There are some practical questions in the PCB design, you know?
First of all, EMI to consider from the system, PCB alone can not solve the problem. In the case of EMI, I think it is mainly to provide the shortest return path of the signal, reduce the coupling area and suppress differential mode interference. In addition, the formation is tightly coupled with the power layer and is better than the power layer to suppress common mode interference.
There are several reasons for paving copper in general. 1, EMC. for large area or power supply copper will play a shielding role, and some special, such as PGND play a protective role. 2, PCB process requirements. Generally, in order to ensure the effect of plating or laminating without deformation, copper is paved with less PCB boards. 3, signal integrity requirements, giving a high frequency digital signal a complete reflow path, and reducing the wiring of the DC network. Of course, there are heat dissipation, special device installation requirements, copper and so on.
In a system that contains DSP and PLD, what are the issues that should be noted when routing?
See the ratio of your signal speed to routing length. The signal integrity problem must be considered if the signal is in line with the time delay of the signal and the signal changes along the time. In addition, for a number of DSP, clock, data signal, line extension will also affect the quality and timing of the signal, need attention.