I have a design that uses a AD7656. I am reading the device in parallel byte mode. When I read the device I get a valid value for the high byte (I have HBEN =1) and what seems to be a valid value for the lower byte, except the lowest 3 bits are always 0. I am in +/- 10 volt range and sampling 1Ksps and reading the values back using a slow micro so there is not issues with the timing. When I look at the data lines on a scope, I see the upper byte bits and then nothing where the lower byte bits should be. I am using 5 channels and all the channels are acting the same. I get all 8 bits on the high byte read, but when reading the lower byte and get what appears to be good values expect the lower 3 bits are always zero.
I have replaced the chip, tried different read timing, checked voltages, etc. It is working (almost) so it seems like I am missing something.
Thank you for your help. Feel free to contact my via phone.