Subversion Repositories ttl_library

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

-- Bipolar TTL models (VHDL)                                         --

-- David R Brooks                                                    --

-- June, 2016.  Perth, Australia                                     --

-- Compliance: VHDL 2008                                             --

-- Testbench for SN74LS90AN: Decade counter (ripple)                 --

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

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_90 is     -- Top-level bench

generic(

    StimClk  : std_logic      := '0';

    CheckClk : std_logic      := '1';

    Period   : time           := 120 ns;

    Finish   : time           :=  20 us;

    SevLevel : severity_level := failure

);

end entity;

architecture Test of Testbench_90 is

    signal RS, NRS, C0 : std_logic;

    signal CLK         : std_logic;

    signal J,  B       : unsigned(1 downto 0);          -- Test stimuli

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

    begin

    RS <= not NRS;

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

    -- Standard testbench components

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

    TB: TTLBench

    generic map(

        StimClk  => StimClk,

        CheckClk => CheckClk,

        Period   => Period,

        Finish   => Finish,

        SevLevel => SevLevel

    )

    port map(

        J    => J,

        B    => B,

        CLK  => CLK,

        RS   => NRS,

        D    => D,

        E    => E

    );

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

    -- Generate expected results (with zero delays)

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

    process(B, RS) is

        variable Q0 : std_logic;

    begin

        if    RS = '1' then

            Q0 := '0';

        elsif falling_edge(B(0)) then

            Q0 := not Q0;

        end if;

        D(0) <= Q0;

    end process;

    process(D, RS) is

        variable Q31 : unsigned(2 downto 0);

    begin

        if    RS = '1' then

            Q31 := (others => '0');

        elsif falling_edge(D(0)) then

            case TTL_to_integer(Q31) is

                when 4 to 7 => Q31 := Q31 - 4;

                when others => Q31 := Q31 + 1;

            end case;

        end if;

        D(3 downto 1) <= std_logic_vector(Q31);

    end process;

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

    -- Device Under Test...                        

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

    DUT: SN74LS90AN

    port map(

    X_1  => C0,    -- CP1\

    X_2  => RS,    -- MR1

    X_3  => RS,    -- MR2

                   -- 

    X_5  => open,  -- Vcc

    X_6  => '0',   -- MS1

    X_7  => '0',   -- MS2

    X_8  => E(2),  -- Q2

    X_9  => E(1),  -- Q1

    X_10 => open,  -- GND

    X_11 => E(3),  -- Q3

    X_12 => C0,    -- Q0

                   -- 

    X_14 => B(0)   -- CP0\

);

    E(0) <= C0;

end architecture Test;