Rob,

One correction in my earlier post.

The CVref calculation for High Range is CVREF = (VDD/4) + (VR3:VR0 X VDD/32).
Using your input values of VDD=3.3 and VR3:VR0=8, the calculation will come out like this.
(3.3/4) + (8 x (3.3/32) = (0.825) + (8 x 0.103125) = (0.825) + (0.825) = 1.65 Vdc

If you use Low Range then here is the info:
CVREF = (VR3:VR0/24) x VDD = (8/24) x 3.3 = 0.333 x 3.3 = 1.1 Vdc

Regards,