水电之家讯：8位移位寄存器LIBRARY ieee;
USE ieee.std_logic_1164.all;
ENTITY shifter IS
PORT (
data_in: IN STD_LOGIC_VECTOR(7 DOWNTO 0);--输入的数据
n: IN STD_LOGIC_VECTOR(2 DOWNTO 0);--移位的数量
dir: IN STD_LOGIC--移动的方向 0:左 1:右
kind: IN STD_LOGIC_VECTOR(1 DOWNTO 0)；--移动类型 00:算术移 01:逻辑移 10:循环移
clock: IN BIT；--手动时钟PULSE
data_out: OUT STD_LOGIC_VECTOR(7 DOWNTO 0)--移位的结果
);
END shifter;ARCHITECTURE behav of shifter IS
BEGIN
PROCESS (data_in, n, dir, kind)
VARIABLE x,y : STD_LOGIC_VECTOR(7 DOWNTO 0);
VARIABLE ctrl0,ctrl1,ctrl2 : STD_LOGIC_VECTOR (3 DOWNTO 0);
BEGIN
IF (clock'EVENT AND clock = '1')THEN--产生控制向量ctrl
ctrl0 := n(0) & dir & kind(1) & kind(0);
ctrl1 := n(1) & dir & kind(1) & kind(0);
ctrl2 := n(2) & dir & kind(1) & kind(0);
ctrl2 := n(2) & dir & kind(1) & kind(0);
CASE ctrl0 IS
WHEN "0000" | "0001" | "0010" | "0100" | "0101" | "0110" => x := data_in; --n=0时不移动
WHEN "1000" => x := data_in(6 DOWNTO 0) & data_in(0);--算术左移1位
WHEN "1001" => x := data_in(6 DOWNTO 0) & '0';--逻辑左移1位
WHEN "1010" => x := data_in(6 DOWNTO 0) & data_in(7); --循环左移1位
WHEN "1100" => x := data_in(7) & data_in(7 DOWNTO 1);-算术右移1位
WHEN "1101" => x := '0' & data_in(7 DOWNTO 1);--逻辑右移1位
WHEN "1110" => x := data_in(0) & data_in(7 DOWNTO 1);--循环右移1位
WHEN others => null;
END CASE;
CASE ctrl1 IS
WHEN "0000" | "0001" | "0010" | "0100" | "0101" | "0110" => y := x; --n=0时不移动
WHEN "1000" => y := x(5 DOWNTO 0) & x(0) & x(0);--算术左移2位
WHEN "1001" => y := x(5 DOWNTO 0) & "00";--逻辑左移2位
WHEN "1010" => y := x(5 DOWNTO 0) & x(7 DOWNTO 6);--循环左移2位
WHEN "1100" => y := x(7) & x(7) & x(7 DOWNTO 2);--算术右移2位
WHEN "1101" => y := "00" & x(7 DOWNTO 2);--逻辑右移2位
WHEN "1110" => y := x(1 DOWNTO 0) & x(7 DOWNTO 2);--循环右移2位
WHEN others => null;
END CASE;CASE ctrl2 IS
WHEN "0000" | "0001" | "0010" | "0100" | "0101" | "0110" => data_out <= y; --n=0时不移动
WHEN "1000" => data_out <= y(3 DOWNTO 0) & y(0) & y(0) & y(0) & y(0); --算术左移4位
WHEN "1001" => data_out <= y(3 DOWNTO 0) & "0000"; --逻辑左移4位
WHEN "1010" | "1110" => data_out <= y(3 DOWNTO 0) & y(7 DOWNTO 4);--循环左(右)移4位
WHEN "1100" => data_out <= y(7) & y(7) & y(7) & y(7) & y(7 DOWNTO 4);--算术右移4位
WHEN "1101" => data_out <= "0000" & y(7 DOWNTO 4);--逻辑右移4位
WHEN others => null;
END CASE;
END IF;
END PROCESS;
END behav;
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