stm32f103 spi communication with ad7730 random wrong number

I am communicating with ad7730 (24bit adc) using atm32f103ZCT6. I try to read one of the registers of the adc but each time I receive a random wrong figure. The strange thing is that while debugging using serial wire (STLINK) everything is perfect and I receive correct number from ad7730. But when I run the board out of the power source I receive wrong data. Any help is appreciated in advance