Chapter 3

Structural Descriptions

A Verilog circuit description can be one of two types; a structural description or a functional description, also referred to as a Register Transfer Level (RTL) description. A structural description defines the exact physical makeup of the circuit, detailing components and the connections between them. A functional or RTL description describes a circuit in terms of its registers and the combinatorial logic between the registers.

This chapter describes the construction of structural descriptions and is divided into the following sections.

• “Modules”
  
  
• “Macromodules”
  
  
• “Port Definitions”
  
  
• “Port Names”
  
  
• “Module Statements and Constructs”
  
  
• “Module Instantiations”