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--##############################################################################

-- This file was generated automatically from '/src/mips_tb2_template.vhdl'.

-- 

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

-- Simulation test bench TB2 -- not synthesizable.

--

-- Simulates the CPU core connected to a simulated external static RAM and an

-- internal BRAM block through a stub (i.e. empty).

-- BRAM is initialized with the program object code, and SRAM is initialized 

-- with data secions from program. 

-- The makefile for the source samples include targets to build simulation test 

-- benches using this template, use them as usage examples.

--

-- The memory setup is meant to test the basic 'dummy' cache. 

-- 

-- Console output (at addresses compatible to Plasma's) is logged to text file

-- "hw_sim_console_log.txt".

-- IMPORTANT: The code that echoes UART TX data to the simulation console does

-- line buffering; it will not print anything until it gets a CR (0x0d), and

-- will ifnore LFs (0x0a). Bear this in mind if you see no output when you 

-- expect it.

--

-- WARNING: Will only work on Modelsim; uses custom library SignalSpy.

--##############################################################################

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

use std.textio.all;

use work.mips_pkg.all;

use work.mips_tb_pkg.all;

use work.txt_util.all;

entity @entity_name@ is

end;

architecture @arch_name@ of @entity_name@ is

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

-- Simulation parameters

-- Master clock period

constant T : time           := 20 ns;

-- Time the UART is unavailable after writing to the TX register

-- WARNING: slite does not simulate this. The logs may be different when > 0.0!

constant SIMULATED_UART_TX_TIME : time := 0.0 us;

-- Simulation length in clock cycles 

-- 2000 is enough for 'hello' sample, 22000 enough for 10 digits of pi

constant SIMULATION_LENGTH : integer := @sim_len@;

-- Simulated external SRAM size in 32-bit words 

constant SRAM_SIZE : integer := @xram_size@;

-- Ext. SRAM address length (memory is 16 bits wide so it needs an extra address bit)

constant SRAM_ADDR_SIZE : integer := log2(SRAM_SIZE)+1;

-- BRAM table and interface signals --------------------------------------------

constant BRAM_SIZE : integer := @code_table_size@;

constant BRAM_ADDR_SIZE : integer := @code_addr_size@;

subtype t_bram_address is std_logic_vector(BRAM_ADDR_SIZE-1 downto 0);

-- (this table holds one byte-slice; the RAM will have 4 of these)

type t_bram is array(0 to BRAM_SIZE-1) of std_logic_vector(7 downto 0);

signal bram_rd_addr :       t_bram_address;

signal bram_wr_addr :       t_bram_address;

signal bram_rd_data :       t_word;

signal bram_wr_data :       t_word;

signal bram_byte_we :       std_logic_vector(3 downto 0);

signal bram_data_rd_vma :   std_logic;

-- bram0 is LSB, bram3 is MSB

signal bram3 : t_bram := (@code3@);

signal bram2 : t_bram := (@code2@);

signal bram1 : t_bram := (@code1@);

signal bram0 : t_bram := (@code0@);

-- This is a 16-bit SRAM split in 2 byte slices; so each slice will have two

-- bytes for each word of SRAM_SIZE

type t_sram is array(0 to SRAM_SIZE*2-1) of std_logic_vector(7 downto 0);

signal sram1 : t_sram := (@data31@);

signal sram0 : t_sram := (@data20@);

signal data_uart :          std_logic_vector(31 downto 0);

signal data_uart_status :   std_logic_vector(31 downto 0);

signal uart_tx_rdy :        std_logic := '1';

signal uart_rx_rdy :        std_logic := '1';

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

signal clk :                std_logic := '0';

signal reset :              std_logic := '1';

signal interrupt :          std_logic := '0';

signal done :               std_logic := '0';

-- interface to asynchronous 16-bit-wide external SRAM

signal sram_address :       std_logic_vector(SRAM_ADDR_SIZE downto 1);

signal sram_databus :       std_logic_vector(15 downto 0);

signal sram_byte_we_n :     std_logic_vector(1 downto 0);

signal sram_oe_n :          std_logic;

-- interface cpu-cache

signal cpu_data_rd_addr :   t_word;

signal cpu_data_rd_vma :    std_logic;

signal cpu_data_rd :        t_word;

signal cpu_code_rd_addr :   t_pc;

signal cpu_code_rd :        t_word;

signal cpu_code_rd_vma :    std_logic;

signal cpu_data_wr_addr :   t_pc;

signal cpu_data_wr :        t_word;

signal cpu_byte_we :        std_logic_vector(3 downto 0);

signal cpu_mem_wait :       std_logic;

-- interface to i/o

signal io_rd_data :         std_logic_vector(31 downto 0);

signal io_wr_data :         std_logic_vector(31 downto 0);

signal io_rd_addr :         std_logic_vector(31 downto 2);

signal io_wr_addr :         std_logic_vector(31 downto 2);

signal io_rd_vma :          std_logic;

signal io_byte_we :         std_logic_vector(3 downto 0);

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

-- Logging signals

-- Log file

file log_file: TEXT open write_mode is "hw_sim_log.txt";

-- Console output log file

file con_file: TEXT open write_mode is "hw_sim_console_log.txt";

-- Maximum line size of for console output log. Lines longer than this will be

-- truncated.

constant CONSOLE_LOG_LINE_SIZE : integer := 1024*4;

-- Console log line buffer

signal con_line_buf :       string(1 to CONSOLE_LOG_LINE_SIZE);

signal con_line_ix :        integer := 1;

signal log_info :           t_log_info;

-- Debug signals ---------------------------------------------------------------

signal full_rd_addr :       std_logic_vector(31 downto 0);

signal full_wr_addr :       std_logic_vector(31 downto 0);

signal full_code_addr :     std_logic_vector(31 downto 0);

begin

    cpu: entity work.mips_cpu

    port map (

        interrupt   => '0',

        data_rd_addr=> cpu_data_rd_addr,

        data_rd_vma => cpu_data_rd_vma,

        data_rd     => cpu_data_rd,

        code_rd_addr=> cpu_code_rd_addr,

        code_rd     => cpu_code_rd,

        code_rd_vma => cpu_code_rd_vma,

        data_wr_addr=> cpu_data_wr_addr,

        data_wr     => cpu_data_wr,

        byte_we     => cpu_byte_we,

        mem_wait    => cpu_mem_wait,

        clk         => clk,

        reset       => reset

    );

    cache: entity work.mips_cache_stub

    generic map (

        BRAM_ADDR_SIZE => BRAM_ADDR_SIZE,

        SRAM_ADDR_SIZE => SRAM_ADDR_SIZE

    )

    port map (

        clk             => clk,

        reset           => reset,

        -- Interface to CPU core

        data_rd_addr    => cpu_data_rd_addr,

        data_rd         => cpu_data_rd,

        data_rd_vma     => cpu_data_rd_vma,

        code_rd_addr    => cpu_code_rd_addr,

        code_rd         => cpu_code_rd,

        code_rd_vma     => cpu_code_rd_vma,

        data_wr_addr    => cpu_data_wr_addr,

        byte_we         => cpu_byte_we,

        data_wr         => cpu_data_wr,

        mem_wait        => cpu_mem_wait,

        cache_enable    => '1',

        -- interface to FPGA i/o devices

        io_rd_data      => io_rd_data,

        io_wr_data      => io_wr_data,

        io_rd_addr      => io_rd_addr,

        io_wr_addr      => io_wr_addr,

        io_rd_vma       => io_rd_vma,

        io_byte_we      => io_byte_we,

        -- interface to synchronous 32-bit-wide FPGA BRAM

        bram_rd_data    => bram_rd_data,

        bram_wr_data    => bram_wr_data,

        bram_rd_addr    => bram_rd_addr,

        bram_wr_addr    => bram_wr_addr,

        bram_byte_we    => bram_byte_we,

        bram_data_rd_vma=> bram_data_rd_vma,

        -- interface to asynchronous 16-bit-wide external SRAM

        sram_address    => sram_address,

        sram_databus    => sram_databus,

        sram_byte_we_n  => sram_byte_we_n,

        sram_oe_n       => sram_oe_n

    );

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

    -- Master clock: free running clock used as main module clock

    run_master_clock:

    process(done, clk)

    begin

        if done = '0' then

            clk <= not clk after T/2;

        end if;

    end process run_master_clock;

    drive_uut:

    process

    variable l : line;

    begin

        wait for T*4;

        reset <= '0';

        wait for T*SIMULATION_LENGTH;

        -- Flush console output to log console file (in case the end of the

        -- simulation caugh an unterminated line in the buffer)

        if con_line_ix > 1 then

            write(l, con_line_buf(1 to con_line_ix));

            writeline(con_file, l);

        end if;

        print("TB0 finished");

        done <= '1';

        wait;

    end process drive_uut;

    full_rd_addr <= cpu_data_rd_addr;

    full_wr_addr <= cpu_data_wr_addr & "00";

    full_code_addr <= cpu_code_rd_addr & "00";

    data_ram_block:

    process(clk)

    begin

        if clk'event and clk='1' then

            if reset='0' then

                bram_rd_data <=

                    bram3(conv_integer(unsigned(bram_rd_addr))) &

                    bram2(conv_integer(unsigned(bram_rd_addr))) &

                    bram1(conv_integer(unsigned(bram_rd_addr))) &

                    bram0(conv_integer(unsigned(bram_rd_addr)));

                if bram_byte_we(3)='1' then

                    bram3(conv_integer(unsigned(bram_wr_addr))) <= cpu_data_wr(31 downto 24);

                end if;

                if bram_byte_we(2)='1' then

                    bram2(conv_integer(unsigned(bram_wr_addr))) <= cpu_data_wr(23 downto 16);

                end if;

                if bram_byte_we(1)='1' then

                    bram1(conv_integer(unsigned(bram_wr_addr))) <= cpu_data_wr(15 downto  8);

                end if;

                if bram_byte_we(0)='1' then

                    bram0(conv_integer(unsigned(bram_wr_addr))) <= cpu_data_wr( 7 downto  0);

                end if;

            end if;

        end if;

    end process data_ram_block;

    sram_databus <=

        sram1(conv_integer(unsigned(sram_address))) &

        sram0(conv_integer(unsigned(sram_address)))   when sram_oe_n='0'

        else (others => 'Z');

    -- Do a very basic simulation of an external SRAM

    simulated_sram:

    process(sram_byte_we_n, sram_address, sram_oe_n)

    begin

        -- Write cycle

        -- FIXME should add OE\ to write control logic

        if sram_byte_we_n'event or sram_address'event then

            if sram_byte_we_n(1)='0' then

                sram1(conv_integer(unsigned(sram_address))) <= sram_databus(15 downto  8);

            end if;

            if sram_byte_we_n(0)='0' then

                sram0(conv_integer(unsigned(sram_address))) <= sram_databus( 7 downto  0);

            end if;

        end if;

        -- Read cycle

        -- FIXME should add some verification of /WE 

        if sram_oe_n'event or sram_address'event then

            if sram_oe_n='0' then

                sram_databus <=

                    sram1(conv_integer(unsigned(sram_address))) &

                    sram0(conv_integer(unsigned(sram_address)));

            else

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

            end if;

        end if;

    end process simulated_sram;

    simulated_io:

    process(clk)

    variable i : integer;

    variable uart_data : integer;

    begin

        if clk'event and clk='1' then

            if io_byte_we/="0000" then

                if io_wr_addr(31 downto 28)=X"2" then

                    -- Write to UART

                    -- If we're simulating the UART TX time, pulse RDY low

                    if SIMULATED_UART_TX_TIME > 0 us then

                        uart_tx_rdy <= '0', '1' after SIMULATED_UART_TX_TIME;

                    end if;

                    -- TX data may come from the high or low byte (opcodes.s

                    -- uses high byte, no_op.c uses low)

                    if io_byte_we(0)='1' then

                        uart_data := conv_integer(unsigned(io_wr_data(7 downto 0)));

                    else

                        uart_data := conv_integer(unsigned(io_wr_data(31 downto 24)));

                    end if;

                    -- UART TX data goes to output after a bit of line-buffering

                    -- and editing

                    if uart_data = 10 then

                        -- CR received: print output string and clear it

                        print(con_file, con_line_buf(1 to con_line_ix));

                        con_line_ix <= 1;

                        for i in 1 to con_line_buf'high loop

                           con_line_buf(i) <= ' ';

                        end loop;

                    elsif uart_data = 13 then

                        -- ignore LF

                    else

                        -- append char to output string

                        if con_line_ix < con_line_buf'high then

                            con_line_buf(con_line_ix) <= character'val(uart_data);

                            con_line_ix <= con_line_ix + 1;

                        end if;

                    end if;

                end if;

            end if;

        end if;

    end process simulated_io;

    -- UART read registers; only status, and hardwired, for the time being

    io_rd_data <= X"00000003";

    data_uart <= data_uart_status;

    data_uart_status <= X"0000000" & "00" & uart_tx_rdy & uart_rx_rdy;

    log_execution:

    process

    begin

        log_cpu_activity(clk, reset, done,

                         "@entity_name@/cpu", log_info, "log_info", log_file);

        wait;

    end process log_execution;

end architecture @arch_name@;