Programming an FPGA

Structure of a Design

HDLs are typically based around the idea of a module. A module is a circuit block that has some number of inputs and outputs and contains some logic to glue them together. A module could contain sub-modules or it could be stand-alone; similar to how a program is broken down into functions.

While it would be possible to put an entire design into a single module, it is better practice to use smaller modules to perform each piece of your design. By breaking down your project into modules, you simplify the complexity of any one piece you need to work on at any given time. Some modules can be made to perform common tasks and are used over and over again.

When you start a design, it is often helpful to draw out a block diagram showing the various modules and how they connect to each other. This helps define the scope of your design and break it down logically.

It can be difficult to drastically change the flow of an entire design once you start writing it so the more planning that goes into the overall architecture before starting the better.