Send and Receiving Data simultaneously using SPI core as Slave in NIOS II processor.

I am using SPI core in NIOS II processor to communicate with a DSP Board (which can be only configured as SPI master). I have configured the SPI core as Slave and can receive data successfully. As SPI is a fully duplex communication protocol, i want to send data while being configured as Slave.

I am not able to figure out what function should I use to achieve this. Could someone help me?

Thanks alot in advance!