到串口通信失败，无法接收到数据的情况，板子参考TI官方的Launchpad。

代码如下：

//  MSP-FET430P120 Demo - USART0, UART 9600 Echo ISR, 32kHz ACLK + DCO
//
//  Description: Echo a received character, USART0 RX ISR at high-speed using
//  32kHz XTAL and DCO. Normal operation in LMP0, DCO continuously stabilized,
//  interrupt driven using CCR2. DCO used for UART baud generation. On a valid
//  RX character, character is echoed back.
//  Baud rate divider with 2MHz = 2MHz/9600 ~ 208 (00D0h)
//  ACLK = LFXT1/8 = 32768/8, MCLK = SMCLK = UCLK0 = DCOCLK  ~2MHz
//  //* An external 32kHz watch crystal on XIN XOUT is required for ACLK *//
//               MSP430F123(2)
//             -----------------
//         /|\|              XIN|-
//          | |                 | 32768Hz
//          --|RST          XOUT|-
//            |                 |
//            |             P3.4|------------>
//            |                 | 9600 - 8N1
//            |             P3.5|<------------


#include <msp430.h>
#define DELTA 488                           // target DCO = DELTA*(4096) ~2MHz

void delayms(int t)
{
    int i;
    while(t--)
      for(i=150;i>0;i--);     //delay ms
}

unsigned int Compare, Oldcapture;

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1SEL=0;                                  // SET P1 AS IO
  P1DIR=0xFF;                               //SET P1 DIR OUT
  P1OUT=0xFF;                               //P1 OUT VALUE
  
  P3SEL |= 0x30;                            // P3.4,5 = USART0 TXD/RXD
  BCSCTL1 |= DIVA_3;                        // ACLK = LFXT1CLK/8
  ME2 |= UTXE0 + URXE0;                     // Enabled USART0 TXD/RXD
  UCTL0 |= CHAR;                            // 8-bit character
  UTCTL0 |= SSEL1;                          // UCLK = SMCLK
  UBR00 = 0xD0;                             // 2MHz 9600
  UBR10 = 0x00;                             //
  UMCTL0 = 0x00;                            // no modulation
  UCTL0 &= ~SWRST;                          // Initalize USART state machine
  IE2 |= URXIE0;                            // Enabled USART0 RX interrupt
  CCTL2 = CM_1 + CCIS_1 + CAP + CCIE;       // CAP, ACLK, interrupt
  TACTL = TASSEL_2 + MC_2 + TACLR;          // SMCLK, cont-mode, clear

  __bis_SR_register(LPM0_bits + GIE);       // Enter LPM0 w/ interrupt
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USART0RX_VECTOR
__interrupt void usart0_rx (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USART0RX_VECTOR))) usart0_rx (void)
#else
#error Compiler not supported!
#endif
{
  while (!(IFG2 & UTXIFG0));                // USART0 TX buffer ready?
  TXBUF0 = RXBUF0;                          // RXBUF0 to TXBUF0
  
   //while receive the data, led blink and resend data to tx.
  P1OUT=1;
  delayms(50);                              //delay
     
  P1OUT=0;
  delayms(50);                              //delay
}


// Timer_A3 Interrupt Vector (TAIV) handler
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(TIMERA1_VECTOR))) Timer_A (void)
#else
#error Compiler not supported!
#endif
{
  switch( TAIV )
  {
    case  2: break;                         // CCR1 not used
    case  4:
    {
    Compare = CCR2;                         // Get current captured SMCLK
    Compare = Compare - Oldcapture;         // SMCLK difference
    Oldcapture = CCR2;                      // Save current captured SMCLK
    if (DELTA < Compare)
      {
        DCOCTL--;
        if (DCOCTL == 0xFF)                 // DCO is too fast, slow it down
        {
          if (!(BCSCTL1 == (XT2OFF + DIVA_3)))
          BCSCTL1--;                        // Did DCO role under?, Sel lower RSEL
        }
      }
    else
      {
        DCOCTL++;                           // DCO is too slow, speed it down
        if (DCOCTL == 0x00)
        {
          if (!(BCSCTL1 == (XT2OFF + DIVA_3 + 0x07)))
          BCSCTL1++;                        // Did DCO role over? Sel higher RSEL
        }
      }
    }
  case 10: break;                           // not used
  }
}

但串口依旧无法收发数据，通过示波器测得串口通信工具发送波形如下，请TI专家帮忙分析一下，谢谢！