这是AD5245的控制字节，我的程序如下：
1.首先是 I2C初始化
void I2CA_Init(void)
{
   // Initialize I2C
         I2caRegs.I2CSAR = 0x58;
   #if (CPU_FRQ_150MHZ)             // Default - For 150MHz SYSCLKOUT
        I2caRegs.I2CPSC.all = 14;   // Prescaler - need 7-12 Mhz on module clk (150/15 = 10MHz)
   #endif
   #if (CPU_FRQ_100MHZ)             // For 100 MHz SYSCLKOUT
     I2caRegs.I2CPSC.all = 9;            // Prescaler - need 7-12 Mhz on module clk (100/10 = 10MHz)
   #endif

   I2caRegs.I2CCLKL = 10;                        // NOTE: must be non zero
   I2caRegs.I2CCLKH = 5;                        // NOTE: must be non zero
   //I2caRegs.I2CIER.all = 0x24;                // Enable SCD & ARDY interrupts
   I2caRegs.I2CIER.all = 0x00;                  // Disable I2CA interrupts
   I2caRegs.I2CMDR.all = 0x0020;          // Take I2C out of reset
                                                                              // Stop I2C when suspended
   //I2caRegs.I2CFFTX.all = 0x6000;        // Enable FIFO mode and TXFIFO
   //I2caRegs.I2CFFRX.all = 0x2040;        // Enable RXFIFO, clear RXFFINT,
   I2caRegs.I2CFFTX.all = 0x0000;          // Disable FIFO mode
   I2caRegs.I2CFFRX.all = 0x0000;          // Disable RXFIFO

   return;
}
2.GPIO初始化省略，但配置正确。
3.写入AD5245控制字节的函数
void write_AD5245(Uint16 slaveAddr, Uint16 Instruction, Uint16 regDat)
{
    // Wait until the STP bit is cleared from any previous master communication.
    // Clearing of this bit by the module is delayed until after the SCD bit is
    // set. If this bit is not checked prior to initiating a new message, the
    // I2C could get confused.
    while(I2caRegs.I2CMDR.bit.STP == 1);

    // Setup slave address
    I2caRegs.I2CSAR = slaveAddr;

    // Check if bus busy
    while(I2caRegs.I2CSTR.bit.BB == 1);

    // Setup number of bytes to send(datLen + 1)
    I2caRegs.I2CCNT = 2;

    // Setup the address to send
    I2caRegs.I2CDXR = Instruction;

    // Send start as master transmitter
    I2caRegs.I2CMDR.all = 0x6E20;

    // Setup data to send
            while(I2caRegs.I2CSTR.bit.XRDY == 0);卡在这里不动
            I2caRegs.I2CDXR = regDat;
    DELAY_US(100);
}

4.调用函数
write_AD5245(0x58, 0x00, GAIN_B_2);
因为AD5245的AD0引脚接地，所以AD5245的地址为0x58。
不知道什么原因，希望大神指点，谢谢！
此帖出自小平头技术问答