此问题之前已被问过，但我仍然无法解决代码中的问题。我的代码有什么问题，这是警告吗？
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.all;
use work.switch_param.all;
entity fault_gen is
port (
clk : in std_logic;
rst : in std_logic;
buff_free : in std_logic;
i_fault_gen : in std_logic_vector(NUM_PORTS -1 downto 0);
o_sel : out std_logic_vector(NUM_PORTS -1 downto 0);
o_valid : out std_logic;
o_fault_gen : out flit_t
);
end fault_gen;
architecture Behavioral of fault_gen is
type ftgen_state is (idle, compt, final);
signal current_state, next_state : ftgen_state;
signal ft_current, ft_next : flit_t;
signal temp_gen : std_logic_vector(FT_INFO_BITS - 1 downto 0);
signal enable : std_logic;
begin
proc_state: process(clk, rst)
begin
if (rst = '1') then
current_state <= idle;
ft_current <= (others => '0');
elsif (clk'event and clk='1') then
current_state <= next_state;
ft_current <= ft_next;
end if;
end process proc_state;
proc_fault: process(current_state, ft_current, i_fault_gen, buff_free)
begin
temp_gen <= (others => '0');
o_sel <= (others => '0');
o_valid <= '0';
enable <= '0';
ft_next <= ft_current;
case current_state is
when idle =>
if (buff_free = '1') then
if (i_fault_gen = (i_fault_gen'range => '0')) then
next_state <= idle;
else
next_state <= compt;
end if;
else
next_state <= idle;
end if;
when compt =>
next_state <= final;
ftgen_inst: for i in NUM_PORTS -1 downto 0 loop
if (i_fault_gen(i) = '1') then
temp_gen <= std_logic_vector(to_unsigned(i,FT_INFO_BITS));
o_sel(i) <= '1';
enable <= '1';
exit ftgen_inst;
end if;
end loop; -- i
when final =>
next_state <= idle;
if (enable = '1') then
ft_next <= FT_INFO & link_fault & temp_gen & switch_ID & reserved_bits;
o_valid <= '1';
else
next_state <= idle;
end if;
when others =>
next_state <= idle;
end case;
end process proc_fault;
o_fault_gen <= ft_current;
end Behavioral;
在此程序中，信号temp_gen的值正在变化，其余参数不变。
开关参数是：
package switch_param is
constant NUM_PORTS : natural := 5;
constant FLIT_WIDTH : natural:= 36;
subtype flit_t is std_logic_vector(FLIT_WIDTH - 1 downto 0);
constant FT_INFO : std_logic_vector(3 downto 0) := "0011";
constant link_fault : std_logic_vector(2 downto 0) := "000";
constant reserved_bits : std_logic_vector(17 downto 0) := (others => '0');
constant FT_INFO_BITS : integer := 3;
constant switch_ID : std_logic_vector(7 downto 0) := "11111111"; -- switch ID
end switch_param;
警告是：
WARNING:Xst:2404 - FFs/Latches <ft_current<35:34>> (without init value) have a constant value of 0 in block <fault_gen>.
WARNING:Xst:1710 - FF/Latch <ft_current_31> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_30> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_29> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_17> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_16> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_15> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_14> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_13> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_12> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_11> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_10> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_9> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_8> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_7> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_6> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_5> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_4> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_3> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_2> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_1> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_0> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch <ft_current_18> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_26> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_27> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_28> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch <ft_current_18> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_26> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_27> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_28> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch <ft_current_18> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_26> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_27> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_28> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch <ft_current_18> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_26> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_27> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <ft_current_28> (without init value) has a constant value of 0 in block <fault_gen>. This FF/Latch will be trimmed during the optimization process.
答案 0 :(得分：2)
从包裹值中我生成了这个：
-- Field Size Contents ft_next range static?
------------------------------------------------------------------------
-- FT_INFO (3 downto 0) "0011" 35 downto 32 static
-- link_fault (2 downto 0) "000" 31 downto 29 static
-- temp_gen (2 downto 0) "011" 28 downto 26 changeable
-- switch_ID (7 downto 0) "11111111" 25 downto 18 static
-- reserved_bits (17 downto 0) (other s=> '0') 17 downto 0 static
ft_next <= FT_INFO & link_fault & temp_gen & switch_ID & reserved_bits;
只有三个非静态位分配给ft_next（temp_gen - 可能的值“100”，“011”，“010”，“001”和“000”）。
所有其余的局部静态（在分析时已知），这意味着它们不需要触发器。你最终得到了三个。
我最初得到了向后TO_UNISIGNED参数的顺序，但在完成之后（并且它告诉你验证你在答案中依赖的所有内容）你会注意到循环：
when compt =>
next_state <= final;
ftgen_inst: for i in NUM_PORTS -1 downto 0 loop
if (i_fault_gen(i) = '1') then
temp_gen <= std_logic_vector(to_unsigned(i,FT_INFO_BITS));
o_sel(i) <= '1';
enable <= '1';
exit ftgen_inst;
end if;
end loop; -- i
在流程语句中分配信号的一个特征是信号只有一个未来值。这意味着最后一个带有'1'的fault_gen（i）是实际报告的那个，优先级递增到0。你可以考虑将temp_gen替换为i_fault_gen，这是不可接受的。
无论如何，你定义ft_next的方式，只需要三个触发器，其余的位都是静态的。