首先是这个简单的加法器实体:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_misc.all;
use ieee.numeric_std.all;
entity adder is
Port ( a : in STD_LOGIC_VECTOR(31 downto 0);
b : in STD_LOGIC_VECTOR(31 downto 0);
alu_out : out STD_LOGIC_VECTOR(31 downto 0) := (others => '0')
);
end adder;
architecture Behavioral of adder is
signal result_ext:STD_LOGIC_VECTOR(32 downto 0) := (others => '0');
signal result:STD_LOGIC_VECTOR(31 downto 0) := (others => '0');
begin
process (a,b)
begin
result_ext <= std_logic_vector(signed('0' & a) + signed('0' & b));
result <= result_ext(result'left downto 0);
alu_out <= result;
end process;
end Behavioral;
和测试台:
-- TestBench Template
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.numeric_std.ALL;
ENTITY testbench IS
END testbench;
ARCHITECTURE behavior OF testbench IS
signal a : STD_LOGIC_VECTOR(31 downto 0);
signal b : STD_LOGIC_VECTOR(31 downto 0);
signal alu_out : STD_LOGIC_VECTOR(31 downto 0);
BEGIN
ADDER : entity work.adder port map(
a => a,
b => b,
alu_out => alu_out
);
-- Test Bench Statements
tb : PROCESS
BEGIN
a <= B"0000_0000_0000_0000_0000_0000_0111_1010";
b <= B"0000_0000_0000_0000_0000_0000_0000_1011";
wait for 100 ns; -- wait until global set/reset completes
report "alu_out = " & integer'image(to_integer(signed(alu_out)));
wait; -- will wait forever
END PROCESS tb;
-- End Test Bench
END;
我得到报告输出:
Finished circuit initialization process.
at 100 ns: Note: alu_out = 0 (/testbench/).
如果我不初始化结果信号,我会得到未定义。所以问题是我最终没有得到结果。
我使用iSim和Xilinx。
此外,如果有人有一些关于 VHDL 的简短有效材料的良好链接,请随时发布。