synchronization across multiple AD7134 devices

We are using two AD7134 for our acquisition system. To synchronize multiple devices the AD7134 datasheet mentions " SPI to set the DIG_IF_RESET bit to reset the digital interface before the data capture This DIG_IF_RESET command must be given to all the slaves simultaneously using one single SPI write command."

We have set both the AD7134 devices in slave mode and they have independent oscillator for sysclk(MCLK). We program the registers of each device (setting soft reset/frame sel/data mode/other necessary register) independently and then we set dig_if_reset in both the adc by using a common cs signal.  But we are unable to achieve synchronization between the ADC devices. The synchronization is varying for each execution.

Are we missing any sequence in the SPI programming. To cross verify we probed the spi signals of ad7134 evaluation board in cro. There we noticed that following registers are programmed.

register Device 1 Val Device 2 Val
0x02 0xF3 0xF3
0x10 0x02 0x02
0x11 0x50 0x50
0x12 0x02 0x02
0x1F 0x00 0x00
0x1e 0xaa 0xaa
0x18 0x00 not programmed
0x17 0x5D not programmed
0x16 0xC0 not programmed
0x1B 0x00 not programmed
0x1C 0x00 not programmed
0x19 0x00 not programmed
0x1a 0x00 not programmed
0x0F 0x01 not programmed

The dig_if_reset is not at all programmed in the eval board. Request you to clarify on how to achieve synchronization across multiple devices.