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[/] [ttl_library/] [trunk/] [Testbench/] [Testbench_196.vhd] - Rev 4
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----------------------------------------------------------------------- -- Bipolar TTL models (VHDL) -- -- David R Brooks -- -- August, 2016. Perth, Australia -- -- Compliance: VHDL 2008 -- -- Testbench for SN74LS196N: Presettable decade counter -- ----------------------------------------------------------------------- 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_196 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_196 is signal RS, PL : std_logic; signal CLK, C0, C1 : std_logic; signal J, B : unsigned(3 downto 0); -- Test stimuli signal D, E, R : std_logic_vector(3 downto 0); -- Expected & actual results begin C0 <= CLK; R <= std_logic_vector(J); C1 <= D(0); ----------------------------------------------------------------------- -- 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 => RS, D => D, E => E ); ----------------------------------------------------------------------- -- Generate irregular LD signal ----------------------------------------------------------------------- process(RS, CLK) is variable N : natural; begin if RS = '0' then N := 1; PL <= '1'; elsif rising_edge(CLK) then if N >= 23 then N := 1; PL <= '0', '1' after 30 ns; else N := N + 1; end if; end if; end process; ----------------------------------------------------------------------- -- Generate expected results (with zero delays) ----------------------------------------------------------------------- process(C0, PL, RS, R) is variable Q0 : std_logic; begin if RS = '0' then Q0 := '0'; elsif PL = '0' then Q0 := R(0); elsif falling_edge(C0) then Q0 := not Q0; end if; D(0) <= Q0; end process; process(C1, PL, RS, R) is variable Q31 : unsigned(2 downto 0); begin if RS = '0' then Q31 := (others => '0'); elsif PL = '0' then Q31 := unsigned(R(3 downto 1)); elsif falling_edge(C1) 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: SN74LS196N port map( X_1 => PL, -- PL\ X_2 => E(2), -- Q2 X_3 => R(2), -- P2 X_4 => R(0), -- P0 X_5 => E(0), -- Q0 X_6 => C1, -- CP1\ X_7 => open, -- GND X_8 => C0, -- CP0\ X_9 => E(1), -- Q1 X_10 => R(1), -- P1 X_11 => R(3), -- P3 X_12 => E(3), -- Q3 X_13 => RS, -- MR\ X_14 => open -- Vcc ); end architecture Test;
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