See Also

The following statements are listed in the order in which they can appear in a Text Design File (.tdf). Declarations and statements within the Variable Section and Logic Section can be listed in any order, with the exception that the Defaults Statement must be the first statement within the Logic Section.

The following statements link to their corresponding syntax information. For other information about the statements, go to Design Structure.

• Title Statement
• Include Statement
• Constant Statement
• Define Statement
• Parameters Statement
• Function Prototype Statement
• Options Statement
• Assert Statement
• Subdesign Section
• Variable Section
  • Instance Declaration
  • Node Declaration
  • Register Declaration
  • State Machine Declaration
  • If Generate Statement
• Logic Section
  • Defaults Statement
  • Assert Statement
  • Boolean Equations
  • Boolean Control Equations
  • Case Statement
  • For Generate Statement
  • If Then Statement
  • If Generate Statement
  • In-Line Logic Function Reference
  • Truth Table Statement

AHDL is a concurrent language. All behavior specified in the Logic Section of a TDF is evaluated at the same time rather than sequentially. Equations that assign multiple values to the same AHDL node or variable are logically connected (ORed if the node or variable is active high, ANDed if it is active low).

A TDF must contain a Subdesign Section and a Logic Section. It can optionally contain a single Variable Section, Options Statement, Title Statement, and Defaults Statement; and one or more Include, Parameters, Constant, Define, and Function Prototype Statements.

The last entries in a TDF are the Subdesign Section, Variable Section (optional), and Logic Section, which together comprise the behavioral description of the TDF.

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