Subversion Repositories ttl_library

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

-- Bipolar TTL models (VHDL)                                         --

-- David R Brooks                                                    --

-- December, 2016.  Perth, Australia                                 --

-- Compliance: VHDL 2008                                             --

-- Testbench for SN74LS253N: Dual 4-input mux. (common selects)      --

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

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_253 is     -- Top-level bench

generic(

    StimClk  : std_logic      := '1';

    CheckClk : std_logic      := '1';

    Period   : time           :=  50 ns;

    Finish   : time           := 200 us;

    SevLevel : severity_level := failure

);

end entity;

architecture Test of Testbench_253 is

    signal J, B : unsigned(7 downto 0);         -- Test stimuli

    signal D, E : std_logic_vector(1 downto 0); -- Expected & actual results

    signal A    : unsigned(1 downto 0);

    signal chn  : natural range 3 downto 0;

    begin

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

    -- 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)

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

    A    <= B(3 downto 2);

    chn  <= TTL_to_integer(A);

    D(0) <= B(7-chn) when B(0) = '0' else 'Z';

    D(1) <= B(chn+4) when B(1) = '0' else 'Z';

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

    -- Device Under Test...                        

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

    DUT: SN74LS253N

    port map(

    X_1  => B(0),  -- EA\

    X_2  => B(3),  -- S1

    X_3  => B(4),  -- I3A

    X_4  => B(5),  -- I2A

    X_5  => B(6),  -- I1A

    X_6  => B(7),  -- I0A

    X_7  => E(0),  -- ZA

    X_8  => open,  -- GND

    X_9  => E(1),  -- ZB

    X_10 => B(4),  -- I0B

    X_11 => B(5),  -- I1B

    X_12 => B(6),  -- I2B

    X_13 => B(7),  -- I3B

    X_14 => B(2),  -- S0

    X_15 => B(1),  -- EB\

    X_16 => open   -- Vcc

);

end architecture Test;