-- Copyright © 1993 by  McGraw-Hill, Inc. and Zainalabedin Navabi

-- FIGURE 7.43 




-- ENTITY DECLERATION OF TEST BENCH FOR XNOR :

ENTITY test_xnor IS END test_xnor; 
--



-- WIRING AND TESTING XNOR WITH 4 OPEN COLCCTOR NAND GATES :

USE WORK.basic_utilities.ALL;
ARCHITECTURE input_output OF test_xnor IS
  COMPONENT sn7403 
    PORT (a1, a2, a3, a4, b1, b2, b3, b4 : IN qit; y1, y2, y3, y4 : OUT qit);
  END COMPONENT;
  FOR ALL : sn7403 USE ENTITY WORK.sn7403 (structural);
  SIGNAL aa, bb : qit;
  SIGNAL pull_up_1, pull_up_2, pull_up_3 : anded_qit := 'Z';
BEGIN
  aa <= '1', '0' AFTER 10US, '1' AFTER 30US, '0' AFTER 50US, 'Z' AFTER 60US; 
  bb <= '0', '1' AFTER 20US, '0' AFTER 40US, 'Z' AFTER 70US;
  c1: sn7403 PORT MAP (aa        , bb        , pull_up_1 , pull_up_2, 
                       aa        , bb        , bb        , aa       ,
                       pull_up_1 , pull_up_2 , pull_up_3 , pull_up_3 );
END input_output; 
--