在VHDL中出现“错误:未声明'r_cnt'“，如何解决

出现“错误:未声明'r_cnt'”通常意味着您的代码中使用了未声明的变量r_cnt。解决此问题的方法是在代码中声明该变量。

在VHDL中，变量可以声明在过程（process）内部或架构（architecture）内部。如果您已经在架构内声明了变量，但仍然出现了“未声明”错误，请确保：

1. 您在使用变量之前已经声明了它；
2. 声明变量的作用域覆盖了使用变量的代码行。

例如，如果您在架构内部声明了变量r_cnt，并且要在某个过程内使用它，您需要确保该过程在声明变量r_cnt的架构内部。

如果您仍然无法解决此问题，请检查您的代码，确保您正确地拼写了变量名称。如果变量名称有误，则会出现“未声明”错误。

相关问题

讲下面这个Verilog文件转化为VHDL文件“module Serial_output( input i_clk , input i_rst , input i_T_valid , input signed[9:0] i_T , input [3 :0] i_Device_ID , output reg o_Serial_data ); reg Frame_valid = 1'd0 ; reg [13:0] Frame = 13'd0; always @(posedge i_clk)begin if(i_rst == 1'b1)begin Frame_valid <= 1'd0 ; Frame <= 13'd0; end else if(i_T_valid)begin Frame_valid <= 1'b1 ; Frame <= {i_Device_ID,i_T}; end else Frame_valid <= 1'd0 ; end reg [2:0] s_Frame_valid = 3'd0; always @(posedge i_clk)begin s_Frame_valid <= {s_Frame_valid[1:0],Frame_valid}; end reg [4:0] r_bit_cnt = 5'd0; always @(posedge i_clk)begin if(i_rst == 1'b1) r_bit_cnt <= 5'd0; else if(s_Frame_valid[2]) r_bit_cnt <= 5'd0; else if(r_bit_cnt >= 5'd13) r_bit_cnt <= r_bit_cnt; else r_bit_cnt <= r_bit_cnt + 1'b1; end always @(*)begin case (r_bit_cnt) 5'd0 :o_Serial_data <= Frame[13] ; 5'd1 :o_Serial_data <= Frame[12] ; 5'd2 :o_Serial_data <= Frame[11] ; 5'd3 :o_Serial_data <= Frame[10] ; 5'd4 :o_Serial_data <= Frame[9] ; 5'd5 :o_Serial_data <= Frame[8] ; 5'd6 :o_Serial_data <= Frame[7] ; 5'd7 :o_Serial_data <= Frame[6] ; 5'd8 :o_Serial_data <= Frame[5] ; 5'd9 :o_Serial_data <= Frame[4] ; 5'd10 :o_Serial_data <= Frame[3] ; 5'd11 :o_Serial_data <= Frame[2] ; 5'd12 :o_Serial_data <= Frame[1] ; endcase end endmodule”

以下是转化后的VHDL文件：

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity Serial_output is
    port (
        i_clk         : in  std_logic;
        i_rst         : in  std_logic;
        i_T_valid     : in  std_logic;
        i_T           : in  signed(9 downto 0);
        i_Device_ID   : in  std_logic_vector(3 downto 0);
        o_Serial_data : out std_logic
    );
end entity;

architecture Behavioral of Serial_output is
    signal Frame_valid : std_logic := '0';
    signal Frame       : unsigned(13 downto 0) := (others => '0');
    signal s_Frame_valid : unsigned(2 downto 0) := (others => '0');
    signal r_bit_cnt : unsigned(4 downto 0) := (others => '0');
begin

    process (i_clk)
    begin
        if rising_edge(i_clk) then
            if i_rst = '1' then
                Frame_valid <= '0';
                Frame <= (others => '0');
            elsif i_T_valid = '1' then
                Frame_valid <= '1';
                Frame <= unsigned(i_Device_ID & i_T);
            else
                Frame_valid <= '0';
            end if;
        end if;
    end process;

    process (i_clk)
    begin
        if rising_edge(i_clk) then
            s_Frame_valid <= s_Frame_valid(1 downto 0) & Frame_valid;
        end if;
    end process;

    process (r_bit_cnt)
    begin
        case r_bit_cnt is
            when "00000" =>
                o_Serial_data <= std_logic(Frame(13));
            when "00001" =>
                o_Serial_data <= std_logic(Frame(12));
            when "00010" =>
                o_Serial_data <= std_logic(Frame(11));
            when "00011" =>
                o_Serial_data <= std_logic(Frame(10));
            when "00100" =>
                o_Serial_data <= std_logic(Frame(9));
            when "00101" =>
                o_Serial_data <= std_logic(Frame(8));
            when "00110" =>
                o_Serial_data <= std_logic(Frame(7));
            when "00111" =>
                o_Serial_data <= std_logic(Frame(6));
            when "01000" =>
                o_Serial_data <= std_logic(Frame(5));
            when "01001" =>
                o_Serial_data <= std_logic(Frame(4));
            when "01010" =>
                o_Serial_data <= std_logic(Frame(3));
            when "01011" =>
                o_Serial_data <= std_logic(Frame(2));
            when "01100" =>
                o_Serial_data <= std_logic(Frame(1));
            when others =>
                null;
        end case;
    end process;

    process (i_clk)
    begin
        if rising_edge(i_clk) then
            if i_rst = '1' then
                r_bit_cnt <= (others => '0');
            elsif s_Frame_valid(2) = '1' then
                r_bit_cnt <= (others => '0');
            elsif r_bit_cnt >= 13 then
                r_bit_cnt <= r_bit_cnt;
            else
                r_bit_cnt <= r_bit_cnt + 1;
            end if;
        end if;
    end process;

end architecture;

将下面的verilog文件改成VHDL文件“ module Time_sample( input i_clk , input i_rst , input i_ADC_clk , input [9:0] i_ADC , output o_ADC_valid , output[9:0] o_ADC ); parameter SAMPLE_TIME = 2000000000 ; parameter CLK_TIME = 20 ; parameter SIMPLE_CNT_NUM = SAMPLE_TIME/CLK_TIME ; wire [9:0] w_sync_ADC_data; wire w_empty ; sync_fifo sync_fifo_inst ( .wr_clk( i_ADC_clk ), .wr_rst( i_rst ), .rd_clk( i_clk ), .rd_rst( i_rst ), .din ( i_ADC ), .wr_en ( 1'b1 ), .rd_en ( 1'b1 ), .dout ( w_sync_ADC_data ), .full ( ), .empty ( w_empty ) ); reg [31:0] r_simple_cnt = 32'd0; always @(posedge i_clk)begin if(i_rst == 1'b1) r_simple_cnt <= 32'd0; else if(r_simple_cnt >= SIMPLE_CNT_NUM - 1'b1) r_simple_cnt <= 32'd0; else r_simple_cnt <= r_simple_cnt + 1'b1; end wire w_sample_en = (r_simple_cnt == SIMPLE_CNT_NUM - 1'b1); reg [7:0] r_ADC_data = 8'd0; reg r_ADC_valid = 1'd0 ; always @(posedge i_clk)begin if(i_rst == 1'b1)begin r_ADC_data <= 8'd0; r_ADC_valid <= 1'd0 ; end else if(w_sample_en)begin r_ADC_data <= w_sync_ADC_data; r_ADC_valid <= 1'b1; end else r_ADC_valid <= 1'b0; end assign o_ADC_valid = r_ADC_valid ; assign o_ADC = r_ADC_data ; endmodule ”

下面是将verilog文件改成VHDL文件后的代码：

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity Time_sample is
  port (
    i_clk       : in  std_logic;
    i_rst       : in  std_logic;
    i_ADC_clk   : in  std_logic;
    i_ADC       : in  std_logic_vector(9 downto 0);
    o_ADC_valid : out std_logic;
    o_ADC       : out std_logic_vector(9 downto 0)
  );
end entity;

architecture rtl of Time_sample is
  constant SAMPLE_TIME    : integer := 2000000000;
  constant CLK_TIME       : integer := 20;
  constant SIMPLE_CNT_NUM : integer := SAMPLE_TIME/CLK_TIME;
  
  signal w_sync_ADC_data : std_logic_vector(9 downto 0);
  signal w_empty        : std_logic;
  
  component sync_fifo is
    port (
      wr_clk  : in  std_logic;
      wr_rst  : in  std_logic;
      rd_clk  : in  std_logic;
      rd_rst  : in  std_logic;
      din     : in  std_logic_vector(9 downto 0);
      wr_en   : in  std_logic;
      rd_en   : in  std_logic;
      dout    : out std_logic_vector(9 downto 0);
      full    : out std_logic;
      empty   : out std_logic
    );
  end component;
  
  signal r_simple_cnt : unsigned(31 downto 0) := (others => '0');
  signal r_ADC_data   : std_logic_vector(7 downto 0) := (others => '0');
  signal r_ADC_valid  : std_logic := '0';
  
begin
  sync_fifo_inst : sync_fifo
    port map (
      wr_clk => i_ADC_clk,
      wr_rst => i_rst,
      rd_clk => i_clk,
      rd_rst => i_rst,
      din    => i_ADC,
      wr_en  => '1',
      rd_en  => '1',
      dout   => w_sync_ADC_data,
      full   => open,
      empty  => w_empty
    );
  
  process (i_clk)
  begin
    if rising_edge(i_clk) then
      if i_rst = '1' then
        r_simple_cnt <= (others => '0');
      elsif r_simple_cnt >= SIMPLE_CNT_NUM - 1 then
        r_simple_cnt <= (others => '0');
      else
        r_simple_cnt <= r_simple_cnt + 1;
      end if;
    end if;
  end process;
  
  process (i_clk)
  begin
    if rising_edge(i_clk) then
      if i_rst = '1' then
        r_ADC_data  <= (others => '0');
        r_ADC_valid <= '0';
      elsif r_simple_cnt = SIMPLE_CNT_NUM - 1 then
        r_ADC_data  <= w_sync_ADC_data(7 downto 0);
        r_ADC_valid <= '1';
      else
        r_ADC_valid <= '0';
      end if;
    end if;
  end process;
  
  o_ADC_valid <= r_ADC_valid;
  o_ADC       <= r_ADC_data & w_sync_ADC_data(8 downto 0);
  
end architecture;

在VHDL中，需要使用`library`和`use`语句来导入需要使用的库和包。此外，VHDL中没有`wire`类型，需要使用`signal`来声明信号。VHDL中的`if`语句和Verilog中的`if`语句语法有所不同，需要使用`process`语句来实现。VHDL中的赋值语句使用`<=`符号。最后，需要使用`&`符号来实现连接操作。