portcout.vhd

8255的vhdl 程序

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

ENTITY portcout IS
   PORT(
      RESET         : IN std_logic;
      CLK           : IN std_logic;
      DIN           : IN std_logic_vector (7 DOWNTO 0);
      PCIN          : IN std_logic_vector (7 DOWNTO 0);
      ControlReg    : IN std_logic_vector (7 DOWNTO 0);
      PortARead     : IN std_logic;
      PortBRead     : IN std_logic;
      PortAWrite    : IN std_logic;
      PortBWrite    : IN std_logic;
      PortCOverride : IN std_logic;
      PortCOutLd    : IN std_logic_vector (7 DOWNTO 0);
      PortCStatus   : OUT std_logic_vector (7 DOWNTO 0);
      PCOUT         : OUT std_logic_vector (7 DOWNTO 0)
   );

END portcout;


ARCHITECTURE rtl OF portcout IS

   SIGNAL    PortCOutRegD    : std_logic_vector(7 DOWNTO 0);
   SIGNAL    PortCOutRegQ    : std_logic_vector(7 DOWNTO 0);
   SIGNAL    ModeA           : std_logic_vector (1 DOWNTO 0);
   SIGNAL    ModeB           : std_logic;
   SIGNAL    PortA_IO        : std_logic;
   SIGNAL    PortB_IO        : std_logic;
   SIGNAL	 RisePortAWriteQ : std_logic;
   SIGNAL	 RisePortBWriteQ : std_logic;
   SIGNAL	 RisePortAReadQ  : std_logic;
   SIGNAL	 RisePortBReadQ  : std_logic;
   SIGNAL	 RisePCIN6Q      : std_logic;
   SIGNAL	 RisePCIN4Q      : std_logic;
   SIGNAL	 RisePCIN2Q      : std_logic;
   SIGNAL	 RisePortAWrite  : std_logic;
   SIGNAL	 RisePortBWrite  : std_logic;
   SIGNAL	 RisePortARead   : std_logic;
   SIGNAL	 RisePortBRead   : std_logic;
   SIGNAL	 RisePCIN6       : std_logic;
   SIGNAL    RisePCIN4       : std_logic;
   SIGNAL    RisePCIN2       : std_logic;


   BEGIN

	  PCOUT       <= PortCOutRegQ;
      ModeA       <= ControlReg (6 DOWNTO 5);
      ModeB       <= ControlReg (2);
      PortA_IO    <= ControlReg (4);
      PortB_IO    <= ControlReg (1);

	  PortCStatusProc: PROCESS ( ModeA, ModeB, PortA_IO, PCIN, PortCOutRegQ )
	     BEGIN
		    PortCStatus(7) <= PCIN(7);

            IF (ModeA = "01" AND PortA_IO = '0') THEN	   -- Mode 1
		       PortCStatus(6) <= PortCoutRegQ(6);
			ELSIF (ModeA(1) = '1') THEN   				   -- Mode 2
		       PortCStatus(6) <= PortCoutRegQ(6);
			ELSE
		       PortCStatus(6) <= PCIN(6);
			END IF;

		    PortCStatus(5) <= PCIN(5);

            IF (ModeA = "01" AND PortA_IO = '1') THEN	   -- Mode 1
		       PortCStatus(4) <= PortCoutRegQ(4);
			ELSIF (ModeA(1) = '1') THEN   				   -- Mode 2
		       PortCStatus(4) <= PortCoutRegQ(4);
			ELSE
		       PortCStatus(4) <= PCIN(4);
			END IF;

		    PortCStatus(3) <= PCIN(3);

            IF (ModeB = '1') THEN	                       -- Mode 1
		       PortCStatus(2) <= PortCoutRegQ(2);
			ELSE
		       PortCStatus(2) <= PCIN(2);
			END IF;

		    PortCStatus(1) <= PCIN(1);
		    PortCStatus(0) <= PCIN(0);
	     END PROCESS;


      PortCDataProc: PROCESS ( ModeA, PortA_IO, PortB_IO, ModeB, PortCOverride,
                               PortAWrite, PortBWrite, PortARead, PortBRead,
                               RisePortAWrite, RisePortBWrite, RisePortARead, RisePortBRead,
                               PortCOutLd, PortCOutRegQ, DIN,
                               PCIN, RisePCIN2, RisePCIN4, RisePCIN6 )

         BEGIN

            IF (ModeB = '0') THEN				                            -- Mode 0
			   IF (PortCOutLd (0) = '0') THEN								-- Load from bus and bit set/reset
                  PortCOutRegD (0)  <= DIN(0);
			   ELSE
                  PortCOutRegD (0)  <= PortCOutRegQ (0);
			   END IF;
			ELSIF (ModeB = '1') THEN								        -- Mode 1
               IF ( PortCOutLd (0) = '0' AND PortCOverride = '1')  THEN     -- Load for the set/reset command
                  PortCOutRegD (0)  <= DIN(0);								-- Mode 1 Output
			   ELSIF (PortB_IO = '0') THEN
			      IF (PortBWrite = '0') THEN								-- Reset INTRB on write strobe
                     PortCOutRegD (0)  <=  '0';
				  ELSIF (PortBWrite = '1' AND RisePCIN2 = '1' 				-- Set INTRB on rising edge of ACKB
				         AND PortCOutRegQ (1) = '1') THEN
                     PortCOutRegD (0)  <= PortCOutRegQ (2);
				  ELSE
                     PortCOutRegD (0)  <= PortCOutRegQ (0);
				  END IF;
			   ELSE															-- Mode 1 Input
			      IF (PortBRead = '0' AND PortCOutRegQ(1) = '1') THEN		-- Reset INTRB on read strobe
                     PortCOutRegD (0)  <=  '0';
				  ELSIF (RisePCIN2 = '1' AND PortCOutRegQ (1) = '1') THEN	-- Set INTRB on rising edge of STBB
                     PortCOutRegD (0)  <= PortCOutRegQ (2);
				  ELSE
                     PortCOutRegD (0)  <= PortCOutRegQ (0);
				  END IF;
               END IF;
			ELSE
                  PortCOutRegD (0)  <= PortCOutRegQ (0);
			END IF;


            IF (ModeB = '0') THEN				                           -- Mode 0
			   IF (PortCOutLd (1) = '0') THEN
                  IF ( PortCOverride = '1')  THEN                     	   
                     PortCOutRegD (1)  <= DIN(0);						   -- Load from bit set/reset
			      ELSE
                     PortCOutRegD (1)  <= DIN(1);						   -- Load from bus
                  END IF;
			   ELSE
                  PortCOutRegD (1)  <= PortCOutRegQ (1);
			   END IF;
			ELSIF (ModeB = '1') THEN								       -- Mode 1
               IF ( PortCOutLd (1) = '0' AND PortCOverride = '1')  THEN    -- Load from bit set/reset
                  PortCOutRegD (1)  <= DIN(0);
			   ELSIF (PortB_IO = '0') THEN								   -- Mode 1 Output
			      IF (RisePortBWrite = '1') THEN						   -- Reset OBFB on rising edge of write strobe
                     PortCOutRegD (1)  <=  '0';
				  ELSIF (PCIN(2) = '0') THEN							   -- Set OBFB when ACKB goes low
                     PortCOutRegD (1)  <= '1';
				  ELSE
                     PortCOutRegD (1)  <= PortCOutRegQ (1);
				  END IF;
			   ELSE														  -- Mode 1 Input
			      IF (RisePortBRead = '1' AND PortCOutRegQ(0) = '0') THEN -- Reset IBFB on rising edge of read strobe
                     PortCOutRegD (1)  <=  '0';
				  ELSIF (PCIN(2) = '0') THEN							  -- Set IBFB when STBB goes low
                     PortCOutRegD (1)  <= '1';
				  ELSE
                     PortCOutRegD (1)  <= PortCOutRegQ (1);
				  END IF;
               END IF;
			ELSE
                  PortCOutRegD (1)  <= PortCOutRegQ (1);
			END IF;


            IF (PortCOutLd (2) = '0') THEN				                  -- All Modes
               IF ( PortCOverride = '1')  THEN                     
                  PortCOutRegD (2)  <= DIN(0);							  -- Load INTEB from bit set/reset
			   ELSE
                  PortCOutRegD (2)  <= DIN(2);							  -- Load INTEB from bus
               END IF;
			ELSE
                  PortCOutRegD (2)  <= PortCOutRegQ (2);
			END IF;



            IF (ModeA = "00") THEN										  -- Mode 0

			   IF (PortCOutLd (3) = '0') THEN
                  IF ( PortCOverride = '1')  THEN
                     PortCOutRegD (3)  <= DIN(0);                         -- Load from bit set/reset
			      ELSE
                     PortCOutRegD (3)  <= DIN(3);						  -- Load from bus
                  END IF;
			   ELSE
                  PortCOutRegD (3)  <= PortCOutRegQ (3);
			   END IF;
			ELSIF (ModeA = "01") THEN								      -- Mode 1
               IF ( PortCOutLd (3) = '0' AND PortCOverride = '1')  THEN
                  PortCOutRegD (3)  <= DIN(0);							  -- Load from bit set/reset
			   ELSIF (PortA_IO = '0') THEN								  -- Mode 1 Output
			      IF (PortAWrite = '0') THEN							  
                     PortCOutRegD (3)  <=  '0';							  -- Reset INTRA on write strobe
				  ELSIF (PortAWrite = '1' AND RisePCIN6 = '1' 			  -- Set INTRA on rising edge of ACKA
				         AND PortCOutRegQ (7) = '1') THEN
                     PortCOutRegD (3)  <= PortCOutRegQ (6);
				  ELSE
                     PortCOutRegD (3)  <= PortCOutRegQ (3);
				  END IF;
			   ELSE														  -- Mode 1 Input
			      IF (PortARead = '0' AND PortCOutRegQ(5) = '1') THEN