VHDL RS485 通信代码示例 - 实现数据传输与接收

{"title":"VHDL RS485 通信代码示例 - 实现数据传输与接收", "description":"本文提供了一个基于 VHDL 的 RS485 通信代码示例，展示了如何使用 VHDL 实现数据发送和接收功能。代码包含发送使能延时、接收使能延时等，并解释了每个模块的作用。", "keywords":"VHDL, RS485, 通信, 代码示例, 数据传输, 数据接收, 发送使能, 接收使能, 延时, 波特率, 时钟频率", "content":"以下是一个基于 VHDL 的 485 通信代码示例：\n\nvhdl\nlibrary IEEE;\nuse IEEE.std_logic_1164.all;\nuse IEEE.numeric_std.all;\n\nentity RS485_Communication is\n generic (\n DATA_WIDTH : natural := 8; -- 数据位宽\n BAUD_RATE : natural := 9600; -- 波特率\n CLK_FREQ : natural := 50000000; -- 时钟频率\n TX_EN_DELAY : natural := 10; -- 发送使能延时\n RX_EN_DELAY : natural := 10; -- 接收使能延时\n HALF_BIT_DELAY : natural := CLK_FREQ / (2 * BAUD_RATE) -- 半个位延时\n );\n port (\n clk : in std_logic; -- 输入时钟\n reset : in std_logic; -- 复位信号\n tx_data : in std_logic_vector(DATA_WIDTH - 1 downto 0); -- 发送数据\n rx_data : out std_logic_vector(DATA_WIDTH - 1 downto 0); -- 接收数据\n tx_en : out std_logic; -- 发送使能信号\n rx_en : out std_logic -- 接收使能信号\n );\nend RS485_Communication;\n\narchitecture Behavioral of RS485_Communication is\n signal tx_count : natural range 0 to DATA_WIDTH + 1;\n signal rx_count : natural range 0 to DATA_WIDTH + 1;\n signal tx_bit : std_logic;\n signal rx_bit : std_logic;\n signal tx_done : std_logic;\n signal rx_done : std_logic;\n \nbegin\n\n -- 发送数据逻辑\n process(clk, reset)\n begin\n if reset = '1' then\n tx_en <= '0';\n tx_count <= 0;\n tx_bit <= '0';\n tx_done <= '0';\n elsif rising_edge(clk) then\n if tx_done = '0' then\n if tx_count = 0 then\n tx_en <= '1'; -- 启动发送使能\n tx_bit <= '0';\n elsif tx_count <= DATA_WIDTH then\n tx_en <= '1'; -- 启动发送使能\n tx_bit <= tx_data(tx_count - 1);\n elsif tx_count = DATA_WIDTH + 1 then\n tx_en <= '1'; -- 启动发送使能\n tx_bit <= '1';\n elsif tx_count = DATA_WIDTH + 2 then\n tx_en <= '0'; -- 停止发送使能\n tx_done <= '1';\n end if;\n tx_count <= tx_count + 1;\n else\n tx_en <= '0';\n end if;\n end if;\n end process;\n\n -- 接收数据逻辑\n process(clk, reset)\n begin\n if reset = '1' then\n rx_en <= '0';\n rx_count <= 0;\n rx_bit <= '0';\n rx_done <= '0';\n rx_data <= (others => '0');\n elsif rising_edge(clk) then\n if rx_done = '0' then\n if rx_count = 0 then\n rx_en <= '1'; -- 启动接收使能\n elsif rx_count = DATA_WIDTH + 1 then\n rx_en <= '0'; -- 停止接收使能\n rx_done <= '1';\n end if;\n rx_count <= rx_count + 1;\n else\n rx_en <= '0';\n rx_data <= rx_data(DATA_WIDTH - 2 downto 0) & rx_bit; -- 存储接收到的数据\n end if;\n end if;\n end process;\n\n -- 发送使能延时\n process(clk)\n begin\n if rising_edge(clk) then\n if tx_en = '1' then\n wait for TX_EN_DELAY * HALF_BIT_DELAY;\n tx_en <= '0';\n end if;\n end if;\n end process;\n\n -- 接收使能延时\n process(clk)\n begin\n if rising_edge(clk) then\n if rx_en = '1' then\n wait for RX_EN_DELAY * HALF_BIT_DELAY;\n rx_en <= '0';\n end if;\n end if;\n end process;\n\n -- 发送数据\n process(clk)\n begin\n if rising_edge(clk) then\n if tx_en = '1' then\n tx_done <= '0';\n end if;\n end if;\n end process;\n\n -- 接收数据\n process(clk)\n begin\n if rising_edge(clk) then\n if rx_en = '1' then\n rx_done <= '0';\n rx_bit <= '0';\n elsif rx_en = '0' and rx_done = '0' then\n rx_bit <= not rx_bit;\n end if;\n end if;\n end process;\n\nend Behavioral;\n\n\n