How Equations Use Expressions

Equations assign the value of an expression to a signal or set of signals in a logic description. The identifier and expression must follow the rules already established for those elements.

Equations use the assignment operators = and ?= (combinational), and := and ?:= (registered).

The complement operator, "!," can be used to express negative logic. The complement operator precedes the signal name and implies that the expression on the right of the equation is to be complemented before it is assigned to the signal. Use of the complement operator on the left side of equations is provided as an option; equations for negative logic parts can just as easily be expressed by complementing the expression on the right side of the equation.

Equations

When-Then-Else

Assignment Operators