8位双向移位寄存器的设计与实现

--IEEE库及其中程序包的使用说明 LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL; --实体的说明 ENTITY SHIFTER IS PORT(DATA:IN STD_LOGIC_VECTOR(7 DOWNTO 0); SHIFT_LEFT:IN STD_LOGIC; SHIFT_RIGHT:IN STD_LOGIC; RESET:IN STD_LOGIC; MODE:IN STD_LOGIC_VECTOR(1 DOWNTO 0); CLK:IN STD_LOGIC; QOUT:BUFFER STD_LOGIC_VECTOR(7 DOWNTO 0)); END SHIFTER; --结构体的说明 ARCHITECTURE ART OF SHIFTER IS BEGIN PROCESS BEGIN WAIT UNTIL(RISING_EDGE(CLK));--条件等待语句，时钟上跳沿到达脱离挂起状态 IF(RESET='0')THEN --复位 QOUT<="00000000"; ELSE CASE MODE IS WHEN "01"=>QOUT<=SHIFT_RIGHT&QOUT(7 DOWNTO 1); --右移一位 WHEN "10"=>QOUT<=QOUT(6 DOWNTO 0)&SHIFT_LEFT; --左移一位 WHEN "11"=>QOUT<=DATA; -- WHEN OTHERS=>NULL; END CASE; END IF; END PROCESS; END ART;