Problems with AD7142 SPI Communications


we are planning an to use the AD7142 for our application and thus would like to evaluate the chip. So we soldered the chip to a prototype board and connected it to the SPI bus of a uC Evaluation board. Unfortuantely we did not manage to get the SPI communication running properly. The chip's MISO line usually stays low if we try to read any register. I wonder if we are doing the start up sequence wrong. Is it possible to read any registers before Bank 2 and Bank 1 registers have been written correctly?

An interresting observation: When we completely disconnect the chip from Supply and SPI-Bus and reconnect it afterwards, the SPI communication actually seems to work, which means we can write any register and read that value afterwards from it. However instead of delivering a square wave the excitation source remains on supply level. It can be deactivated though, by writing to register 0x00. In addition, the registers do not hold their default values (except for the Device adress register 0x17) and most writes do not have any effect (writing the reset bit in register 0x00 for example does not reset the device and the bit is not cleard).

We would really appriciate any help!

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