How to deal with some theoretical conflicts in actual wiring?
The crystal is a positive feedback oscillation circuit simulation, have stable oscillation signal, gain and loop must meet the phase specification, and the specification of this oscillation analog signal is vulnerable to interference, even with the ground guard traces may not be completely isolated interference. And too far away, the noise on the ground plane will also affect the positive feedback oscillation circuit. So make sure that the distance between the crystal and the chip is near.
Indeed, there are many conflicts between high-speed wiring and EMI requirements. But the basic principle is that, because of the resistor, capacitor or ferrite bead added by EMI, some electrical characteristics of the signal can not be met. Therefore, it is better to solve the problem of EMI by arranging the routing and PCB stacking techniques, such as high-speed signals coming in the inner layer. Finally, resistors, capacitors, or ferrite bead are used to reduce the damage to the signal.