//書本配套代碼參考P229_S1_F44X.C文件
//修改實例如下

//例1 MSP430F149在ACLK = LFXT1 = 32768Hz，MCLK = SMCLK = UCLK0 = XT2 = 8MHz頻率驅動下以115200波特率異步串行通信，采用中斷方式接收并發送收到的數據。P229
//計算波特率分頻因子：8000000Hz/115200~9.1(069h|52h)。
//相關程序如下：
#include <msp430x14x.h>
void main(void)
{
  	unsigned int i;
	WDTCTL = WDTPW + WDTHOLD;	
	P3SEL |= 0x30;                            //P3.4，5用作USART0 TXD/RXD
	P3DIR |= 0x10;  						  //P3.4輸出
	BCSCTL1 &= ~XT2OFF;                       // XT2on
	do
	{
		IFG1 &= ~OFIFG;						// Clear OSCFault flag
		for (i = 0xFF; i > 0; i--);			// Time for flag to set
	}
	while ((IFG1 & OFIFG));                   // OSCFault flag still set?	
	BCSCTL2 = 0x88 ;                 		// MCLK = SMCLK = XT2 (safe)
	
	ME1 |= UTXE0 + URXE0;	// Enable USART0 TXD/RXD
	UCTL0 = CHAR;		// 8-bit character
	UTCTL0 = SSEL1;		// UCLK = SMCLK
	UBR00 = 0X41;		// 8Mhz/112500 = 104.167
	UBR10 = 0X3;		//
	UMCTL0 = 0X49;		// modulation
	
	UCTL0 &= ~SWRST;      	// Initialize USART state machine
	IE1 |= URXIE0;		// Enable USART0 RX interrupt


	_EINT();								  // 允許中斷
	for(;;)
	{
		_BIS_SR(CPUOFF);  //進入LPM0
		_NOP();	
	}
}
#pragma vector = UART0RX_VECTOR
__interrupt void usart0_rx (void)
{
	while ((IFG1 & UTXIFG0) == 0);  //USART0接收緩存有數據嗎？
	TXBUF0 = RXBUF0;  //讀出接收到數據，再轉發回去
}
/*
//同理，當ACLK = UCLK0 = LFXT1 = 32768Hz，MCLK = SMCLK = DCO~800k，波特率為2400時，實現上述同樣功能，只需要改變相關波特率寄存器設置：
UBR00 = 0x0D;  //32k/2400=13.65
UBR10 = 0x00;  
UMCTL0 = 0x6B;  //波特率調整

//當ACLK=LFXT1=32768Hz，MCLK=SMCLK=UCLK0=DCOCLK=1048576Hz，波特率為9600時，相關波特率寄存器設置：
UBR00 = 0x6D;  //1048576Hz/9600~109.23
UBR10 = 0x00;  //1MHz 9600
UMCTL0 = 0x81;  //波特率調整
*/