不懂UART怎么通信啊，懂的帮忙

学430 lanchpad板上的TimerA模拟uart通信，总是不成功，下面是TI的演示程序，只做了简单修改，可用串口调试软件观察还是没数据，不知道那个地方有问题

#include  <msp430g2231.h>

#define RXD       BIT2                      // RXD on P1.2
#define TXD       BIT1                      // TXD on P1.1
#define Bitime_5  0x05*4                     
#define Bitime    13*4 
unsigned int RXTXData=10;
unsigned char BitCnt;

void TX_Byte (void);
void RX_Ready (void);
void InitializeClocks(void);

void main (void)
{
  WDTCTL = WDTPW + WDTHOLD;                
  InitializeClocks();
  CCTL0 = OUT;                              // TXD Idle as Mark
  TACTL = TASSEL_2 + MC_2+ID_3;             // ACLK, continuous mode
  P1SEL = TXD + RXD;                        //
  P1DIR = TXD;                              //

// Mainloop
  for (;;)
  {
    RX_Ready();                         // UART ready to RX one Byte
    _BIS_SR(LPM3_bits + GIE);           // Enter LPM3 w/ interr until char RXed
    TX_Byte();                          // TX Back RXed Byte Received
  }
}

// Function Transmits Character from RXTXData Buffer
void TX_Byte (void)
{
  BitCnt = 0xA;                             // Load Bit counter, 8data + ST/SP
  while (CCR0 != TAR)                       // Prevent async capture
    CCR0 = TAR;                             // Current state of TA counter
  CCR0 += Bitime;                           // Some time till first bit
  RXTXData |= 0x100;                        // Add mark stop bit to RXTXData
  RXTXData = RXTXData << 1;                 // Add space start bit
  CCTL0 =  CCIS0 + OUTMOD0 + CCIE;          // TXD = mark = idle
  while ( CCTL0 & CCIE );                   // Wait for TX completion
}

// Function Readies UART to Receive Character into RXTXData Buffer
void RX_Ready (void)
{
  BitCnt = 0x8;                             // Load Bit counter
  CCTL0 = SCS + OUTMOD0 + CM1 + CAP + CCIE; // Sync, Neg Edge, Cap
}

// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)
{
  CCR0 += Bitime;                           // Add Offset to CCR0

// TX
  if (CCTL0 & CCIS0)                        // TX on CCI0B?
  {
    if ( BitCnt == 0)
    CCTL0 &= ~ CCIE;                        // All bits TXed, disable interrupt
    else
    {
      CCTL0 |=  OUTMOD2;                    // TX Space
      if (RXTXData & 0x01)
      CCTL0 &= ~ OUTMOD2;                   // TX Mark
      RXTXData = RXTXData >> 1;
      BitCnt --;
    }
  }
// RX
  else
  {
    if( CCTL0 & CAP )                       // Capture mode = start bit edge
    {
    CCTL0 &= ~ CAP;                         // Switch from capture to compare mode
    CCR0 += Bitime_5;
    }
    else
    {
    RXTXData = RXTXData >> 1;
      if (CCTL0 & SCCI)                     // Get bit waiting in receive latch
      RXTXData |= 0x80;
      BitCnt --;                            // All bits RXed?
      if ( BitCnt == 0)
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
      {
      CCTL0 &= ~ CCIE;                      // All bits RXed, disable interrupt
      _BIC_SR_IRQ(LPM3_bits);               // Clear LPM3 bits from 0(SR)
      }
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    }
  }
}
void InitializeClocks()
{
  BCSCTL1 = CALBC1_1MHZ;                   
  DCOCTL = CALDCO_1MHZ;
  BCSCTL2 &= ~(DIVS_3);                    
}