使用MSP430的IIC模块，无时钟信号问题
使用msp430F5529的IIC模块 SCL无时钟输出，这个问题可能出现在什么地方？？
使用msp430F5529的IIC模块，控制一个数字电阻器DS1803，将P3.0（UCB0IICSDA）和P3.1（UCB0IICSCL）与ds1803的对应管脚连接，同时通过上拉电阻连接DVCC（3.3V），按照示例程序，修改从机地址和发送内容，完全没响应。
用示波器查看，3.1没有时钟输出，只有开始时候跳变到底，这是个什么情况？
有大神能帮帮忙吗，调了3天了，查到了一些问题，但是无助于结果啊？
程序如下：
#include "msp430x552x.h"
unsigned char *PTxData; // Pointer to TX data
unsigned char TXByteCtr;
const unsigned char TxData[] = // Table of data to transmit
{ 0xA9,0xFB }; // 这里的发送内容做了改动
void main(void)
{
unsigned int i;
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P3SEL |= 0x03; // Assign I2C pins to USCI_B0
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset
UCB0BR0 = 12; // fSCL = SMCLK/12 = ~100kHz
UCB0BR1 = 0;
UCB0I2CSA = 0x29; // Slave Address is 048h
//从地址由示例程序更改。由此确定start后的首字节为0x53，01010011,1-7位为从地址，0位为R/W位。
UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
UCB0IE |= UCTXIE + UCNACKIE; // Enable TX interrupt
for(i=0;i<10;i++); // Delay required between transaction
PTxData = (unsigned char *)TxData; // TX array start address
// Place breakpoint here to see each
// transmit operation.
TXByteCtr = sizeof TxData; // Load TX byte counter
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent
UCB0CTL1 |= UCTR + UCTXSTT; // I2C TX, start condition
__bis_SR_register(LPM0_bits + GIE); // Enter LPM0, enable interrupts
__no_operation(); // Remain in LPM0 until all data
}
//------------------------------------------
// The USCIAB0TX_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count. Also, TXData
// points to the next byte to transmit.
//------------------------------------------
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
{
switch(__even_in_range(UCB0IV,12))
{
case 0: break; // Vector 0: No interrupts
case 2: break; // Vector 2: ALIFG
case 4:
__no_operation();
break; // Vector 4: NACKIFG
case 6: break; // Vector 6: STTIFG
case 8: break; // Vector 8: STPIFG
case 10: break; // Vector 10: RXIFG
case 12: // Vector 12: TXIFG
if (TXByteCtr) // Check TX byte counter
{
UCB0TXBUF = *PTxData++; // Load TX buffer
TXByteCtr--; // Decrement TX byte counter
}
else
{
UCB0CTL1 |= UCTXSTP; // I2C stop condition
UCB0IFG &= ~UCTXIFG; // Clear USCI_B0 TX int flag
__bic_SR_register_on_exit(LPM0_bits); // Exit LPM0
}
default: break;
}
}
