Hi Peter,
If you set it to 360 degrees, the D1 bit in the fault register can still be set. The reason behind this is - should the phase lock range is set to 360 degrees, the accuracy of the AD2S1210 is not affected if the phase between the excitation and the sine cosine signals does not exceed +/-44 degree. If you pass this range, the synthetic reference does not correct for the difference in phase beyond +/-44 degrees. The remaining phase difference will cause additional inaccuracy dependent on the phase, excitation frequency and rotation speed. You can find the its relationship to the equation found on Page 18 of the datasheet.
The part will compensate up to +/-44 degrees to less than 10 degrees of phase shift. Anything above this causes additional error.
Also to be aware if the phase lock range is set to 360 degrees and a LOS occurs, a reset must be issued to the AD2S1210 or else there is the risk that the position output will be 180 Degrees out of phase when the signals are reconnected.
Regards,
Johnny