mcuconnect.vhd

用VHDL来提高MCU的连接速度。对MCU有兴趣的朋友

library IEEE;
use IEEE.STD_LOGIC_1164.all;

entity mcuconnect is
	 port(
	 	   --reset: in std_logic;
	       ALE  : in STD_LOGIC;                                --ale signal                            	                                  
		   WR   : in STD_LOGIC;                                --write signal
	       RD   : in STD_LOGIC;                                -- read signal
		   RST  : in STD_LOGIC;                                -- master reset signal
		   DTA  : in STD_LOGIC;                                --data acknowledge signal 
		   A    : in STD_LOGIC_VECTOR(8 to 15);               --high address input signal
		   RorW : out STD_LOGIC;                               -- read and write signal
		   AB   : out STD_LOGIC_VECTOR(0 to 15);              --address out signal
		   D    : inout STD_LOGIC_VECTOR(0 to 7);             --inout data and CPU connect signal
		   CS   : out STD_LOGIC;                               -- slow coin select signal
		   DO   : inout STD_LOGIC_VECTOR(0 to 7)              --inout  data and other slow coin signal
	     );
end mcuconnect;

--}} End of automatically maintained section 

architecture mcuconnect of mcuconnect is	

signal ABird    : std_logic_vector(0 to 7);
signal tempR    : std_logic;
signal tempW    : std_logic;
signal CStemp   : std_logic; 
signal CKtemp   : std_logic_vector(1 to 3);
signal PR       : std_logic;
signal LatchALE : std_logic; 
signal CSmiddle : std_logic; 
signal Dtemp    : std_logic_vector(0 to 7);
signal DOtemp   : std_logic_vector(0 to 7);

begin
	
    CStemp <= not(A(15) and A(14) and not A(13) and not A(12));
	CKtemp(1) <= not((WR and RD) or CStemp);	
	CKtemp(2) <= not(CStemp or RD);
	CKtemp(3) <= not(CStemp or WR); 
	--PR <= not(not DTA or RST); -- DTA high effective
	PR <= DTA and not RST;  -- DTA low effective
	
	-- enter your statements here -- 
	process(ALE)
	begin
		if(ALE'EVENT and ALE = '0')	 then 
			ABird <= D;
		end if;
	end process;
	
	process(CKtemp(3))
	begin
		if(CKtemp(3)'EVENT and CKtemp(3)='1') then
			Dtemp <= D;
		end if;
	end process;
	
	process(PR,CKtemp)
	begin
		if(PR = '0') then	   --DTA low effective
			CSmiddle <= '1';
			tempR <= '1';
			tempW <= '1'; 
		else
			if(CKtemp(1)'EVENT and CKtemp(1)='1') then
				CSmiddle <= '0';
			end if;
			
			if(CKtemp(2)'EVENTt and CKtemp(2)='1') then
				tempR <= '0'; 
			end if;
			
			if(CKtemp(3)'EVENT and CKtemp(3)='1') then
				tempW <= '0';
			end if;			
		end if;	
    	CS<= CSmiddle;
        LatchALE <= CSmiddle and ALE;
	end process;
	
	process(LatchALE)	
	begin
		if(LatchALE'EVENT and LatchALE='0') then
			AB(0 to 7) <= D;
			AB(8 to 15) <= A;
		end if;			
	end process; 
	
    process(CKtemp(2))
	begin
		if(CKtemp(2)='1') then
			D <= DOtemp; 
		else
			D <= "ZZZZZZZZ";
		end if;
    end process;

	process(tempR) 
	begin
		if(tempR'EVENT and tempR='1') then
			DOtemp <= DO;	
		end if;  			   
	end process;
	
	process(tempW)
	begin
		if(tempW='0') then	
			DO <= Dtemp;
		else
			DO <= "ZZZZZZZZ";
		end if;
	end process; 

    RorW <= tempW or not tempR;	 
	
end mcuconnect;