dec.vhd.bak

vhdl code for a 16 bit decoder design

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL; 

ENTITY rc5_dnc IS
    PORT
    (
	clk,clr	: IN STD_LOGIC; 
	din	: IN STD_LOGIC_VECTOR(63 DOWNTO 0); 
	dout	: OUT STD_LOGIC_VECTOR(63 DOWNTO 0); 
	di_vld: IN STD_LOGIC;
   do_rdy: OUT STD_LOGIC 

     );
END rc5_dnc;


ARCHITECTURE do OF rc5_dnc IS
    SIGNAL i_cnt	: STD_LOGIC_VECTOR(3 DOWNTO 0); -- round counter
    SIGNAL a_rot	: STD_LOGIC_VECTOR(31 DOWNTO 0);-- right rotate by b
    SIGNAL a	: STD_LOGIC_VECTOR(31 DOWNTO 0);-- the input a
    SIGNAL a_reg	: STD_LOGIC_VECTOR(31 DOWNTO 0); -- register a
    SIGNAL a_pre	: STD_LOGIC_VECTOR(31 DOWNTO 0); -- register a pre
    SIGNAL b_rot	: STD_LOGIC_VECTOR(31 DOWNTO 0);-- right rotate by a
    SIGNAL b	: STD_LOGIC_VECTOR(31 DOWNTO 0);--the input b
    SIGNAL b_reg	: STD_LOGIC_VECTOR(31 DOWNTO 0); -- register a
    SIGNAL b_pre	: STD_LOGIC_VECTOR(31 DOWNTO 0); -- register b pre
    SIGNAL b_temp	: STD_LOGIC_VECTOR(31 DOWNTO 0);
    SIGNAL a_temp	: STD_LOGIC_VECTOR(31 DOWNTO 0);

    TYPE rom IS ARRAY (0 TO 25) OF STD_LOGIC_VECTOR(31 DOWNTO 0);
   
    CONSTANT skey : rom:=rom'(X"9BBBD8C8", X"1A37F7FB", X"46F8E8C5",X"460C6085",X"70F83B8A",X"284B8303",X"513E1454",X"F621ED22",X"3125065D",X"11A83A5D",X"D427686B",X"713AD82D",X"4B792F99",X"2799A4DD",X"A7901C49",X"DEDE871A",X"36C03196",X"A7EFC249",X"61A78BB8",X"3B0A1D2B",X"4DBFCA76",X"AE162167",X"30D76B0A",X"43192304",X"F6CC1431",X"65046380");
                    -- assign the values for S[0]~ S[25] although we only need to use s[2]~S[12]

    --states
    TYPE  StateType IS (ST_IDLE, ST_PRE_ROUND,  ST_ROUND_OP,  ST_READY   );
    SIGNAL  state   :   StateType;

BEGIN
    -- B= ((B-S[2*i]>>>A)) XOR A

    b_temp<= b_reg-skey(CONV_INTEGER(i_cnt & '1'));
    WITH a_reg(4 DOWNTO 0) SELECT
    b_rot<=b_temp(0) & b_temp(31 DOWNTO 1) WHEN "00001",
           b_temp(1 DOWNTO 0) & b_temp(31 DOWNTO 2) WHEN "00010",
	        b_temp(2 DOWNTO 0) & b_temp(31 DOWNTO 3) WHEN "00011",
	        b_temp(3 DOWNTO 0) & b_temp(31 DOWNTO 4) WHEN "00100",
	        b_temp(4 DOWNTO 0) & b_temp(31 DOWNTO 5) WHEN "00101",
	        b_temp(5 DOWNTO 0) & b_temp(31 DOWNTO 6) WHEN "00110",
          	b_temp(6 DOWNTO 0) & b_temp(31 DOWNTO 7) WHEN "00111",
          	b_temp(7 DOWNTO 0) & b_temp(31 DOWNTO 8) WHEN "01000",
	        b_temp(8 DOWNTO 0) & b_temp(31 DOWNTO 9) WHEN "01001",
	        b_temp(9 DOWNTO 0) & b_temp(31 DOWNTO 10) WHEN "01010",
	        b_temp(10 DOWNTO 0) & b_temp(31 DOWNTO 11) WHEN "01011",
           b_temp(11 DOWNTO 0) & b_temp(31 DOWNTO 12) WHEN "01100",
	        b_temp(12 DOWNTO 0) & b_temp(31 DOWNTO 13) WHEN "01101",
	        b_temp(13 DOWNTO 0) & b_temp(31 DOWNTO 14) WHEN "01110",
	        b_temp(14 DOWNTO 0) & b_temp(31 DOWNTO 15) WHEN "01111",
	        b_temp(15 DOWNTO 0) & b_temp(31 DOWNTO 16) WHEN "10000",
           b_temp(16 DOWNTO 0) & b_temp(31 DOWNTO 17) WHEN "10001",
           b_temp(17 DOWNTO 0) & b_temp(31 DOWNTO 18) WHEN "10010",
	        b_temp(18 DOWNTO 0) & b_temp(31 DOWNTO 19) WHEN "10011",
	        b_temp(19 DOWNTO 0) & b_temp(31 DOWNTO 20) WHEN "10100",
	        b_temp(20 DOWNTO 0) & b_temp(31 DOWNTO 21) WHEN "10101",
	        b_temp(21 DOWNTO 0) & b_temp(31 DOWNTO 22) WHEN "10110",
	        b_temp(22 DOWNTO 0) & b_temp(31 DOWNTO 23) WHEN "10111",
	        b_temp(23 DOWNTO 0) & b_temp(31 DOWNTO 24) WHEN "11000",
	        b_temp(24 DOWNTO 0) & b_temp(31 DOWNTO 25) WHEN "11001",
	        b_temp(25 DOWNTO 0) & b_temp(31 DOWNTO 26) WHEN "11010",
	        b_temp(26 DOWNTO 0) & b_temp(31 DOWNTO 27) WHEN "11011",
           b_temp(27 DOWNTO 0) & b_temp(31 DOWNTO 28) WHEN "11100",
           b_temp(28 DOWNTO 0) & b_temp(31 DOWNTO 29) WHEN "11101",
	        b_temp(29 DOWNTO 0) & b_temp(31 DOWNTO 30) WHEN "11110",
           b_temp(30 DOWNTO 0) & b_temp(31) WHEN "11111",
           b_temp WHEN OTHERS; 
                b <= b_rot XOR a_reg;
                b_pre<=b-skey(1);
               
              

    -- A = ((A - S[2譱]) >>> B) xor B;
   
    a_temp<= a_reg-skey(CONV_INTEGER(i_cnt & '0'));
    
    WITH b(4 DOWNTO 0) SELECT
    a_rot<=a_temp(0) & a_temp(31 DOWNTO 1) WHEN "00001",
           a_temp(1 DOWNTO 0) & a_temp(31 DOWNTO 2) WHEN "00010",
	        a_temp(2 DOWNTO 0) & a_temp(31 DOWNTO 3) WHEN "00011",
	        a_temp(3 DOWNTO 0) & a_temp(31 DOWNTO 4) WHEN "00100",
	        a_temp(4 DOWNTO 0) & a_temp(31 DOWNTO 5) WHEN "00101",
	        a_temp(5 DOWNTO 0) & a_temp(31 DOWNTO 6) WHEN "00110",
          	a_temp(6 DOWNTO 0) & a_temp(31 DOWNTO 7) WHEN "00111",
          	a_temp(7 DOWNTO 0) & a_temp(31 DOWNTO 8) WHEN "01000",
	        a_temp(8 DOWNTO 0) & a_temp(31 DOWNTO 9) WHEN "01001",
	        a_temp(9 DOWNTO 0) & a_temp(31 DOWNTO 10) WHEN "01010",
	        a_temp(10 DOWNTO 0) & a_temp(31 DOWNTO 11) WHEN "01011",
           a_temp(11 DOWNTO 0) & a_temp(31 DOWNTO 12) WHEN "01100",
	        a_temp(12 DOWNTO 0) & a_temp(31 DOWNTO 13) WHEN "01101",
	        a_temp(13 DOWNTO 0) & a_temp(31 DOWNTO 14) WHEN "01110",
	        a_temp(14 DOWNTO 0) & a_temp(31 DOWNTO 15) WHEN "01111",
	        a_temp(15 DOWNTO 0) & a_temp(31 DOWNTO 16) WHEN "10000",
           a_temp(16 DOWNTO 0) & a_temp(31 DOWNTO 17) WHEN "10001",
           a_temp(17 DOWNTO 0) & a_temp(31 DOWNTO 18) WHEN "10010",
	        a_temp(18 DOWNTO 0) & a_temp(31 DOWNTO 19) WHEN "10011",
	        a_temp(19 DOWNTO 0) & a_temp(31 DOWNTO 20) WHEN "10100",
	        a_temp(20 DOWNTO 0) & a_temp(31 DOWNTO 21) WHEN "10101",
	        a_temp(21 DOWNTO 0) & a_temp(31 DOWNTO 22) WHEN "10110",
	        a_temp(22 DOWNTO 0) & a_temp(31 DOWNTO 23) WHEN "10111",
	        a_temp(23 DOWNTO 0) & a_temp(31 DOWNTO 24) WHEN "11000",
	        a_temp(24 DOWNTO 0) & a_temp(31 DOWNTO 25) WHEN "11001",
	        a_temp(25 DOWNTO 0) & a_temp(31 DOWNTO 26) WHEN "11010",
	        a_temp(26 DOWNTO 0) & a_temp(31 DOWNTO 27) WHEN "11011",
          	a_temp(27 DOWNTO 0) & a_temp(31 DOWNTO 28) WHEN "11100",
          	a_temp(28 DOWNTO 0) & a_temp(31 DOWNTO 29) WHEN "11101",
	        a_temp(29 DOWNTO 0) & a_temp(31 DOWNTO 30) WHEN "11110",
          	a_temp(30 DOWNTO 0) & a_temp(31) WHEN "11111",
           a_temp WHEN OTHERS; 
                a <= a_rot XOR b;
                a_pre<= a-skey(0);  
             
   
      -- B register
    PROCESS(clr, clk)  BEGIN
        IF(clr='0') THEN
           b_reg<= din(31 downto 0);
        ELSIF(clk'EVENT AND clk='1') THEN
           	IF(state=ST_PRE_ROUND) THEN 
           	
                   	b_reg<=b_pre;
           	ELSIF(state=ST_ROUND_OP) THEN 
           	b_reg<=b;
	        END IF;
        END IF;
    END PROCESS;   
   

    -- A register
    PROCESS(clr, clk)  BEGIN
        IF(clr='0') THEN
           a_reg<=din(63 downto 32); 
        ELSIF(clk'EVENT AND clk='1') THEN
           IF(state=ST_PRE_ROUND) THEN 
        
       		a_reg<=a_pre;
           ELSIF(state=ST_ROUND_OP) THEN   
			a_reg<=a;   
			  END IF;
        END IF;
    END PROCESS;


    -- round counter
    PROCESS(clr, clk)  
BEGIN
        IF(clr='0') THEN
           i_cnt<="1100";
        ELSIF(clk'EVENT AND clk='1') THEN
           IF(state= ST_ROUND_OP) THEN
             IF(i_cnt="0001") THEN  
             i_cnt<="1100";
             ELSE    
             i_cnt<=i_cnt-'1';    
             END IF;
           END IF;
        END IF;
    END PROCESS;

PROCESS(clr, clk)
BEGIN
      IF(clr='0') THEN
      state<=ST_IDLE;
      ELSIF(clk'EVENT AND clk='1') THEN
         CASE state IS
            WHEN ST_IDLE=> IF(di_vld='1') THEN 
                 state<=ST_ROUND_OP;  
                 END IF;
            WHEN ST_ROUND_OP=>IF(i_cnt="0010") THEN 
                 state<=ST_PRE_ROUND; 
                 END IF;
            WHEN ST_PRE_ROUND=>state<=ST_READY;
           
                              
            WHEN ST_READY=>state<=ST_IDLE;
         END CASE;
      END IF;
   END PROCESS;


    dout<=a_reg&b_reg;
    
    WITH state SELECT
        do_rdy<=	'1' WHEN ST_READY,
		           '0' WHEN OTHERS;

END do;