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STM32f4 SPI spurious Interrupt problem

Question asked by p.jagdish on Aug 27, 2014
Latest reply on Aug 27, 2014 by Clive One
Kindly help me resolve the STM32F4 SPI interrupt problem.
I am trying to connect two stm32f4 boards, one of it is stm32f439 evaluation board and other one is stm32f407 based my development board. I am testing interrupt based SPI communication example. I am using SPI1 peripheral for both boards. I have configured STM32F439 eval board as Master and my STM32F407 based dev't board as slave. 
Have enabled Rx interrupt on slave board. I have grounded SPI slave cs pin and have configured slave with SPI_NSS_Soft setting.

I am expecting that when i start transferring data from master board, slave board should invoke SPI rx interrupt ISR.
But here what i observed is that as soon as my slave board boots up it gets SPI receive interrupt. It doesn't wait for master to send data. I tried this even without connecting Master card signals to Slave card.
I am unable to understand what triggers the SPI interrupt. Is it a setting problem or hardware problem
I understand that when rx data register is not empty, Rx interrupt will occur

Kindly help.