VHDL案例/时:多个案例,单个子句

Question

在一个过程中,我有这样的事情:

CASE res IS
  WHEN "00" => Y <= A;
  WHEN "01" => Y <= A;
  WHEN "10" => Y <= B;
  WHEN "11" => Y <= C;
  WHEN OTHERS => Y <= 'X';
END CASE;

注意这种情况"00"并"01"获得相同的值.是否有类似的正确语法

WHEN "00", "01" => ？

额外注意:除了改变Y之外,还有更多内容,我只是为了简单起见而使用它.所以案例/何时是必要的.

Answer 1

您可以使用"管道"或条形符号分隔多个选项.您的示例的正确语法是:

CASE res IS
  WHEN "00" | "01" => Y <= A;
  WHEN "10" => Y <= B;
  WHEN "11" => Y <= C;
  WHEN OTHERS => Y <= 'X';
END CASE;

Answer 2

您还可以为案例提供一系列选择：

USE IEEE.STD_LOGIC_ARITH.ALL;

CASE CONV_INTEGER(res) IS
  WHEN 0 to 1 => Y <= A;
  WHEN 2 => Y <= B;
  WHEN 3 => Y <= C;
  WHEN OTHERS => Y <= 'X';
END CASE;