flashread.vhd

适用于满足I2C协议的flash读/写操作程序

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

 ENTITY flashread IS
     generic (databyteshu: integer :=4);----需要保存数据字节数
     PORT (clkin : IN std_logic;
          dataram: out std_logic_vector(7 downto 0);
          tongzhi: out std_logic:='1';
          clkout: out BIT ;
          flashread:in bit;
          datainout: inout std_logic;
           ramwrite:out bit;      ----------RAM写使能
          addrram: out integer range 0 to 9 );
 END  	flashread;                                
----------------------------------------------------------
ARCHITECTURE flashread OF flashread IS   
       SIGNAL temp_flashread :bit;
BEGIN   
------------产生相位差四分之一周期的时钟----------                                        
     PROCESS(clkin)
      VARIABLE read:bit:='0';
      VARIABLE temp1: INTEGER RANGE 0 TO 3:=0;-----产生flash周期及
                                           
      VARIABLE temp2: INTEGER :=0; -------整个计数
      VARIABLE temp4: INTEGER :=0;  -----标记写到了哪个字节
      VARIABLE temp5: INTEGER ;-------
      VARIABLE temp6: INTEGER :=0;  ---------标志字节位
      VARIABLE ramtemp: std_logic_vector(7 downto 0);----临时把要存入RAM的数据储存
     BEGIN 
---------------------------检验写信号-------------------------
         
-------------------------------------------------------------
if rising_edge(clkin) then
	temp_flashread<=flashread;
end if;
                  
       if(clkin'EVENT AND clkin='1') THEN
            temp1:=temp1+1;
            temp2:=temp2+1;
           if(flashread='1' and temp_flashread='0')then
             tongzhi<='0';
             read:='1';
             temp2:=0;
             temp1:=0;
             temp4:=0;
             temp6:=0;
                ramwrite<='1'; 
			-- temp2:=temp2+1;
			--else temp2
           end if;

             IF (temp1=1) THEN 
               clkout<= '1' and read;
                elsif (temp1=2)then
               clkout<= '1' and read;
                elsif (temp1=3)then
               clkout<='0';
                else 
                clkout<='0';
                temp1:=0;
             END IF;
           if temp2<161 then
             case temp2 is
                 when 5 => datainout<= '1';
                when 14 => datainout<= '0'; 
-------------------------------------------------
                when 16 => datainout<= '1';-----此时对应时钟低电平中点
                when 20 => datainout<= '0';
                when 24 => datainout<= '1';
                when 28 => datainout<= '0';  
----------------------------------------------------  
                when 32 => datainout<= '0'; 
                when 36 => datainout<= '0'; 
                when 40 => datainout<= '0'; 
-------------------------------------------------------------
                when 44 => datainout<= '0';   ---写命令 
--------------------------地址字节(高位)----------------------------
                when 48 => datainout<= 'Z';
                when 52 => datainout<= '0'; 
                when 56 => datainout<= '0'; 
                when 60 => datainout<= '0'; 
                when 64 => datainout<= '0'; 
                when 68 => datainout<= '0'; 
                when 72 => datainout<= '0'; 
                when 76 => datainout<= '0'; 
                when 80 => datainout<= '0'; 
--------------------------地址字节(低位)----------------------------
                when 84 => datainout<= 'Z';
                when 88 => datainout<= '0'; 
                when 92 => datainout<= '0'; 
                when 96 => datainout<= '0'; 
                when 100 => datainout<= '0'; 
                when 104 => datainout<= '0'; 
                when 108 => datainout<= '0'; 
                when 112 => datainout<= '0'; 
                when 116 => datainout<= '1'; 
----------------------------------------------------
                when 120 => datainout<= 'Z';
                when 124 => datainout<= '1';
                when 126 => datainout<= '0'; 
-------------------------------------------------
                when 128 => datainout<= '1';
                when 132 => datainout<= '0';
                when 136 => datainout<= '1';
                when 140 => datainout<= '0';  
----------------------------------------------------  
                when 144 => datainout<= '0'; 
                when 148 => datainout<= '0'; 
                when 152 => datainout<= '0'; 
-------------------------------------------------------------
                when 156 => datainout<= '1';   ---读命令 
                when 160 => datainout<= 'Z';
                        temp5:=165;    
               when others => null;  
             end case; 
          end if;
-----------------------------读取数据字节------------------------

--------------------------------------------------------------------------- 

                        if(temp2=temp5)then
                          ramtemp(temp6):=datainout;
                          temp6:=temp6+1;
                          temp5:=temp5+4;
                        end if;
                        if temp6>7 then
                           temp6:=0;
                           temp5:=166+temp4*36+36;
                           temp4:=temp4+1;

                        end if;  
                  if temp2>192  then
                         if(temp2=156+temp4*36+1+4)then
                           addrram<=temp4;-----------------第一次到此temp4=1;


                         end if;
                         if(temp2=156+temp4*36+2+4)then
                           dataram<=ramtemp;
                         end if;
------------------------------------------------------------------
                          if(temp2=156+temp4*36+4)then
                             if temp4=databyteshu+1 then
                                 temp4:=0;
                                 temp5:=166;   
                             else 
                                 datainout<='0';      ----------ACK信号
                             end if;

                         end if; 
------------------------------------------释放主线-------------------------------------------
                          if(temp2=156+temp4*36+8)then
 
                                 datainout<='Z';    --- 释放主线
                         end if; 


                   end if;
         if  temp2=156+databyteshu*36+4 then
                 datainout<='1';        ---------------------最后一字节不应答
          end if; 

------------------------停止信号产生--------------

         if  temp2=156+databyteshu*36+8 then
                 datainout<='0';
          end if; 
         if  temp2=156+databyteshu*36+10 then
             datainout<='1';
               ramwrite<='0';
             tongzhi<='1';
         end if; 
----------------------------读结束后释放总线关闭时钟--------------
         if  temp2=156+databyteshu*36+12 then
             datainout<='Z';
             tongzhi<='0';
               read:='0';-----------------此后时钟始终为零注意复用
         end if; 
----------------------------------------------------------------    
      END IF;
           
     END PROCESS;

END flashread;