TMS320F280049: SPIB SIMO吴信号输出

MCU SPI能输出时钟信号，SOMI能接收外部输入信号，但是SIMO无输出信号，一直为0

IO映射：

RESET ：GPIO56

DRDY   ：GPIO27

SCLK    ：GPIO26

SOMI    ：GPIO31

SIMO    ：GPIO30

SPI从设备为ads131m06，不管mcu发出什么数据，SIMO上捕获到的数据总是0.

将GPIO30配置为普通IO，可以控制其高低电平。

请帮忙看看是哪里出了问题

初始化SPI代码：

void SPI_Initialize(void)
{
    SpibRegs.SPICCR.bit.SPISWRESET = 0;     //spi reset to configuration mode
    SpibRegs.SPICCR.bit.CLKPOLARITY = 0;    //DOut on falling Edge,Din on rising Edge
    SpibRegs.SPICCR.bit.SPICHAR = (8-1);   //16-bit word
    SpibRegs.SPICCR.bit.SPILBK = 0;         //loopback disabled

    SpibRegs.SPICTL.bit.MASTER_SLAVE = 1;   //Master
    SpibRegs.SPICTL.bit.TALK = 1;           //Transmit Enable
    SpibRegs.SPICTL.bit.CLK_PHASE = 0;      //normal clocking scheme,no delaying
    SpibRegs.SPICTL.bit.SPIINTENA = 0;      //Interrupt Disable

    SpibRegs.SPIBRR.bit.SPI_BIT_RATE = SPI_BRR; //500kbps

    SpibRegs.SPIPRI.bit.FREE = 1;           //Halting on a breakpoint will not halt the SPI

    DELAY_US(10);

    //b15,SPIRST    =1,resume FIFO to transmit or receive
    //b14,SPIFFENA  =1,enable FIFO
    //b13,TXFIFO    =1,release TX FIFO from reset
    //b6,TXFFINTCLR =1,clear SPIFFTX[TXFFINT] flag
    //b4~b0,TXFFIL  =4,generate TX FIFO interrupt when there are less than 4 words in TX buffer
    SpibRegs.SPIFFTX.all = 0xE040;
    //b13,RXFIFORESET=1,re-enable RXFIFO
    //b6,RXFFINTCLR =1,clear SPIFFRX[RXFFINT] flag
    //b4-b0,RXFFIL  = F,generate RX FIFO intterupt when there are more than 15 words in RX buffer
    SpibRegs.SPIFFRX.all = 0x204F;
    //no delay between every transfer from FIFO transmit buffer to transmit shift register
    SpibRegs.SPIFFCT.all = 0x0;    

    SpibRegs.SPICCR.bit.SPISWRESET = 1;     //Release the SPI from reset

    SPI_InitGpio();
}
//
// InitSpiGpio - Initialize SPIA GPIOs
//
void SPI_InitGpio()
{
    EALLOW;
    GpioCtrlRegs.GPAPUD.bit.GPIO30 = 0; // Enable pull-up  (SPISIMO)
    GpioCtrlRegs.GPAPUD.bit.GPIO31 = 0; // Enable pull-up  (SPISOMI)
    GpioCtrlRegs.GPAPUD.bit.GPIO26 = 0; // Enable pull-up  (SPICLK)
    GpioCtrlRegs.GPAPUD.bit.GPIO27 = 0; // Enable pull-up  (SPISTE)

    GpioCtrlRegs.GPAQSEL2.bit.GPIO30 = 3; // Asynch input  (SPISIMO)
    GpioCtrlRegs.GPAQSEL2.bit.GPIO31 = 3; // Asynch input  (SPISOMI)
    GpioCtrlRegs.GPAQSEL2.bit.GPIO26 = 3; // Asynch input  (SPICLK)
    GpioCtrlRegs.GPAQSEL2.bit.GPIO27 = 3; // Asynch input  (SPISTE)

    GpioCtrlRegs.GPAGMUX2.bit.GPIO30 = 0; //0x3
    GpioCtrlRegs.GPAMUX2.bit.GPIO30  = 3; //SPIB_SIMO 
    GpioCtrlRegs.GPAGMUX2.bit.GPIO31 = 0; //0x3
    GpioCtrlRegs.GPAMUX2.bit.GPIO31  = 3; //SPIB_SOMI 
    GpioCtrlRegs.GPAGMUX2.bit.GPIO26 = 1; //0x6
    GpioCtrlRegs.GPAMUX2.bit.GPIO26  = 2; //SPIB_CLK 

    GpioCtrlRegs.GPAGMUX2.bit.GPIO27 = 0; //
    GpioCtrlRegs.GPAMUX2.bit.GPIO27  = 0; //
    GpioCtrlRegs.GPADIR.bit.GPIO27   = 0; // Input
    GpioCtrlRegs.GPAPUD.bit.GPIO27   = 0; // Enable pull-up /DRDY
    GpioCtrlRegs.GPACTRL.bit.QUALPRD3= 0x3;//6 SYSCLK cycles

	GpioCtrlRegs.GPBGMUX2.bit.GPIO56 = 0;
	GpioCtrlRegs.GPBMUX2.bit.GPIO56  = 0;
    GpioCtrlRegs.GPBPUD.bit.GPIO56 = 0; // Enable pull-up  (SPI /RESET)
    GpioCtrlRegs.GPBDIR.bit.GPIO56 = 1; // Output
    
    GpioDataRegs.GPBSET.bit.GPIO56 = 1; // High
    // GpioDataRegs.GPBCLEAR.bit.GPIO56 = 1; // Low,保持复位状态


    //GpioCtrlRegs.GPAGMUX2.bit.GPIO30 = 0; //0
    //GpioCtrlRegs.GPAMUX2.bit.GPIO30  = 0; //GPIO30
    //GpioCtrlRegs.GPADIR.bit.GPIO30 = 1; // Output

    EDIS;
}