s2p2.vhd

来自「这是我做的I2C的vhdl程序和仿真和下载文件」· VHDL 代码 · 共 50 行

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

library IEEE;
use IEEE.Std_logic_1164.all;
use ieee.std_logic_arith.all;

ENTITY s2p2 IS
   PORT(
    nclr, 
    clock : IN std_logic;
    
    d: in std_logic;
    sr: out std_logic_vector( 7 downto 0)
  );
END s2p2;

ARCHITECTURE arc_p2s2 OF s2p2 IS

signal q :std_logic_vector(7 downto 0);
signal  cnt: unsigned(3 downto 0);

BEGIN
   PROCESS(d,nclr,clock)

   BEGIN

   IF nclr  = '0' THEN
      q <= "00000000";
       cnt<="0000";
   ELSE
      IF clock'EVENT AND clock = '1'      THEN
                                   q(0)<=d;
                                    cnt<="0000";
                                   
         FOR i IN 1 to 7 LOOP
                         q(i) <= q(i-1);
                         cnt<=cnt +1;
         END LOOP;
           if(cnt=8) then   
                          sr<=q;
                          cnt<="0000";
           end if;

      END IF;
   END IF;
   END PROCESS;
END arc_p2s2;