MSP430FG4618 UART communication using Timer_A

Hello everyone,

In the code below, the debug cursor is stuck on the line TX_Byte; it doesn't enter the function. Why so?

Krishna.

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#define RXD       0x02                      // RXD on P1.1
#define TXD       0x20                      // TXD on P1.5

//   Conditions for 2400 Baud SW UART, ACLK = 32768

#define Bitime_5  0x06                      // ~ 0.5 bit length + small adjustment
#define Bitime    0x0E                      // 427us bit length ~ 2341 baud

unsigned int RXTXData;
unsigned char BitCnt;

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

//  M. Buccini / L. Westlund
//  Texas Instruments Inc.
//  October 2005
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.40A
//******************************************************************************

//#include  <msp430x20x3.h>
#include <intrinsics.h>
#include <msp430xG46x.h>



void main (void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer
  TACCTL0 = OUT;                              // TXD Idle as Mark
  TACTL = TASSEL_1 + MC_2;                  // ACLK, continuous mode
  P2SEL = TXD + RXD;                        //
  P2DIR = 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/SPo
  //while (TAR != TACCR0);                       // Prevent async capture
  TACCR0 = TAR;                             // Current state of TA counter
  TACCR0 += Bitime;                           // Some time till first bit
  RXTXData |= 0x100;                        // Add mark stop bit to RXTXData
  RXTXData = RXTXData << 1;                 // Add space start bit
  TACCTL0 =  CCIS0 + OUTMOD0 + CCIE;          // TXD = mark = idle
  while ( TACCTL0 & CCIE );                   // Wait for TX completion
}


// Function Readies UART to Receive Character into RXTXData Buffer
void RX_Ready (void)
{
  BitCnt = 0x8;                             // Load Bit counter
  TACCTL0 = SCS + OUTMOD0 + CM1 + CAP + CCIE;   // Sync, Neg Edge, Cap
}

// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)
{
  TACCR0 += Bitime;                           // Add Offset to CCR0

// TX
  if (TACCTL0 & CCIS0)                        // TX on CCI0B?
  {
    if ( BitCnt == 0)
    TACCTL0 &= ~ CCIE;                        // All bits TXed, disable interrupt
    else
    {
      TACCTL0 |=  OUTMOD2;                    // TX Space
      if (RXTXData & 0x01)
      TACCTL0 &= ~ OUTMOD2;                   // TX Mark
      RXTXData = RXTXData >> 1;
      BitCnt --;
    }
  }
// RX
  else
  {
    if( TACCTL0 & CAP )                       // Capture mode = start bit edge
    {
    TACCTL0 &= ~ CAP;                         // Switch from capture to compare mode
    TACCR0 += Bitime_5;
    }
    else
    {
    RXTXData = RXTXData >> 1;
      if (TACCTL0 & SCCI)                     // Get bit waiting in receive latch
      RXTXData |= 0x80;
      BitCnt --;                            // All bits RXed?
      if ( BitCnt == 0)
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
      {
      TACCTL0 &= ~ CCIE;                      // All bits RXed, disable interrupt
      _BIC_SR_IRQ(LPM3_bits);               // Clear LPM3 bits from 0(SR)
      }
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    }
  }
}