VHDL Programming

built into the language and therefore in VHDL93 it can be used and over-

loaded. The example here shows a use of the XNORoperator.

ENTITY xnor2 IS

GENERIC( delay : TIME);

PORT( a, b : IN STD_LOGIC;

q : OUT STD_LOGIC);

END ENTITY xnor2;

ARCHITECTURE behave OF xnor2 IS

BEGIN

a <= a XNOR b AFTER delay;

END ARCHITECTURE behave;

This example shows a 2-input xnorgate using the built-in XNOR

operator. The XNORoperator can be overloaded to work with any types. In

this example two STD_LOGICtype values are xnor’ed together to form the

final result.

Appendix D: VHDL93 Updates 467