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LTC6804-2 IsoSPI communication issue

Category: Hardware
Product Number: LTC6804-2

I am working with the LTC6804 in a multi-drop configuration as part of a battery management system. Communication with the LTC6804-2 is via IsoSPI using an LTC6820 but I have not been able to read any data back from the device.

I have successfully communicated with an LTC6804 directly on a separate SPI bus so I don't think this is due to incorrect commands.

- The LTC6804 is powered with a 16V supply.

- I've enabled the watchdog timer and when communication begins, the Vdrive and Vreg voltages are enabled and operate to within the specifications in the datasheet. 

- Vref1 and Vref2 are always low, regardless of commands sent.

- The POL and PHA pins have all been pulled high and the MCU SPI bus settings configured to match.

- The MISO bus is pulled high through a 1k pullup resistor but never shows any data.

- The IsoSPI pulses are as expected on the IP/IM pins on the LTC6804.

Are there any steps you could suggest to continue debugging this issue?