send_word.vhd

UART的完整发送程序

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--File name : Send_Word.vhd
--Function : 字符发送控制器，发送"I love you!"
--Interface : 	clk    -为时钟信号，波特率为clk的1/4
--        		din    -发送完毕空信号输入
--        		wr     -写使能信号
--        		dout   -要发送的数据，8bit
--Author : wanyou
--Date : 2008-03-24
----------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;

entity Send_Word is
port(
	clk : in std_logic;
	din : in std_logic;
	wr  : in std_logic:='1';
	dout : out std_logic_vector(7 downto 0)
	);
end Send_Word;

architecture behave of Send_Word is
type states is(s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,
				s11,s12,s13,s14,s15,s16);
signal state : states:=s0;
begin
	process(clk)
	begin
		if rising_edge(clk) then
			case state is
				when s0 =>
					dout <= "00000000";
					if din = '1' then
						state <= s1;
						wr <= '0';
					else
						state <= s0;
						wr <= '1';
					end if;
				when s1 =>
					dout <= "00000000";
					if din = '1' then
						state <= s2;
						wr <= '0';
					else
						state <= s1;
						wr <= '1';
					end if;
				when s1=>--wr<='0';          
                    qout<="00000000";
                    if tdempty='1' then
                       state<=s2;
                       wr<='0';
                    else
                       state<=s1;
                       wr<='1';
                    end if;
				when s2=>--wr<='0';             --发送‘I’
                    qout<="01001001";
                    if tdempty='1' then
                       state<=s3;
                       wr<='0';
                    else
                       state<=s2;
                       wr<='1';
                    end if;
				when s3=>--wr<='1';             --发送空格
                    qout<="00100000";
                    if tdempty='1' then
                       state<=s4;
                       wr<='0';
                    else
                       state<=s3;
                       wr<='1';
                    end if;
				when s4=>--wr<='1';             --发送‘l’
                    qout<="01101100";
                    if tdempty='1' then
                       state<=s5;
                       wr<='0';
                    else
                       state<=s4;
                       wr<='1';
                    end if;
				when s5=>--wr<='1';             --发送‘o’
                    qout<="01101111";
                    if tdempty='1' then
                       state<=s6;
                       wr<='0';
                    else
                       state<=s5;
                       wr<='1';
                    end if;
				when s6=>--wr<='1';             --发送‘v’
                    qout<="01110110";
                    if tdempty='1' then
                       state<=s7;
                       wr<='0';
                    else
                       state<=s6;
                       wr<='1';
                    end if;
				when s7=>--wr<='1';             --发送‘e’
                    qout<="01100101";
                    if tdempty='1' then
                       state<=s8;
                       wr<='0';
                    else
                       state<=s7;
                       wr<='1';
                    end if;
				when s8=>--wr<='1';             --发送空格
                    qout<="00100000";
                    if tdempty='1' then
                       state<=s9;
                       wr<='0';
                    else
                       state<=s8;
                       wr<='1';
                    end if;
				when s9=>--wr<='1';             --发送‘y’
                    qout<="01111001";
                    if tdempty='1' then
                       state<=s10;
                       wr<='0';
                    else
                       state<=s9;
                       wr<='1';
                    end if;
				when s10=>--wr<='1';             --发送‘o’
                    qout<="01101111";
                    if tdempty='1' then
                       state<=s11;
                       wr<='0';
                    else
                       state<=s10;
                       wr<='1';
                    end if;
				when s11=>--wr<='1';            --发送‘u’
                    qout<="01110101";
                    if tdempty='1' then
                       state<=s12;
                       wr<='0';
                    else
                       state<=s11;
                       wr<='1';
                    end if;
				when s12=>--wr<='1';            --发送‘！’
                    qout<="00100001";
                    if tdempty='1' then
                       state<=s13;
                       wr<='0';
                    else
                       state<=s12;
                       wr<='1';
                    end if;
				when s13=>--wr<='1';            --发送空格
                    qout<="00100000";
                    if tdempty='1' then
                       state<=s2;
                       wr<='0';
                    else
                       state<=s13;
                       wr<='1';
                    end if;
				when others=>
						state<=s1;
                        wr<='0';
                        qout<="00000000";
         end case;                     
    end if;
  end process;
end behave;