The communication can go in both directions between the PDMs. For instance you could set up a CAN output on PDM1 to send an input voltage. The on PDM2 you could set up a CAN input to receive that CAN frame and use the data as needed. The same would work in the other direction too, you just need to make sure that each PDM is sending the CAN frames with different IDs to the other.
The communication can go in both directions between the PDMs. For instance you could set up a CAN output on PDM1 to send an input voltage. The on PDM2 you could set up a CAN input to receive that CAN frame and use the data as needed. The same would work in the other direction too, you just need to make sure that each PDM is sending the CAN frames with different IDs to the other.