我如何在程序中放置IF循环

Question

我正在编写一个执行以下操作的程序：

目的：要在屏幕上移动图像。

输入：8 x 8图像

命令：00-向右移动； 01-向左移动； 10-向上移动； 11-向下滚动。

由于我是VHDL的新手，所以我需要一些帮助。

library ieee;  
 use ieee.std_logic_1164.all;  
 use ieee.numeric_std.all;  

 entity imagem is  
  port(A,B,C,D,E,F,G,H : in unsigned(7 downto 0);  
      SEL : in unsigned(1 downto 0);  
       OTA,OTB,OTC,OTD,OTE,OTF,OTG,OTH: out unsigned(7 downto 0));  
 end imagem;  

architecture img of imagem is  
   begin  
     if SEL = "00"  then

        OTA <= A sll 1 ;
    OTB <= B sll 1 ; 
    OTC <= C sll 1 ; 
    OTD <= D sll 1 ; 
    OTE <= E sll 1 ; 
    OTF <= F sll 1 ; 
    OTG <= G sll 1 ; 
    OTH <= H sll 1 ; 

      elsif SEL = "01" then

    OTA <= A srl 1 ;
    OTB <= B srl 1 ; 
    OTC <= C srl 1 ; 
    OTD <= D srl 1 ; 
    OTE <= E srl 1 ; 
    OTF <= F srl 1 ; 
    OTG <= G srl 1 ; 
    OTH <= H srl 1 ; 

      elsif SEL = "10" then

    OTA <= B ;
    OTB <= C ; 
    OTC <= D ; 
    OTD <= E ; 
    OTE <= F ; 
    OTF <= G ; 
    OTG <= H ; 
    OTH <= "00000000" ; 

      else 

    OTA <= "00000000" ;
    OTB <= A ; 
    OTC <= B ; 
    OTD <= C ; 
    OTE <= D ; 
    OTF <= E ; 
    OTG <= F ; 
    OTH <= G ; 
      end if;       
 end img;

Answer 1

要使IF语句正常工作，请将其放在进程中...

library ieee;  
 use ieee.std_logic_1164.all;  
 use ieee.numeric_std.all;  

 entity imagem is  
  port(A,B,C,D,E,F,G,H : in unsigned(7 downto 0);  
      SEL : in unsigned(1 downto 0);  
       OTA,OTB,OTC,OTD,OTE,OTF,OTG,OTH: out unsigned(7 downto 0));  
 end imagem;  

architecture img of imagem is  
begin
process (SEL)
   begin  
     if SEL = "00"  then

        OTA <= A sll 1 ;
        OTB <= B sll 1 ; 
        OTC <= C sll 1 ; 
        OTD <= D sll 1 ; 
        OTE <= E sll 1 ; 
        OTF <= F sll 1 ; 
        OTG <= G sll 1 ; 
        OTH <= H sll 1 ; 

      elsif SEL = "01" then

        OTA <= A srl 1 ;
        OTB <= B srl 1 ; 
        OTC <= C srl 1 ; 
        OTD <= D srl 1 ; 
        OTE <= E srl 1 ; 
        OTF <= F srl 1 ; 
        OTG <= G srl 1 ; 
        OTH <= H srl 1 ; 

      elsif SEL = "10" then

    OTA <= B ;
    OTB <= C ; 
    OTC <= D ; 
    OTD <= E ; 
    OTE <= F ; 
    OTF <= G ; 
    OTG <= H ; 
    OTH <= "00000000" ; 

      else 

    OTA <= "00000000" ;
    OTB <= A ; 
    OTC <= B ; 
    OTD <= C ; 
    OTE <= D ; 
    OTF <= E ; 
    OTG <= F ; 
    OTH <= G ; 
      end if; 
end process;

 end img;