How do you create functional block diagrams for schematic?

A design consists of various functional modules like memory, communication interface, power supply, and so on which interact together to build a comprehensive design. It is important to understand the relation between such interfaces to get a clear picture of the system. 

For a complex design, it is a good design practice to include functional block diagrams in the schematic. The diagram provides a high-level overview and helps designers interpret the end-to-end signal flow in the design. 

While we are aware of the importance of block diagrams, the question is, how do we best create block diagrams that are readable and at the same time, convey the right design intent? 

Let us know which of the following approaches will you take: 

1. One of the approaches is to create the block diagram outside the schematic tool and then embed it as an image in the schematic.
2. Use the inbuilt graphic shapes in the schematic tool. 
3. Usage of non-electrical parts for representing the block diagram. 
4. Or any other approach. 

What challenges do you come across while creating block diagrams?  

Any suggestion or recommendation that you would like to share with the design community to improve the block diagram creation process.

Team DesignTech
Cadence Design Systems