本人小白一只，最近在调试STM32f407通过SPI驱动TMC5160。在调试过程中初始化TMC5160，往SPI写字节使在while (SPI_I2S_GetFlagStatus(SPI3, SPI_I2S_FLAG_TXE) == RESET）处出现死循环。用的是SPI3。请教各位大神这是什么原因？SPI3的配置程序如下：

void SPI3_Init(void)
{  
GPIO_InitTypeDef  GPIO_InitStructure;
SPI_InitTypeDef  SPI_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);           
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);   
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10|GPIO_Pin_11|GPIO_Pin_12; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;                 
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;                
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;            
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;                  
GPIO_Init(GPIOC, &GPIO_InitStructure);                         
      
SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex; 
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;                   
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;                
SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;                    
SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;                 
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;                       
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
//SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_32;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;                
SPI_InitStructure.SPI_CRCPolynomial = 0;                        
SPI_Init(SPI3, &SPI_InitStructure);                               

SPI_Cmd(SPI3, ENABLE);    

SPI3_ReadWriteByte(0xff); 

} 
读写单个字节如下：
u8 SPI1_ReadWriteByte(u8 writeData)
{    
   u8 waitnum=0;
  while (SPI_I2S_GetFlagStatus(SPI3, SPI_I2S_FLAG_TXE) == RESET){}   
      {  
    waitnum++;  
    if(waitnum>200)return 0;  
}
SPI_I2S_SendData(SPI3, writeData);  

  while (SPI_I2S_GetFlagStatus(SPI3, SPI_I2S_FLAG_RXNE) == RESET){} 
        {  
    waitnum++;  
    if(waitnum>200)return 0;  
}
return SPI_I2S_ReceiveData(SPI3);     
}