我正在做一个学习VHDL的小项目。目前我正在研究 BCD 转换器（将二进制转换为其 BCD 数字）。
但是在实现测试平台时我被卡住了。应用模式后，它不会重置输出。
我的实体 VHDL 代码：
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity bcd_mod is
port (
entry: in std_logic_vector(16 downto 0);
outp: out std_logic_vector(20 downto 0)
);
end bcd_mod;
architecture calculate of bcd_mod is
begin
process(entry)
variable outp_cp : std_logic_vector(20 downto 0) := (others => '0');
variable place : integer := 1;
variable digit : integer := 0;
variable number : integer := 0;
begin
for i in 16 downto 0 loop
case entry(i) is
when '0' => null;
when '1' => number := number + (2**i);
when others => null;
end case;
end loop;
if number > 99999 then
outp_cp(20) := '1';
else
while (number > 0) loop
digit := number mod 10;
if place = 1 then
outp_cp(3 downto 0) := std_logic_vector(to_unsigned(digit, 4));
elsif place = 2 then
outp_cp(7 downto 4) := std_logic_vector(to_unsigned(digit, 4));
elsif place = 3 then
outp_cp(11 downto 8) := std_logic_vector(to_unsigned(digit, 4));
elsif place = 4 then
outp_cp(15 downto 12) := std_logic_vector(to_unsigned(digit, 4));
else
outp_cp(19 downto 16) := std_logic_vector(to_unsigned(digit, 4));
end if;
number := number - digit;
number := number / 10;
place := place + 1;
end loop;
end if;
outp <= outp_cp;
outp_cp := (others => '0');
end process;
end calculate;
我的代码测试台：
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity bcd_mod_testbench is
end bcd_mod_testbench;
architecture calculate of bcd_mod_testbench is
component bmt
port(entry : in std_logic_vector(16 downto 0); outp : out std_logic_vector(20 downto 0));
end component;
for bmt_0: bmt use entity work.bcd_mod;
signal entry : std_logic_vector(16 downto 0);
signal outp : std_logic_vector(20 downto 0);
begin
bmt_0: bmt port map (entry => entry, outp => outp);
process
type pattern_type is record
entry : std_logic_vector(16 downto 0);
outp : std_logic_vector(20 downto 0);
end record;
type pattern_array is array (natural range <>) of pattern_type;
constant patterns : pattern_array :=
(("00000110111101101", "000000011010101100101"),
("00000000000000011", "000000000000000000011"),
("00000000000011011", "000000000000000100111"));
begin
for i in patterns'range loop
entry <= patterns(i).entry;
wait for 1 ns;
assert outp = patterns(i).outp
report "Wrong BCD number." severity error;
end loop;
assert false report "End of test." severity note;
wait;
end process;
end calculate;
这是 GTKWave 中的输出。您可以在此处看到，在使用大数字运行代码后，以下数字从之前的数字结束的位置开始。
（可点击）
希望得到任何提示来解决这个问题。