Hi Dan
I would be willing to assist you with your query. It is definitely strange that you are not able to read back 0x01 when you read the RUN register, even after you have set it to 0x01. One way to check if the DSP is running or not is to read energy registers or RMS registers and see if you are reading back anything( if they are getting updated every 8KHz). If yes, then DSP is running and in that case, you are not reading back 0x01 correctly. There is nothing in the chip that would stop you from reading back the RUN register. If you see that the energy and RMS registers aren't updating, then the RUN register is truly at 0x00 and this means that your write operation to the RUN register was unsuccessful. Refer to page 75 of Rev.H datasheet to see in which order you must initialize the registers.However, this seems to be a communication problem to me, at this point.
When you read/write other registers, do you always get back good values or have you noticed occasional issues? Which registers have you read and which ones have you written with non-default values? Have you analyzed the SPI signals on scope to see if there is anything wrong? Try writing/ reading back multiple times to see if the results are any different. What is the SPI clock frequency? Are there any isolators used on the SPI lines?
Regards
hmani