Subversion Repositories sha256_hash_core

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-- Author:          Jonny Doin, jdoin@opencores.org, jonnydoin@gmail.com, jonnydoin@gridvortex.com

-- 

-- Create Date:     09:56:30 05/22/2016  

-- Module Name:     sha256_test.vhd

-- Project Name:    sha256 engine

-- Target Devices:  Spartan-6

-- Tool versions:   ISE 14.7

-- Description: 

--

--      Testbench for the GV_SHA256 engine.

--      This is the testbench for the GV_SHA256 engine. It exercises all the input control signals and error generation,

--      and tests the GV_SHA256 engine with the NIST SHA256 test vectors, including the additional NIST test vectors up to the 

--      1 million chars.

--

--      The logic implements a fast engine, with 65 cycles per 512-bit block. 

--

--      The following waveforms describe the operation of the engine control signals for message start, update and end.

--

--      BEGIN BLOCK (1st block)

--      ======================

--

--      The hash operation starts with a 'begin' sync pulse, which causes the RESET of the processor. The processor comes out of RESET only after 'begin' is

--      released. 

--      The DATA_INPUT state is signalled by the data request signal 'di_req' going HIGH. The processor will latch 16 words from the 'di' port, at every 

--      rising edge of the system clock. At the end of the block input, the 'di_req' signal goes LOW. 

--      The input data can be held by bringing the 'wr_i' input LOW. When the 'wr_i' input is held LOW during data write, it inserts a wait state in the 

--      processor, to cope with slow inputs or to allow periodic fetches of input data from multiple data sources. 

--      The 'di_req' signal will remain HIGH while data input is requested. When all 16 words are clocked in, 'di_req' goes LOW, and 'wr_i' is not allowed

--      during the internal processing phase.

--

--      state              |reset| data                                    |wait |                                                     | process                  

--                    __   |__   |__    __    __    __    __    __    __   |__   |__    __    __    __    __    __    __    __    __   |__    __    __ 

--      clk_i      __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \...     -- system clock

--                        _____                                                                                                                                      

--      start_i    ______/   \_\_______________________________________________________________________________________________________________________...     -- 'start_i' resets the processor and starts a new hash

--                                                                                                                                                       

--      end_i      ____________________________________________________________________________________________________________________________________...     -- 'end_i' marks end of last block data input

--                 __ _ _ _       _____________________________________________________________________________________________________                  

--      di_req_o   __ _ _ _\_____/                                                                                                     \_______________...     -- 'di_req_o' asserted during data input

--                            ___________________________________________       _________________________________________________________                

--      wr_i       __________/____/                                      \_____/                                                         \_____________...     -- 'wr_i' can hold the core for slow data

--                 __________ _________ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ _____ ______ ______________...

--      di_i       __________\___\_W0__\__W1_\__W2_\__W3_\__W4_\__W5_\\\\\\\__W6_\__W7_\__W8_\__W9_\_W10_\_W11_\_W12_\_W13_\_W14_\_W15__\______X_______...     -- user words on 'di_i' are latched on 'clk_i' rising edge

--                 ____________________ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ _____ _____________________...

--      st_cnt_reg ________/__0__/__0__/__1__/__2__/__3__/__4__/__5__/___6_______/__7__/__8__/__9__/__10_/__11_/__12_/__13_/__14_/__15_/__16_/__17_/_18...     -- internal state counter value

--                 __________ ___ _____ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ _____ _____________________...

--      Wt_i@core  __________\___\__W0_\__W1_\__W2_\__W3_\__W4_\__W5_\\\\\\\__W6_\__W7_\__W8_\__W9_\_W10_\_W11_\_W12_\_W13_\_W14_\_W15_________________...     -- msg scheduler lookahead output for Wt_i at core

--                 ______________ _____ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ _____ _____________________...

--      Kt_i@core  ______________/__K0_/__K1_/__K2_/__K3_/__K4_/__K5_/__K6_______/__K7_/__K8_/__K9_/_K10_/_K11_/_K12_/_K13_/_K14_/_K15_________________...     -- Kt rom synchronous with scheduler for Kt_i at core

--                 __ _ _ _                                                                                                                                            

--      error_o    __ _ _ _\___________________________________________________________________________________________________________________________...     -- 'start_i' clears any error condition

--                 __ _ _ _                                                                                                                                            

--      do_valid_o __ _ _ _\___________________________________________________________________________________________________________________________...     -- 'start_i' invalidates any previous results

--

--

--      UPDATE BLOCK (preload)

--      =====================

--

--      At the start of each block, the 'di_req' signal is raised to request new data.

--

--      state       ... process  |next | data                                    |wait |                                                     | process                    

--                    __    __    __    __    __    __    __    __    __    __   |__   |__    __    __    __    __    __    __    __    __    __ 

--      clk_i      __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \...        -- system clock

--                                                                                                                                                  

--      end_i      ______________________________________________________________________________________________________________________________...        -- 'end_i' marks end of last block data input

--                                      _____________________________________________________________________________________________________       

--      di_req_o   ____________________/                                                                                                     \___...        -- 'di_req_o' asserted during data input

--                                       ______________________________________       _________________________________________________________     

--      wr_i       _____________________/                                      \_____/                                                         \_...        -- 'wr_i' can hold the core for slow data

--                 _________________ _ ______ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ _____ _____ ____...

--      di_i       _________________\\\___W0_\__W1_\__W2_\__W3_\__W4_\__W5_\\\\\\\\_W6_\__W7_\__W8_\__W9_\_W10_\_W11_\_W12_\_W13_\_W14_\_W15_\\_X_...       -- user words on 'di_i' are latched on 'clk_i' rising edge

--                 

--

--      UPDATE BLOCK (delayed start)

--      ===========================

--

--      The data for the new block can be delayed, by keeping the 'wr_i' signal low until the data is present at the data input port. 

--

--      state      ..|next | wait                  | data                                          |wait |                                         | process                    

--                    __    __    __    __    __   |__    __    __    __    __    __    __    __   |__   |__    __    __    __    __    __    __    __ 

--      clk_i      __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \...     -- system clock

--                                                                                                                                                       

--      end_i      ____________________________________________________________________________________________________________________________________...     -- 'end_i' marks end of last block data input

--                          _______ _ _ ___________________________________________________________________________________________________________      

--      di_req_o   ________/                                                                                                                       \___...     -- 'di_req_o' asserted during data input

--                                             __________________________________________________       _____________________________________________    

--      wr_i       ________________ _ _ ______/                                                  \_____/                                             \_...     -- 'wr_i' valid on rising edge of 'clk_i'

--                 ________________ _ _ ___________ _____ _____ _____ _____ _____ _____ _____ ___________ _____ _____ _____ _____ _____ _____ _____ ____...

--      di_i       ________________ _ _ ______\_W0_\__W1_\__W2_\__W3_\__W4_\__W5_\__W6_\__W7_\\\\_____W8_\__W9_\_W10_\_W11_\_W12_\_W13_\_W14_\_W15_\__Z_...     -- user words on 'di_i' are latched on 'clk_i' rising edge

--                 

--

--      END BLOCK (success)

--      ==================

--

--      At the end of the last block the signal 'end' must be raised for at least one clock cycle. 

--      The 'bytes' input marks the number of valid bytes in the last word. 

--      A PADDING state completes the last data block and a BLK_PROCESS finishes the hash computation.

--      The 'do_valid' remains HIGH until the next RESET.

--

--      state      ..|next | data                              | padding         | process                     |next | valid     |reset| data     

--                    __    __    __    __    __    __    __    __    __          __    __    __          __    __    __    __    __    __    __  

--      clk_i      __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \_ _ _ __/  \__/  \__/  \_ _ _ __/  \__/  \__/  \__/  \__/  \__/  \__/  \_...     -- system clock

--                                                                                                                              ______                    

--      start_i    ____________________________________________________________________________________________________________/   \__\___________...     -- 'start_i' resets the processor and starts a new hash

--                                                           ______                                                                               

--      end_i      _________________________________________/      \______ _ _ ___________________ _ _ ___________________________________________...     -- 'end_i' marks end of last block data input

--                          ___________________________________                                                                         __________  

--      di_req_o   ________/                                   \__________ _ _ ___________________ _ _ ________________________________/          ...     -- 'di_req_o' asserted during data input

--                           ______________________________________                                                                      _________  

--      wr_i       _________/                                    \\\______ _ _ ___________________ _ _ _________________________________/         ...     -- 'wr_i' can hold the core for slow data

--                 ______________ _____ _____ _____ _____ _____ __________ _ _ ___________________ _ _ ______________________________________ ____...

--      di_i       _________\_W0_\__W1_\__W2_\__W3_\__W4_\__W5_\__________ _ _ ___________________ _ _ _________________________________\_W0_\__W1...     -- words after the end_i assertion are ignored

--                 __ _____ _____ _____ _____ _____ _____ _____ _____ ____ _ ____ _____ _____ ____ _ _ ______________________________________ ____

--      st_cnt_reg __/_64__/__0__/__1__/__2__/__3__/__4__/__5__/__6__/__7_ _ _15_/__16_/__17_/__18 _ _ __/__63_/__64_/______0__________/__0__/__1_...     -- internal state counter value

--                          _____ _____ _____ _____ _____ _____                                                                         _____ ____

--      bytes_i    --------<__0__\__0__\__0__\__0__\__0__\__3__>-----------------------------------------------------------------------<__0__\__0_...     -- bytes_i mark number of valid bytes in each word

--                                                                                                                                                   

--      error_o    _______________________________________________________ _ _ ___________________ _ _ ___________________________________________...     -- 'error_o' goes high on an invalid computation

--                                                                                                                    ___________                 

--      do_valid_o _______________________________________________________ _ _ ___________________ _ _ ______________/           \________________...     -- 'do_valid_o' goes high at the end of a computation

--                                                                                                                    ___________                 

--      H0_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H0______\________________...     -- H0 holds the bytes 0..3 of the output

--                                                                                                                    ___________                                 

--      H1_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H1______\________________...     -- H1 holds the bytes 4..7 of the output

--                                                                                                                    ___________                            

--      H2_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H2______\________________...     -- H2 holds the bytes 8..11 of the output

--                                                                                                                    ___________                            

--      H3_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H3______\________________...     -- H3 holds the bytes 12..15 of the output

--                                                                                                                    ___________                            

--      H4_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H4______\________________...     -- H4 holds the bytes 16..19 of the output

--                                                                                                                    ___________                            

--      H5_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H5______\________________...     -- H5 holds the bytes 20..23 of the output

--                                                                                                                    ___________                            

--      H6_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H6______\________________...     -- H6 holds the bytes 24..27 of the output

--                                                                                                                    ___________                            

--      H7_o       _______________________________________________________ _ _ ___________________ _ _ ______________/___H7______\________________...     -- H7 holds the bytes 28..31 of the output

--

--

--      END BLOCK (full last block)

--      ==================

--

--      If the last block has exactly 16 full words, the controller starts the block processing in the PADDING cycle, processes the input block, 

--      and inserts a last PADDING block followed by a last BLK_PROCESS block.

--

--      state      ... data         |pad  | process   |next | pad                   | process   |next | valid     |reset| data

--                 __    __    __    __    __          __    __    __          __    __          __    __    __    __    __    __     

--      clk_i        \__/  \__/  \__/  \__/  \_ _ _ __/  \__/  \__/  \_ _ _ __/  \__/  \_ _ _ __/  \__/  \__/  \__/  \__/  \__/  \_...     -- system clock

--                                                                                                               ______                  

--      start_i    _____________________________________________________________________________________________/   \__\___________...     -- 'start_i' resets the processor and starts a new hash

--                                ______                                                                                                      

--      end_i      ______________/      \______ _ _ ___________________ _ _ _____________ _ _ _____________________________________...     -- 'end_i' marks end of last block data input

--                 _________________                                                                                     __________  

--      di_req_o                    \__________ _ _ ___________________ _ _ _____________ _ _ __________________________/          ...     -- 'di_req_o' asserted on rising edge of 'clk_i'

--                 ____________________                                                                                   _________  

--      wr_i                         \\\_______ _ _ ___________________ _ _ _____________ _ _ ___________________________/         ...     -- 'wr_i' valid on rising edge of 'clk_i'

--                 _____ _____ _____ __________ _ _ ___________________ _ _ _____________ _ _ ________________________________ ____...

--      di_i       _W13_\_W14_\_W15_\__________ _ _ ___________________ _ _ _____________ _ _ ___________________________\_W0_\__W1...     -- words after the end_i assertion are ignored

--                 _____ _____ _____ _____ ____ _ ____ _____ _____ ____ _ _ ________ ____ _ ____ _____ _______________________ ____

--      st_cnt_reg _13__/_14__/_15__/_16__/_17_ _ _63_/__64_/__0__/__1_ _ _ __/_15__/_16_ _ _63_/__64_/_____0_____/__0__/__0__/__1_...     -- internal state counter value

--                 _____ _____ _____                                                                                     _____ ____

--      bytes_i    __0__/__0__/__0__>-----------------------------------------------------------------------------------<__0__/__0_...     -- bytes_i mark number of valid bytes in each word

--                                                                                                     ___________                 

--      do_valid_o ____________________________ _ _ ___________________ _ _ __________________________/           \________________...     -- 'do_valid_o' goes high at the end of a computation

--

------------------------------ COPYRIGHT NOTICE -----------------------------------------------------------------------

--                                                                   

--      This file is part of the SHA256 HASH CORE project http://opencores.org/project,sha256_hash_core

--                                                                   

--      Author(s):      Jonny Doin, jdoin@opencores.org, jonnydoin@gridvortex.com, jonnydoin@gmail.com

--                                                                   

--      Copyright (C) 2016 Jonny Doin

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

--                                                                   

--      This source file may be used and distributed without restriction provided that this copyright statement is not    

--      removed from the file and that any derivative work contains the original copyright notice and the associated 

--      disclaimer. 

--                                                                   

--      This source file is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser 

--      General Public License as published by the Free Software Foundation; either version 2.1 of the License, or 

--      (at your option) any later version.

--                                                                   

--      This source is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied

--      warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more  

--      details.

--

--      You should have received a copy of the GNU Lesser General Public License along with this source; if not, download 

--      it from http://www.gnu.org/licenses/lgpl.txt

--                                                                   

------------------------------ REVISION HISTORY -----------------------------------------------------------------------

--

-- 2016/05/22   v0.01.0010  [JD]    started development. design of blocks and port interfaces.

-- 2016/06/05   v0.01.0090  [JD]    all modules integrated. testbench for basic test vectors verification.

-- 2016/06/05   v0.01.0095  [JD]    verification failed. misalignment of words in the datapath. 

-- 2016/06/06   v0.01.0100  [JD]    first simulation verification against NIST-FIPS-180-4 test vectors "abc" passed.

-- 2016/06/07   v0.01.0101  [JD]    failed 2-block test for "abcdbcdecd..." vector. Fixed padding control logic.

-- 2016/06/07   v0.01.0105  [JD]    sha256 verification against all NIST-FIPS-180-4 test vectors passed.

-- 2016/06/11   v0.01.0105  [JD]    verification against NIST-SHA2_Additional test vectors #1 to #10 passed.

-- 2016/06/11   v0.01.0110  [JD]    optimized controller states, reduced 2 clocks per block. 

-- 2016/06/18   v0.01.0120  [JD]    implemented error detection on 'bytes_i' input.

-- 2016/09/25   v0.01.0220  [JD]    changed 'di_ack_i' name to 'di_wr_i', and changed semantics to 'data write'.

-- 2016/10/01   v0.01.0250  [JD]    optimized the last null-padding state, making the algorithm isochronous for full last data blocks. 

--

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

--  TODO

--  ====

--

--

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library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

entity testbench is

    Generic (

        CLK_PERIOD : time := 10 ns;                     -- clock period for pclk_i (default 100MHz)

        START_DELAY : time := 200 ns                    -- start delay between each run

    );

end testbench;

architecture behavior of testbench is

    --=============================================================================================

    -- Constants

    --=============================================================================================

    -- clock period

    constant PCLK_PERIOD : time := CLK_PERIOD;          -- parallel high-speed clock

    --=============================================================================================

    -- Signals for state machine control

    --=============================================================================================

    --=============================================================================================

    -- Signals for internal operation

    --=============================================================================================

    --- clock signals ---

    signal pclk             : std_logic := '1';                 -- 100MHz clock

    signal dut_ce           : std_logic;

    -- input data

    signal dut_di           : std_logic_vector (31 downto 0);   -- big endian input message words

    signal dut_bytes        : std_logic_vector (1 downto 0);    -- valid bytes in input word

    -- start/end commands

    signal dut_start        : std_logic;                        -- reset the processor and start a new hash

    signal dut_end          : std_logic;                        -- marks end of last block data input

    -- handshake

    signal dut_di_req       : std_logic;                        -- requests data input for next word

    signal dut_di_wr        : std_logic;                        -- high for di_i write, low for hold

    signal dut_error        : std_logic;                        -- signalizes error. output data is invalid

    signal dut_do_valid     : std_logic;                        -- when high, the output is valid

    -- 256bit output registers

    signal dut_H0           : std_logic_vector (31 downto 0);

    signal dut_H1           : std_logic_vector (31 downto 0);

    signal dut_H2           : std_logic_vector (31 downto 0);

    signal dut_H3           : std_logic_vector (31 downto 0);

    signal dut_H4           : std_logic_vector (31 downto 0);

    signal dut_H5           : std_logic_vector (31 downto 0);

    signal dut_H6           : std_logic_vector (31 downto 0);

    signal dut_H7           : std_logic_vector (31 downto 0);

    -- testbench control signals

    signal words            : natural;

    signal blocks           : natural;

    signal test_case        : natural;

begin

    --=============================================================================================

    -- INSTANTIATION FOR THE DEVICE UNDER TEST

    --=============================================================================================

        Inst_sha_256_dut: entity work.gv_sha256(rtl)

        port map(

            -- clock and core enable

            clk_i => pclk,

            ce_i => dut_ce,

            -- input data

            di_i => dut_di,

            bytes_i => dut_bytes,

            -- start/end commands

            start_i => dut_start,

            end_i => dut_end,

            -- handshake

            di_req_o => dut_di_req,

            di_wr_i => dut_di_wr,

            error_o => dut_error,

            do_valid_o => dut_do_valid,

            -- 256bit output registers 

            H0_o => dut_H0,

            H1_o => dut_H1,

            H2_o => dut_H2,

            H3_o => dut_H3,

            H4_o => dut_H4,

            H5_o => dut_H5,

            H6_o => dut_H6,

            H7_o => dut_H7

        );

    --=============================================================================================

    -- CLOCK GENERATION

    --=============================================================================================

    pclk_proc: process is

    begin

        loop

            pclk <= not pclk;

            wait for PCLK_PERIOD / 2;

        end loop;

    end process pclk_proc;

    --=============================================================================================

    -- TEST BENCH STIMULI

    --=============================================================================================

    -- This testbench exercises the SHA256 toplevel with the NIST-FIPS-180-4 test vectors.

    --

    tb1 : process is

        variable count_words  : natural := 0;

        variable count_blocks : natural := 0;

        variable temp_di      : unsigned (31 downto 0) := (others => '0');

    begin

        wait for START_DELAY; -- wait until global set/reset completes

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

        -- test vector 1

        -- src: NIST-FIPS-180-4 

        -- msg := "abc" 

        -- hash:= BA7816BF 8F01CFEA 414140DE 5DAE2223 B00361A3 96177A9C B410FF61 F20015AD

        test_case <= 1;

        dut_ce <= '0';

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        dut_di <= x"61626300";

        dut_bytes <= b"11";

        wait until pclk'event and pclk = '1';

        dut_start <= '0';

        dut_di_wr <= '1';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        dut_end <= '1';

        wait until pclk'event and pclk = '1';

        dut_end <= '0';

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

        -- expected: BA7816BF 8F01CFEA 414140DE 5DAE2223 B00361A3 96177A9C B410FF61 F20015AD

        assert dut_H0 = x"BA7816BF" report "test #1 failed on H0" severity error;

        assert dut_H1 = x"8F01CFEA" report "test #1 failed on H1" severity error;

        assert dut_H2 = x"414140DE" report "test #1 failed on H2" severity error;

        assert dut_H3 = x"5DAE2223" report "test #1 failed on H3" severity error;

        assert dut_H4 = x"B00361A3" report "test #1 failed on H4" severity error;

        assert dut_H5 = x"96177A9C" report "test #1 failed on H5" severity error;

        assert dut_H6 = x"B410FF61" report "test #1 failed on H6" severity error;

        assert dut_H7 = x"F20015AD" report "test #1 failed on H7" severity error;

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

        -- test vector 2

        -- src: NIST-FIPS-180-4 

        -- msg := "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"

        -- hash:= 248D6A61 D20638B8 E5C02693 0C3E6039 A33CE459 64FF2167 F6ECEDD4 19DB06C1

        test_case <= 2;

        dut_ce <= '0';

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        wait until pclk'event and pclk = '1';   -- 'begin' pulse minimum width is one clock

        wait for 25 ns;                         -- TEST: stretch 'begin' pulse

        dut_start <= '0';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        wait until pclk'event and pclk = '1';

        dut_di_wr <= '1';

        dut_bytes <= b"00";

        dut_di <= x"61626364";

        wait until pclk'event and pclk = '1';

        dut_di <= x"62636465";

        wait until pclk'event and pclk = '1';

        dut_di <= x"63646566";

        wait until pclk'event and pclk = '1';

        dut_di <= x"64656667";

        wait until pclk'event and pclk = '1';

        dut_di <= x"65666768";

        wait until pclk'event and pclk = '1';

        dut_di <= x"66676869";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6768696A";

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        dut_di_wr <= '1';                      -- TEST: slow inputs with 'wr_i' handshake

        wait until pclk'event and pclk = '1';

        dut_di <= x"68696A6B";

        wait until pclk'event and pclk = '1';

        dut_di <= x"696A6B6C";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6A6B6C6D";

        dut_bytes <= b"01";                     -- induce ERROR

        wait until pclk'event and pclk = '1';

        dut_di <= x"6B6C6D6E";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6C6D6E6F";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6D6E6F70";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6E6F7071";

        dut_end <= '1';

        wait until pclk'event and pclk = '1';   -- 'end' pulse minimum width is one clock

        dut_bytes <= b"01";                     -- TEST: change 'bytes' value after END

        wait for 75 ns;                         -- TEST: stretch 'end' pulse

        dut_end <= '0';

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

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

        -- restart test #2: force error by stretching the write strobe

        dut_ce <= '0';

        test_case <= 0;

        wait until pclk'event and pclk = '1';

        test_case <= 2;

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        wait until pclk'event and pclk = '1';   -- 'begin' pulse minimum width is one clock

        wait for 25 ns;                         -- TEST: stretch 'begin' pulse

        dut_start <= '0';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        wait until pclk'event and pclk = '1';

        dut_di_wr <= '1';

        dut_bytes <= b"00";

        dut_di <= x"61626364";

        wait until pclk'event and pclk = '1';

        dut_di <= x"62636465";

        wait until pclk'event and pclk = '1';

        dut_di <= x"63646566";

        wait until pclk'event and pclk = '1';

        dut_di <= x"64656667";

        wait until pclk'event and pclk = '1';

        dut_di <= x"65666768";

        wait until pclk'event and pclk = '1';

        dut_di <= x"66676869";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6768696A";

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        wait until pclk'event and pclk = '1';

        dut_di_wr <= '1';                      -- TEST: slow inputs with 'wr_i' handshake

        wait until pclk'event and pclk = '1';

        dut_di <= x"68696A6B";

        wait until pclk'event and pclk = '1';

        dut_di <= x"696A6B6C";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6A6B6C6D";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6B6C6D6E";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6C6D6E6F";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6D6E6F70";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6E6F7071";

        wait for 75 ns;

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

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

        -- restart test #2

        dut_ce <= '0';

        test_case <= 0;

        wait until pclk'event and pclk = '1';

        test_case <= 2;

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        dut_di <= x"61626364";

        dut_bytes <= b"00";

        wait until pclk'event and pclk = '1';   -- 'begin' pulse minimum width is one clock

        dut_start <= '0';

        dut_di_wr <= '1';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        wait until pclk'event and pclk = '1';

        dut_di <= x"62636465";

        wait until pclk'event and pclk = '1';

        dut_di <= x"63646566";

        wait until pclk'event and pclk = '1';

        dut_di <= x"64656667";

        wait until pclk'event and pclk = '1';

        dut_di <= x"65666768";

        wait until pclk'event and pclk = '1';

        dut_di <= x"66676869";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6768696A";

        wait until pclk'event and pclk = '1';

        dut_di <= x"68696A6B";

        wait until pclk'event and pclk = '1';

        dut_di <= x"696A6B6C";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6A6B6C6D";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6B6C6D6E";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6C6D6E6F";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6D6E6F70";

        wait until pclk'event and pclk = '1';

        dut_di <= x"6E6F7071";

        dut_end <= '1';

        wait until pclk'event and pclk = '1';   -- 'end' pulse minimum width is one clock

        dut_end <= '0';

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

        -- expected: 248D6A61 D20638B8 E5C02693 0C3E6039 A33CE459 64FF2167 F6ECEDD4 19DB06C1

        assert dut_H0 = x"248D6A61" report "test #2 failed on H0" severity error;

        assert dut_H1 = x"D20638B8" report "test #2 failed on H1" severity error;

        assert dut_H2 = x"E5C02693" report "test #2 failed on H2" severity error;

        assert dut_H3 = x"0C3E6039" report "test #2 failed on H3" severity error;

        assert dut_H4 = x"A33CE459" report "test #2 failed on H4" severity error;

        assert dut_H5 = x"64FF2167" report "test #2 failed on H5" severity error;

        assert dut_H6 = x"F6ECEDD4" report "test #2 failed on H6" severity error;

        assert dut_H7 = x"19DB06C1" report "test #2 failed on H7" severity error;

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

        -- test vector 3

        -- src: NIST-ADDITIONAL-SHA256

        -- #1) 1 byte 0xbd

        -- msg := x"bd"

        -- hash:= 68325720 aabd7c82 f30f554b 313d0570 c95accbb 7dc4b5aa e11204c0 8ffe732b

        test_case <= 3;

        dut_ce <= '0';

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        dut_di <= x"bd000000";

        dut_bytes <= b"01";

        wait until pclk'event and pclk = '1';

        dut_start <= '0';

        dut_di_wr <= '1';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        dut_end <= '1';

        wait until pclk'event and pclk = '1';

        dut_end <= '0';

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

        -- expected: 68325720 aabd7c82 f30f554b 313d0570 c95accbb 7dc4b5aa e11204c0 8ffe732b

        assert dut_H0 = x"68325720" report "test #3 failed on H0" severity error;

        assert dut_H1 = x"aabd7c82" report "test #3 failed on H1" severity error;

        assert dut_H2 = x"f30f554b" report "test #3 failed on H2" severity error;

        assert dut_H3 = x"313d0570" report "test #3 failed on H3" severity error;

        assert dut_H4 = x"c95accbb" report "test #3 failed on H4" severity error;

        assert dut_H5 = x"7dc4b5aa" report "test #3 failed on H5" severity error;

        assert dut_H6 = x"e11204c0" report "test #3 failed on H6" severity error;

        assert dut_H7 = x"8ffe732b" report "test #3 failed on H7" severity error;

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

        -- test vector 4

        -- src: NIST-ADDITIONAL-SHA256

        -- #2) 4 bytes 0xc98c8e55

        -- msg := x"c98c8e55"

        -- hash:= 7abc22c0 ae5af26c e93dbb94 433a0e0b 2e119d01 4f8e7f65 bd56c61c cccd9504

        test_case <= 4;

        dut_ce <= '0';

        dut_di <= (others => '0');

        dut_bytes <= b"00";

        dut_start <= '0';

        dut_end <= '0';

        dut_di_wr <= '0';

        wait until pclk'event and pclk = '1';

        dut_ce <= '1';

        dut_start <= '1';

        dut_di <= x"c98c8e55";

        dut_bytes <= b"00";

        wait until pclk'event and pclk = '1';

        dut_start <= '0';

        dut_di_wr <= '1';

        if dut_di_req = '0' then

            wait until dut_di_req = '1';

        end if;

        dut_di_wr <= '1';

        dut_end <= '1';

        wait until pclk'event and pclk = '1';

        dut_end <= '0';

        dut_di_wr <= '0';

        if dut_error /= '1' and dut_do_valid /= '1' then

            while dut_error /= '1' and dut_do_valid /= '1' loop

                wait until pclk'event and pclk = '1';

            end loop;

        end if;

        wait for CLK_PERIOD*20;

        -- expected: 7abc22c0 ae5af26c e93dbb94 433a0e0b 2e119d01 4f8e7f65 bd56c61c cccd9504 

        assert dut_H0 = x"7abc22c0" report "test #4 failed on H0" severity error;

        assert dut_H1 = x"ae5af26c" report "test #4 failed on H1" severity error;