shift_register_164.txt

来自「UART 的VHDL源代码。可在ISE, Max-Plus II,等开发环境下实」· 文本 代码 · 共 31 行

-- TTL164 Shift Register
-- download from: www.fpga.com.cn & www.pld.com.cn

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 q'RANGE LOOP
            IF i = 0 THEN q(i) <= (a AND b); 
            ELSE 
               q(i) <= q(i-1);
            END IF;
         END LOOP;
      END IF;
   END IF;
   END PROCESS;
END version1;