Subversion Repositories ttl_library

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

-- Bipolar TTL models (VHDL)                                         --

-- David R Brooks                                                    --

-- December, 2016.  Perth, Australia                                 --

-- Compliance: VHDL 2008                                             --

-- Testbench for SN74LS257N: Quad 2-input mux. (3-state outputs)      --

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

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_257 is     -- Top-level bench

generic(

    StimClk  : std_logic      := '1';

    CheckClk : std_logic      := '1';

    Period   : time           :=  50 ns;

    Finish   : time           :=  20 us;

    SevLevel : severity_level := failure

);

end entity;

architecture Test of Testbench_257 is

    signal J, B : unsigned(9 downto 0);         -- Test stimuli

    signal D, E : std_logic_vector(3 downto 0); -- Expected & actual results

    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)

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

    process(B) is

    begin

        if B(0) = '1' then

            D <= (others => 'Z');

        elsif B(1) = '0' then

            D <= (B(8), B(6), B(4), B(2));

        else

            D <= (B(9), B(7), B(5), B(3));

        end if;

    end process;

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

    -- Device Under Test...                        

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

    DUT: SN74LS257N

    port map(

    X_1  => B(1),  -- S

    X_2  => B(2),  -- I0A

    X_3  => B(3),  -- I1A

    X_4  => E(0),  -- ZA

    X_5  => B(4),  -- I0B

    X_6  => B(5),  -- I1B

    X_7  => E(1),  -- ZB

    X_8  => open,  -- GND

    X_9  => E(3),  -- ZD

    X_10 => B(9),  -- I1D

    X_11 => B(8),  -- I0D

    X_12 => E(2),  -- ZC

    X_13 => B(7),  -- I1C

    X_14 => B(6),  -- I0C

    X_15 => B(0),  -- E\

    X_16 => open   -- Vcc

);

end architecture Test;