串口RS485实现（TOF FPGA TDC中使用）

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
use std.textio.all;

entity RS485serialInterface is
port(
    Clk : in std_logic;
     reset : in std_logic;
--    Rclk : in std_logic;
--    Tclk : in std_logic;
    RS485RO : in std_logic;
    receiverData : out std_logic_vector(7 downto 0);
    RS485DI : out std_logic;
    transferData : in std_logic_vector(7 downto 0);
    busy : out std_logic;
    CTTPfifoRdreq : in std_logic
    );
    end RS485serialInterface;
    
architecture Art_RS485serialInterface of RS485serialInterface is
    
signal receiverReg : std_logic_vector(7 downto 0);
signal transmitterReg : std_logic_vector(9 downto 0);
signal counter : std_logic_vector(7 downto 0);
signal cont : std_logic_vector(7 downto 0);
type State1 is (WaitStartBit,GetStartBit,GetDataBit0,GetDataBit1,GetDataBit2,GetDataBit3,GetDataBit4,GetDataBit5,GetDataBit6,GetDataBit7,GetStopBit,GetData);
signal receiverState : State1;
type State2 is (Idle,transStartBit,transDataBit0,transDataBit1,transDataBit2,transDataBit3,transDataBit4,transDataBit5,transDataBit6,transDataBit7,transStopBit);
signal transferState : State2;

begin

-----------------RS485 receiver-----------
process(Clk,reset)
begin
if reset='1' then
   receiverReg<=(others=>'0');
   receiverData<=(others=>'0');
   counter<=(others=>'0');
   receiverState<=WaitStartBit;
elsif Clk'event and Clk='1' then
   case receiverState is
   when WaitStartBit=>
        receiverReg<=(others=>'0');
        if RS485RO='0' then
           counter<=counter+1;
           receiverState<=GetStartBit;
        else
           counter<=(others=>'0');
           receiverState<=WaitStartBit;
        end if;
   when GetStartBit=>
        if counter="110010" then
           counter<=(others=>'0');
           receiverState<=GetDataBit0;
        elsif RS485RO='0' then
           counter<=counter+1;
           receiverState<=GetStartBit;
        else
           receiverState<=WaitStartBit;
        end if;
   when GetDataBit0=>
        if counter="1100100" then
           receiverReg(0)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit1;
        else
           counter<=counter+1;
           receiverState<=GetDataBit0;
        end if;
   when GetDataBit1=>
        if counter="1100100" then
           receiverReg(1)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit2;
        else
           counter<=counter+1;
           receiverState<=GetDataBit1;
        end if;
   when GetDataBit2=>
        if counter="1100100" then
           receiverReg(2)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit3;
        else
           counter<=counter+1;
           receiverState<=GetDataBit2;
        end if;
   when GetDataBit3=>
        if counter="1100100" then
           receiverReg(3)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit4;
        else
           counter<=counter+1;
           receiverState<=GetDataBit3;
        end if;
   when GetDataBit4=>
        if counter="1100100" then
           receiverReg(4)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit5;
        else
           counter<=counter+1;
           receiverState<=GetDataBit4;
        end if;
   when GetDataBit5=>
        if counter="1100100" then
           receiverReg(5)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit6;
        else
           counter<=counter+1;
           receiverState<=GetDataBit5;
        end if;
   when GetDataBit6=>
        if counter="1100100" then
           receiverReg(6)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetDataBit7;
        else
           counter<=counter+1;
           receiverState<=GetDataBit6;
        end if;
   when GetDataBit7=>
        if counter="1100100" then
           receiverReg(7)<=RS485RO;
           counter<=(others=>'0');
           receiverState<=GetStopBit;
        else
           counter<=counter+1;
           receiverState<=GetDataBit7;
        end if;
   when GetStopBit=>
        if counter="1100100" then
           counter<=(others=>'0');
           receiverState<=GetData;
        else
           counter<=counter+1;
           receiverState<=GetStopBit;
        end if;
   when GetData=>
        receiverData<=receiverReg;
        receiverState<=WaitStartBit;
   when others=>
        receiverReg<=(others=>'0');
        receiverData<=(others=>'0');
        counter<=(others=>'0');
        receiverState<=WaitStartBit;
   end case;
end if;
end process;


--------------RS485 transfer---------
process(Clk,reset)
begin
if reset='1' then
   RS485DI<='1';
   busy<='0';
    cont<=(others=>'0');
   transferState<=Idle;
elsif Clk'event and Clk='1' then
   case transferState is
   when Idle=>
        if CTTPfifoRdreq='1' then
           busy<='1';
           transferState<=transStartBit;
        else
           busy<='0';
           transferState<=Idle;
        end if;
   when transStartBit=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<='0';
           cont<=(others=>'0');              
           transferState<=transDataBit0;
          else
             cont<=cont+1;
              busy<='1';
              RS485DI<='0';          
           transferState<=transStartBit;
          end if;
   when transDataBit0=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(0);
           cont<=(others=>'0');              
           transferState<=transDataBit1;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(0);
           transferState<=transDataBit0;
          end if;
   when transDataBit1=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(1);
           cont<=(others=>'0');              
           transferState<=transDataBit2;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(1);
           transferState<=transDataBit1;
          end if;
   when transDataBit2=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(2);
           cont<=(others=>'0');              
           transferState<=transDataBit3;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(2);
           transferState<=transDataBit2;
          end if;
   when transDataBit3=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(3);
           cont<=(others=>'0');              
           transferState<=transDataBit4;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(3);
           transferState<=transDataBit3;
          end if;
   when transDataBit4=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(4);
           cont<=(others=>'0');              
           transferState<=transDataBit5;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(4);
           transferState<=transDataBit4;
          end if;
   when transDataBit5=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(5);
           cont<=(others=>'0');              
           transferState<=transDataBit6;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(5);
           transferState<=transDataBit5;
          end if;
   when transDataBit6=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(6);
           cont<=(others=>'0');              
           transferState<=transDataBit7;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(6);
           transferState<=transDataBit6;
          end if;
   when transDataBit7=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<=transferData(7);
           cont<=(others=>'0');              
           transferState<=transStopBit;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<=transferData(7);
           transferState<=transDataBit7;
          end if;
   when transStopBit=>
        if(cont="1100100")then
             busy<='1';
           RS485DI<='1';
           cont<=(others=>'0');              
           transferState<=Idle;
          else
             cont<=cont+1;
             busy<='1';
           RS485DI<='1';
           transferState<=transStopBit;
          end if;
   when others=>
        busy<='0';
        RS485DI<='0';
        transferState<=Idle;
   end case;
 end if;
end process;  
        
end Art_RS485serialInterface;