dev164.vhd

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-- 74164 vhdl描述

library IEEE;
use IEEE.Std_logic_1164.all;

ENTITY dev164 IS
   PORT(a, b, nclr, clock : IN BIT;
         q : BUFFER BIT_VECTOR(0 TO 7));
END dev164;

ARCHITECTURE version1 OF dev164 IS
BEGIN
   PROCESS(a,b,nclr,clock)
   BEGIN
   IF nclr  = '0' THEN
      q <= "00000000";
   ELSE
      IF clock'EVENT AND clock = '1'
      THEN
     --     FOR i IN 1 to 7 LOOP           使用这结构编译有错
     --     if i=0 then q(i)<=(a AND b);
     --     else q(i) <= q(i-1);       
     --     END LOOP;       
          q(0) <= (a AND b);
         FOR i IN 1 to 7 LOOP
          q(i) <= q(i-1);       
         END LOOP;
      END IF;
   END IF;
   END PROCESS;
END version1;