Unknown function at some address

Hi Everyone

I was trying to get the BLE Uart working with the nrf52840. 

Everything works fine, all files are compiling and running, but when i debug the code using segger embedded studio.

It reaches the function gap_params_init(); ,but it says unknown function at  0x00000978 .

And then it does nothing.

Do anyone here have any idea about why is it happening and what is the solution to this?

I am using the same code as given in sdk15.0 inside ble_app_uart.

When i run the example code, it works fine but not when i run my own code.