i2c_tshift.vhd

这是一个I2C串行数据通信协议以VHDL硬件描述语言实现的IP核

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity i2c_tshift is
port(
     fi2c:in std_logic;
     tx:in std_logic_vector(7 downto 0);
     shift_en1,shift_i,shift_temp:in std_logic;
     shift_i1,shift_en,sda:out std_logic
    );
end i2c_tshift;
architecture behav of i2c_tshift is
signal int:std_logic_vector(3 downto 0);
signal txtag,shift_again:std_logic;
signal txreg:std_logic_vector(7 downto 0);
begin
  shift_again<=shift_en1 xor shift_temp;

b:process(fi2c)
begin
if(shift_again='1') then
 txreg<=tx;
elsif rising_edge(fi2c) then
 if(shift_en1='1' ) then
  txreg<=txreg(6 downto 0)&txtag;
  txtag<='0';
  if(int="1000") then
    shift_en<='0';
    shift_i1<='1';
    sda<='0';
  else
    sda<=txreg(7);
    shift_en<='1';
  end if;
 else
 
  shift_i1<='0';
 end if;
end if;
end process b;
a:process(shift_i,shift_again)
begin
 if(shift_again='1') then
  int<="0000";
 elsif rising_edge(shift_i) then
  int<=int+1;
  if(int="1000") then
   int<="0000";
  end if;
 end if;
end process a;
end behav;