AHDL

Implementing Boolean Expressions & Equations



Boolean expressions are sets of nodes, numbers, constants, and other Boolean expressions, separated by operators and/or comparators, and optionally grouped with parentheses. A Boolean equation sets a node or group equal to the value of a Boolean expression.

The boole1.tdf file shown below shows two simple Boolean expressions that represent two logic gates.

SUBDESIGN boole1
(
   a0, a1, b  : INPUT;
   out1, out2 : OUTPUT;
)
BEGIN
   out1 = a1 & !a0;
   out2 = out1 # b;
END;

In this sample file, the out1 output is driven by the logical AND of a1 and the inverse of a0, and the out2 output is driven by the logical OR of out1 and b. Since these equations are evaluated concurrently, their order in the file is not important.


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