AD5758 MISO ISNOT RESPONDING

Hi Team,

We are working on AD5758 in one of our project below are the issues we are facing.

(Note: for references we are attaching the schematic-R369 is Shorted and we are using external VREF Voltage, C192,C118,C392 are DNP)

1. we checked the proper voltages to IC, it found OK.

2. We have developed the VHDL code on CYCLONE V FPGA in Intel Altera Tool.

3. i followed and developed code as per datasheet (Page 52 and 53) to find out the DAC value.

4. i send the data like "SLIPTBIT,AD1,AD0,REGISTER_ADDRESS,DATA,CRC".

5. once i send the above format, fault is going from ACTIVE HIGH to ACTIVE LOW. 

6. To check proper CRC, we checked 256 possible conditions (CRC 8 bits range from 0-255), but for every condition fault is going to from ACTIVE HIGH to ACTIVE LOW. 

7. Due to that issue, we are unable to get MISO data, it shows always ACTIVE HIGH.

8. SCLK frequency is 10MHz we initially worked, now we reduced to 1MHz, but there is NO CHANGE and the same issue been repeating.

9. we tried with both HARDWARE RESET AND SOFTWARE RESET.

10. we checked timing parameters.

11. finally, we used SPI 3 wire interface IPs and done all above steps, but issue is same.

could you please tell me how to get MISO data and how to rectify fault issue.

if fault issue is from CRC error only, how to resolve it and how to generate and compute CRC??

please give us your valuable advises, what and where we have done mistakes.

thank you

regards

RAJU CHIMMI