vhdl实现uart
时间: 2023-08-06 08:05:54 浏览: 57
下面是一个简单的 VHDL 代码实现 UART:
```
entity UART is
Port ( CLK : in std_logic;
RST : in std_logic;
TX : out std_logic;
RX : in std_logic);
end UART;
architecture Behavioral of UART is
signal TX_shift_reg : std_logic_vector(9 downto 0);
signal TX_busy : std_logic := '0';
signal TX_data : std_logic_vector(7 downto 0);
signal TX_counter : integer range 0 to 11 := 0;
signal RX_shift_reg : std_logic_vector(9 downto 0);
signal RX_busy : std_logic := '0';
signal RX_data : std_logic_vector(7 downto 0);
signal RX_counter : integer range 0 to 11 := 0;
constant BAUD_RATE : integer := 9600;
constant CLK_FREQ : integer := 50000000; -- 50 MHz clock
begin
UART_TX : process(CLK, RST)
begin
if(RST = '1') then
TX_shift_reg <= (others => '1');
TX_busy <= '0';
TX_counter <= 0;
elsif(CLK'event and CLK = '1') then
if(TX_busy = '1') then
TX_counter <= TX_counter + 1;
if(TX_counter = 11) then
TX_shift_reg <= TX_shift_reg(TX_shift_reg'high - 1 downto 0) & '1';
TX_busy <= '0';
TX_counter <= 0;
end if;
else
if(TX_shift_reg(TX_shift_reg'high) = '0') then
TX <= '0';
TX_busy <= '1';
TX_counter <= 0;
else
TX <= '1';
end if;
end if;
end if;
end process UART_TX;
UART_RX : process(CLK, RST)
begin
if(RST = '1') then
RX_shift_reg <= (others => '1');
RX_busy <= '0';
RX_counter <= 0;
elsif(CLK'event and CLK = '1') then
if(RX_busy = '1') then
RX_counter <= RX_counter + 1;
if(RX_counter = 11) then
RX_data <= RX_shift_reg(RX_shift_reg'high - 2 downto RX_shift_reg'low);
RX_shift_reg <= (others => '1');
RX_busy <= '0';
RX_counter <= 0;
end if;
else
RX_shift_reg <= RX_shift_reg(RX_shift_reg'high - 1 downto 0) & RX;
if(RX_shift_reg(RX_shift_reg'high - 1 downto RX_shift_reg'high - 10) = "0101010101") then
RX_busy <= '1';
RX_counter <= 0;
end if;
end if;
end if;
end process UART_RX;
-- Baud rate generator
UART_BAUD : process(CLK, RST)
begin
if(RST = '1') then
TX_shift_reg(TX_shift_reg'high) <= '1';
elsif(CLK'event and CLK = '1') then
TX_shift_reg(TX_shift_reg'high) <= not TX_shift_reg(TX_shift_reg'high);
end if;
end process UART_BAUD;
end Behavioral;
```
这个实现包括了一个简单的波特率生成器和 TX 和 RX 的状态机。该实现使用9600波特率,50 MHz时钟频率和8个数据位。