probably uses a schmitt trigger invertor. the crystal is connected from the input to the output of the invertor. Typically each side of the crystal as a small capacitor to ground. The value of the capacitor depends on the crystal, they will have a spec, 18pf, 30pf etc. The value you use, has to take in the capacitance of the IC input/output pins.
Say you have a 18 pf crystal, and the IC has 6pf to ground. The crystal would see 3 pf across it (6pf in series with 6pf). that means you need another 15 pf. If you tie a 30 pf cap to ground on each end of the Cap, you get 15pf (30pf series 30 pf=15pf)