rom.vhd

vhd语言

--"ROM.VHDL"
library IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY ROM IS
PORT ( A5,A4,A3,A2,A1,A0:IN STD_LOGIC;
       D1,D2,D3,D4,D5,D6,D7:OUT STD_LOGIC;
       D8,D9,D10,D11,D12,D13,D14:OUT STD_LOGIC;
       D15,D16,D17,D18,D19,D20,D21:OUT STD_LOGIC;
       D22,D23,D24,D25,D26,D27,D28,D29,D30,D31:OUT STD_LOGIC);
END ROM;
ARCHITECTURE BEHAVIORAL OF ROM IS
    SIGNAL SK : STD_LOGIC_VECTOR(5 DOWNTO 0);
    SIGNAL SEL: STD_LOGIC_VECTOR (30 DOWNTO 0);
    BEGIN
       SK<=A5&A4&A3&A2&A1&A0;
       SEL<="1011000000000001010000000000001"WHEN SK="000000" ELSE
            "1110100100000001010000000000010"WHEN SK="000001" ELSE
            "1101001100000001010011000100000"WHEN SK="000010" ELSE
            "1110100100000001010000000010000"WHEN SK="100000" ELSE
            "1110100100000001010000000010010"WHEN SK="100001" ELSE
            "1101000110000001000000000010100"WHEN SK="100010" ELSE
            "1101000110000001000000000010110"WHEN SK="100011" ELSE
            "1101000110000001000000000011000"WHEN SK="100100" ELSE
            "1101000110000001000000000011010"WHEN SK="100101" ELSE
            "1101000110000001000000000011100"WHEN SK="100110" ELSE
            "1101000100000001010000100110000"WHEN SK="100111" ELSE
            "1101000100000001010000010110011"WHEN SK="101000" ELSE
            "1101101100000001010000000010001"WHEN SK="010000" ELSE
            "1101001100000001110000000000001"WHEN SK="010001" ELSE
            "1101101100000001010000000010011"WHEN SK="010010" ELSE
            "1101010100000001000000000000001"WHEN SK="010011" ELSE
            "1101000100000001001100000010101"WHEN SK="010100" ELSE
            "1101000100100110110000000000001"WHEN SK="010101" ELSE
            "1101000100000001001100000010111"WHEN SK="010110" ELSE
            "1101000100011000110000000000001"WHEN SK="010111" ELSE
            "1101000100000001001100000011001"WHEN SK="011000" ELSE
            "1101000100101100110000000000001"WHEN SK="011001" ELSE
            "1101000100000001001100000011011"WHEN SK="011010" ELSE
            "1101000100000110110000000000001"WHEN SK="011011" ELSE
            "1101000100000001001100000011101"WHEN SK="011100" ELSE
            "1101000100000000110000001000001"WHEN SK="011101" ELSE
            "1110100100000001010000000001000"WHEN SK="110000" ELSE
            "1011001100000001010000000000001"WHEN SK="001000" ELSE
            "1110100100000001010000000001001"WHEN SK="110100" ELSE
            "1011001100000001010000000000001"WHEN SK="001001" ELSE
            "1110100100000001010000000001010"WHEN SK="111000" ELSE
            "1011001100000001010000000000001"WHEN SK="001010" ELSE
            "1110100100000001010000000001011"WHEN SK="111100" ELSE
            "1011001100000001010000000000001"WHEN SK="001011" ELSE
            "1101000000000001110000000000001"WHEN SK="110111" ELSE
            "1101000100000001000000000000001"WHEN SK="111011" ELSE
            "0101000100000001010000000111111"WHEN SK="110011";





D1<=SEL(30);D2<=SEL(29); D3<=SEL(28); D4<=SEL(27);D5<=SEL(26);
D6<=SEL(25); D7<=SEL(24); D8<=SEL(23); D9<=SEL(22);
D10<=SEL(21); D11<=SEL(20); D12<=SEL(19);D13<=SEL(18);
D14<=SEL(17); D15<=SEL(16); D16<=SEL(15); D17<=SEL(14);
D18<=SEL(13); D19<=SEL(12);D20<=SEL(11); D21<=SEL(10);
D22<=SEL(9); D23<=SEL(8);D24<=SEL(7);D25<=SEL(6);
D26<=SEL(5); D27<=SEL(4); D28<=SEL(3);D29<=SEL(2);
D30<=SEL(1);D31<=SEL(0);
END BEHAVIORAL;