TMS320C6748: SPI Slave of C6748 not transmitting data

Part Number:TMS320C6748

I use the ti\C6748_StarterWare_1_20_04_01\examples\evmC6748\spi_edma    example.

And the spi_clk is set to 1MHz.

The stareware example is a "SPI_MASTER" example. I use a oscilloscope to monitor the SPI_CLK and SPI_MOSI, and it's alright.

Then I make the only one changes on the code:  "    SPIModeConfigure(SOC_SPI_1_REGS, SPI_SLAVE_MODE);

Nothing else in the example code is changed.

I connect the SPI_CS to GND, and use SIGNAL GENERATOR to generate a 1MHz 0-3.3V square wave to the SPI_CLK.

But when the Slave code is running, nothing was sent out on SPI_MOSI.

Question: Is there anything else that should be modified for the SPI_SLAVE mode? Is there any example code for the SPI_SLAVE mode?

Thank you.