#include <msp430x16x.h>
/***************************************************************************************
describe:UART asynchronism  mode  example
***************************************************************************************/
//definition
#define Txdata 0x55

//Init UART asy mode
void Init_Uart()
{
  P3SEL |= 0xC0;                            // P3.6,7 = USART1 option select
  ME2 |= (UTXE1 + URXE1);   // USART1 UART module enable
  U1CTL |= CHAR;  // 8-bit char, UART-mode
  UTCTL1 |= SSEL0;                          // UCLK = ACLK
  U1BR0 = 0x03;   // 9600 baud
  U1BR1 = 0x00;
  U1MCTL = 0x4A;
  U1CTL &= ~SWRST;
  IE2 |= UTXIE1 ;
}

//main
void main()
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  Init_Uart();
  _EINT();
  while(1);
}

//interupt routine
#pragma vector = USART1TX_VECTOR
__interrupt void uart1Tx(void)
{
 TXBUF1 = Txdata; //send
}