Adding 32kHz crystal?

[morrowa]

I'm interested in using a 32768Hz external crystal to enable modem sleep during light sleep.

I see in the schematic and PCB layout that there are unpopulated pads for a 32768Hz crystal along with supporting passives. However, I could not find any information on the part values.

What are the required values/tolerances for R12, C12, C13, and Y1?

Thank you!