if a = '0' and b ='0' and c='0' then limit <= 0; elsif a = '0' and b ='0' and c='1' then limit <= 1; elsif a = '0' and b ='1' and c='0' then limit <= 2; elsif a = '0' and b ='1' and c='1' then limit <= 3; elsif a = '1' and b ='0' and c='0' then limit <= 4; elsif a = '1' and b ='0' and c='1' then limit <= 5; elsif a = '1' and b ='1' and c='0' then limit <= 6; elsif a = '1' and b ='1' and c='1' then limit <= 7; end if;如何简化

可以使用二进制直接将abc转换成一个数字，因为abc组合只有8种，可以将其编码为0~7的8个数字。可以使用以下代码简化原始代码：

limit <= to_integer(unsigned(a & b & c));

其中 "&" 是按位与操作符，将a、b、c按位连接后再使用 unsigned 将其转换为无符号整数，最后使用 to_integer 将其转换为有符号整数，即可得到0~7的数字，从而实现了上述条件的判断。

相关问题

if a = '0' and b ='0' and c='0' then limit <= 0; elsif a = '0' and b ='0' and c='1' then limit <= 1; elsif a = '0' and b ='1' and c='0' then limit <= 2; elsif a = '0' and b ='1' and c='1' then limit <= 3; elsif a = '1' and b ='0' and c='0' then limit <= 4; elsif a = '1' and b ='0' and c='1' then limit <= 5; elsif a = '1' and b ='1' and c='0' then limit <= 6; elsif a = '1' and b ='1' and c='1' then limit <= 7; end if;如何用vhdl语言简化

可以使用`to_integer`和`unsigned`函数结合使用来简化这段代码。具体实现如下：

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

entity example is
    port (
        a, b, c : in  std_logic;
        limit : out integer range 0 to 7
    );
end entity example;

architecture rtl of example is
begin
    limit <= to_integer(unsigned(a & b & c));
end architecture rtl;

在这个例子中，我们声明了一个名为`example`的实体，它有三个输入端口（`a`，`b`，`c`）和一个输出端口（`limit`），它是一个`integer`类型的值，范围在0到7之间。在体系结构中，我们使用`&`运算符将`a`，`b`和`c`连接成一个单独的`std_logic_vector`向量，然后使用`unsigned`函数将其转换为无符号整数类型。最后，我们使用`to_integer`函数将无符号整数类型转换回`integer`类型，并将其传递给`limit`输出端口。

case st is when st0=>en1<='0';green<='0';red<='0';sp<='0'; if start='1'then st<=st1; else st<=st0; end if; when stl=>en1<='1';green<='0';red<='0';sp<='0'; if result='1'then st<=st2; elsif iopen=′1'then st<=st4; elsif set='1'then st<=st0; else st<=stl; end if; when st2=>en1<='1';green<='0';red<='0';sp<='0'; if iopen=′1′then st<=st3; elsif set='1′then st<=st0; else st<=st2; end if; when st3=>en1<='0';green<='1';red<='0';sp<='0'; if set=′1′then st<=st0; else st<=st3; end if; when st4=>en1<='1';green<='0';red<='1';sp<='0'; if result=′1′then st<=st2; elsif set=′1′then st<=st0; elsif result=′0′and iopen=′1′then st<=st5; else st<=st4; end if; when st5=>en1<='0';green<='0';red<='1';sp<='1'; if set='1'then st<=st0; else st<=st5; end if; when others=>st<=st0; end case;这段代码错误在哪，并帮我改正

这段代码的错误在于if语句应该被放在process块中，而不是在case块中。此外，'和′是不同的符号，应该使用正确的符号。以下是修改后的代码：

process(st, start, result, iopen, set)
begin
   case st is 
      when st0=>
         en1<='0';
         green<='0';
         red<='0';
         sp<='0';
         if start='1' then 
            st<=st1;
         else 
            st<=st0;
         end if; 
      when stl=>
         en1<='1';
         green<='0';
         red<='0';
         sp<='0';
         if result='1' then 
            st<=st2;
         elsif iopen='1' then 
            st<=st4;
         elsif set='1' then 
            st<=st0;
         else 
            st<=stl;
         end if;    
      when st2=>
         en1<='1';
         green<='0';
         red<='0';
         sp<='0';
         if iopen='1' then 
            st<=st3;
         elsif set='1' then 
            st<=st0;
         else 
            st<=st2;
         end if; 
      when st3=>
         en1<='0';
         green<='1';
         red<='0';
         sp<='0';
         if set='1' then 
            st<=st0;
         else 
            st<=st3;
         end if; 
      when st4=>
         en1<='1';
         green<='0';
         red<='1';
         sp<='0';
         if result='1' then 
            st<=st2;
         elsif set='1' then 
            st<=st0;
         elsif result='0' and iopen='1' then 
            st<=st5;
         else 
            st<=st4;
         end if; 
      when st5=>
         en1<='0';
         green<='0';
         red<='1';
         sp<='1';
         if set='1' then 
            st<=st0;
         else 
            st<=st5;
         end if; 
      when others=>
         st<=st0; 
   end case; 
end process;

请注意，代码中仍然可能存在其他错误，因此您应该进行仔细的测试和验证。