Hey there,
First off, how do you know the 84 is sending? I would check to see that MISO and MOSI are connected properly (they are opposite on the 84, kinda confusing).
Also, I would make sure one of the devices has the "role pin" set to ground (I think that's how it worked?).
Let me know if you still can't get it to work, I can try to dig up some code