Subversion Repositories ttl_library

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

-- Bipolar TTL models (VHDL)                                         --

-- David R Brooks                                                    --

-- June, 2016.  Perth, Australia                                     --

-- Compliance: VHDL 2008                                             --

-- Testbench for SN74LS138N: 1-of-8 decoder/demultiplexer            --

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

library ieee;

    use ieee.std_logic_1164.all;

    use ieee.std_logic_misc.all;

    use ieee.numeric_std.all;

    use work.LSTTL.all;

    use work.TTLPrivate.all;

entity Testbench_138 is     -- Top-level bench

generic(

    StimClk  : std_logic      := '1';

    CheckClk : std_logic      := '0';

    Period   : time           := 100 ns;

    Finish   : time           :=  20 us;

    SevLevel : severity_level := failure

);

end entity;

architecture Test of Testbench_138 is

    signal J, B : unsigned(5 downto 0);         -- Test stimuli

    signal D, E : std_logic_vector(7 downto 0); -- Expected & actual results

    signal EN   : std_logic;

    alias A  is J(2 downto 0);

    alias E1 is B(3);

    alias E2 is B(4);

    alias E3 is B(5);

    begin

    EN <= (not E1) and (not E2) and E3;

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

    -- Standard testbench components

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

    TB: TTLBench

    generic map(

        StimClk  => StimClk,

        CheckClk => CheckClk,

        Period   => Period,

        Finish   => Finish,

        SevLevel => SevLevel

    )

    port map(

        J   => J,

        B   => B,

        CLK => open,

        RS  => open,

        D   => D,

        E   => E

    );

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

    -- Generate expected results (with zero delays)

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

    process(A, EN) is

        variable chn : natural range 7 downto 0;

    begin

        E <= (others => '1');

        if EN = '1' then

            chn    := TTL_to_integer(A);

            E(chn) <= '0';

        end if;

    end process;

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

    -- Device Under Test...                        

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

    DUT: SN74LS138N

    port map(

    X_1  => A(0),  -- A0

    X_2  => A(1),  -- A1

    X_3  => A(2),  -- A2

    X_4  => E1,    -- E1\

    X_5  => E2,    -- E2\

    X_6  => E3,    -- E3

    X_7  => D(7),  -- O7\

    X_8  => open,  -- GND

    X_9  => D(6),  -- O6\

    X_10 => D(5),  -- O5\

    X_11 => D(4),  -- O4\

    X_12 => D(3),  -- O3\

    X_13 => D(2),  -- O2\

    X_14 => D(1),  -- O1\

    X_15 => D(0),  -- O0\

    X_16 => open   -- Vcc

);

end architecture Test;