SSI Module Not Responsive

 Hi,

We just added a new peripheral to our board that requires SSI communication, with the micro (tm4c1231h6pz) being master.  I've followed the spi_master.c example, but can't get the SSI0 module to be responsive.  After configuration, I see the select line (FFS) high, but when I monitor with a scope CLK, FFS, and TX during SSIDataPut, there are no changes on any of those lines (FFS stays high, CLK and TX show no output).  Am I missing some step in the initialization?  My code is below.  The "while(SSIBusy(SSI0_BASE))" statement passes, as if the data actually went out.

I tried initializing SSI1 as a sanity check and got the same results.

Thanks,

Cindy

     uint32_t pui32DataTx[3];

    ROM_SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI0);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

    GPIOPinConfigure(GPIO_PA2_SSI0CLK);

    GPIOPinConfigure(GPIO_PA3_SSI0FSS);

    GPIOPinConfigure(GPIO_PA4_SSI0RX);

    GPIOPinConfigure(GPIO_PA5_SSI0TX);

    GPIOPinTypeSSI(GPIO_PORTA_BASE, GPIO_PIN_5 | GPIO_PIN_4 | GPIO_PIN_3 | GPIO_PIN_2);

    SSIConfigSetExpClk(SSI0_BASE, ROM_SysCtlClockGet(), SSI_FRF_MOTO_MODE_0,

                       SSI_MODE_MASTER, 1000000, 8);

    SSIEnable(SSI0_BASE);

    pui32DataTx[0] = 's';

    SSIDataPut(SSI0_BASE, pui32DataTx[0]);

    while(SSIBusy(SSI0_BASE))

    {

    }