Question

有些人可以解释为什么我在这段代码中出现语法错误。

An <= "1110" when anode = "00" else
AN <= "1101" when anode = "01" else
An <= "1011" when anode = "10" else 
An <= "0111" when anode = "11";

segment <= counter_1r    when anode = "00" else
segment <= counter_10r   when anode = "01" else
segment <= counter_100r  when anode = "10" else
segment <= counter_1000r When anode = "11";

它说

ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 181. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 182. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 183. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 181. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 182. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 183. Type of An is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 186. Type of segment is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 187. Type of segment is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 188. Type of segment is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 186. Type of segment is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 187. Type of segment is incompatible with type of <=.
ERROR:HDLParsers:800 - "C:/.Xilinx/Stopur/main.vhd" Line 188. Type of segment is incompatible with type of <=.

我不明白，因为在我的代码中我已经将我实体中所有受影响的元素设置为输出，它们都使用相同的类型。

PORT(
    CLK: in std_logic;
--  LED: out std_logic_vector (7 downto 0);
--  Switch: in std_logic_vector(7 downto 0);
    Segment: out std_logic_vector (7 downto 0); 
    AN: out std_logic_vector (3 downto 0) 
);
end Main;

architecture Behavioral of Main is
    signal counter_1000:  integer range 0 to 9;
    signal counter_100:   integer range 0 to 9;
    signal counter_10:    integer range 0 to 9;
    signal counter_1:     integer range 0 to 9;
    signal counter_1r:    std_logic_vector(7 downto 0);
    signal counter_10r:   std_logic_vector(7 downto 0);
    signal counter_100r:  std_logic_vector(7 downto 0);
    signal counter_1000r: std_logic_vector(7 downto 0);
    signal prescaler:     integer range 0 to 50000000;
    signal limit:         integer range 0 to 50000000;
    signal Anode:         std_logic_vector(1 downto 0);
begin

Answer 1

条件信号分配（在过程之外）写为：

An <=
    "1110" when anode = "00" else
    "1101" when anode = "01" else
    "1011" when anode = "10" else 
    "0111" when anode = "11" else
    "0000";

segment <=
    counter_1r    when anode = "00" else
    counter_10r   when anode = "01" else
    counter_100r  when anode = "10" else
    counter_1000r When anode = "11" else
    "00000000";

在流程内部，您需要使用 if 语句或 case 语句。

Answer 2

要了解收到错误消息的原因，请查看以下代码：

An <= "1110" when anode = "00" else (AN <= "1101")....

else子句将被编译为AN与1101的比较，以查看它是否小于或等于。哪个类型为boolean，与An的类型（向量）不兼容。（我希望VHDL没有选择<=作为赋值运算符，但我们有！）

您需要的语法更像是这样（注意其他行上缺少<=）

An <= "1110" when anode = "00" else
      "1101" when anode = "01" else
      "1011" when anode = "10" else    
      "0111" when anode = "11" else
      null;

VHDL：“变量”的类型与＆lt; =的类型不兼容

2 个答案: