1). Basically, it is correct to divide the modulus / division. It is important to note that the signal trace should not cross the moat, and do not let the return current path of the power supply and signal become too large.
2). The crystal is a simulated positive feedback oscillator circuit with a stable oscillation signal that must meet the specifications of the loop gain and phase, and the oscillation specification of the analog signal is susceptible to interference, even if the ground guard traces may not be completely isolated interference. And too far away from the ground surface noise will also affect the positive feedback oscillator circuit. Therefore, we must be crystal and the chip into the distance may be close.
3). There are many conflicts between high-speed cabling and EMI requirements. But the basic principle is due to EMI plus the resistance capacitor or ferrite bead, can not cause some of the electrical characteristics of the signal does not meet the specifications. Therefore, it is best to use the alignment and PCB stacking techniques to solve or reduce EMI problems, such as high-speed signal to take the inner layer. Finally use a resistive capacitor or ferrite bead way to reduce the damage to the signal.
