Subversion Repositories neorv32

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

-- # << NEORV32 - Processor Top Entity >>                                                          #

-- # ********************************************************************************************* #

-- # This is the top entity of the NEORV32 Processor. Instantiate this unit in your own project    #

-- # and define all the configuration generics according to your needs. Alternatively, you can use #

-- # one of the alternative top entities provided in the "rtl\top_templates" folder.               #

-- # Check the processor's documentary for more information: doc\NEORV32.pdf                       #

-- # ********************************************************************************************* #

-- # BSD 3-Clause License                                                                          #

-- #                                                                                               #

-- # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #

-- #                                                                                               #

-- # Redistribution and use in source and binary forms, with or without modification, are          #

-- # permitted provided that the following conditions are met:                                     #

-- #                                                                                               #

-- # 1. Redistributions of source code must retain the above copyright notice, this list of        #

-- #    conditions and the following disclaimer.                                                   #

-- #                                                                                               #

-- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of     #

-- #    conditions and the following disclaimer in the documentation and/or other materials        #

-- #    provided with the distribution.                                                            #

-- #                                                                                               #

-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #

-- #    endorse or promote products derived from this software without specific prior written      #

-- #    permission.                                                                                #

-- #                                                                                               #

-- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #

-- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #

-- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #

-- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #

-- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #

-- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #

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-- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #

-- # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #

-- # ********************************************************************************************* #

-- # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

library neorv32;

use neorv32.neorv32_package.all;

entity neorv32_top is

  generic (

    -- General --

    CLOCK_FREQUENCY           : natural := 0; -- clock frequency of clk_i in Hz

    HART_ID                   : std_ulogic_vector(31 downto 0) := x"00000000"; -- custom hardware thread ID

    BOOTLOADER_USE            : boolean := true;   -- implement processor-internal bootloader?

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_C     : boolean := false;  -- implement compressed extension?

    CPU_EXTENSION_RISCV_E     : boolean := false;  -- implement embedded RF extension?

    CPU_EXTENSION_RISCV_M     : boolean := false;  -- implement muld/div extension?

    CPU_EXTENSION_RISCV_Zicsr : boolean := true;   -- implement CSR system?

    -- Memory configuration: Instruction memory --

    MEM_ISPACE_BASE           : std_ulogic_vector(31 downto 0) := x"00000000"; -- base address of instruction memory space

    MEM_ISPACE_SIZE           : natural := 16*1024; -- total size of instruction memory space in byte

    MEM_INT_IMEM_USE          : boolean := true;   -- implement processor-internal instruction memory

    MEM_INT_IMEM_SIZE         : natural := 16*1024; -- size of processor-internal instruction memory in bytes

    MEM_INT_IMEM_ROM          : boolean := false;  -- implement processor-internal instruction memory as ROM

    -- Memory configuration: Data memory --

    MEM_DSPACE_BASE           : std_ulogic_vector(31 downto 0) := x"80000000"; -- base address of data memory space

    MEM_DSPACE_SIZE           : natural := 8*1024; -- total size of data memory space in byte

    MEM_INT_DMEM_USE          : boolean := true;   -- implement processor-internal data memory

    MEM_INT_DMEM_SIZE         : natural := 8*1024; -- size of processor-internal data memory in bytes

    -- Memory configuration: External memory interface --

    MEM_EXT_USE               : boolean := false;  -- implement external memory bus interface?

    MEM_EXT_REG_STAGES        : natural := 2;      -- number of interface register stages (0,1,2)

    MEM_EXT_TIMEOUT           : natural := 15;     -- cycles after which a valid bus access will timeout

    -- Processor peripherals --

    IO_GPIO_USE               : boolean := true;   -- implement general purpose input/output port unit (GPIO)?

    IO_MTIME_USE              : boolean := true;   -- implement machine system timer (MTIME)?

    IO_UART_USE               : boolean := true;   -- implement universal asynchronous receiver/transmitter (UART)?

    IO_SPI_USE                : boolean := true;   -- implement serial peripheral interface (SPI)?

    IO_TWI_USE                : boolean := true;   -- implement two-wire interface (TWI)?

    IO_PWM_USE                : boolean := true;   -- implement pulse-width modulation unit (PWM)?

    IO_WDT_USE                : boolean := true;   -- implement watch dog timer (WDT)?

    IO_CLIC_USE               : boolean := true;   -- implement core local interrupt controller (CLIC)?

    IO_TRNG_USE               : boolean := false   -- implement true random number generator (TRNG)?

  );

  port (

    -- Global control --

    clk_i      : in  std_ulogic := '0'; -- global clock, rising edge

    rstn_i     : in  std_ulogic := '0'; -- global reset, low-active, async

    -- Wishbone bus interface (available if MEM_EXT_USE = true) --

    wb_adr_o   : out std_ulogic_vector(31 downto 0); -- address

    wb_dat_i   : in  std_ulogic_vector(31 downto 0) := (others => '0'); -- read data

    wb_dat_o   : out std_ulogic_vector(31 downto 0); -- write data

    wb_we_o    : out std_ulogic; -- read/write

    wb_sel_o   : out std_ulogic_vector(03 downto 0); -- byte enable

    wb_stb_o   : out std_ulogic; -- strobe

    wb_cyc_o   : out std_ulogic; -- valid cycle

    wb_ack_i   : in  std_ulogic := '0'; -- transfer acknowledge

    wb_err_i   : in  std_ulogic := '0'; -- transfer error

    -- GPIO (available if IO_GPIO_USE = true) --

    gpio_o     : out std_ulogic_vector(15 downto 0); -- parallel output

    gpio_i     : in  std_ulogic_vector(15 downto 0) := (others => '0'); -- parallel input

    -- UART (available if IO_UART_USE = true) --

    uart_txd_o : out std_ulogic; -- UART send data

    uart_rxd_i : in  std_ulogic := '0'; -- UART receive data

    -- SPI (available if IO_SPI_USE = true) --

    spi_sclk_o : out std_ulogic; -- serial clock line

    spi_mosi_o : out std_ulogic; -- serial data line out

    spi_miso_i : in  std_ulogic := '0'; -- serial data line in

    spi_csn_o  : out std_ulogic_vector(07 downto 0); -- SPI CS

    -- TWI (available if IO_TWI_USE = true) --

    twi_sda_io : inout std_logic := 'H'; -- twi serial data line

    twi_scl_io : inout std_logic := 'H'; -- twi serial clock line

    -- PWM (available if IO_PWM_USE = true) --

    pwm_o      : out std_ulogic_vector(03 downto 0);  -- pwm channels

    -- Interrupts (available if IO_CLIC_USE = true) --

    ext_irq_i  : in  std_ulogic_vector(01 downto 0) := (others => '0'); -- external interrupt request

    ext_ack_o  : out std_ulogic_vector(01 downto 0)  -- external interrupt request acknowledge

  );

end neorv32_top;

architecture neorv32_top_rtl of neorv32_top is

  -- reset generator --

  signal rstn_i_sync0 : std_ulogic;

  signal rstn_i_sync1 : std_ulogic;

  signal rstn_i_sync2 : std_ulogic;

  signal rstn_gen     : std_ulogic_vector(3 downto 0);

  signal ext_rstn     : std_ulogic;

  signal sys_rstn     : std_ulogic;

  signal wdt_rstn     : std_ulogic;

  -- clock generator --

  signal clk_div    : std_ulogic_vector(11 downto 0);

  signal clk_div_ff : std_ulogic_vector(11 downto 0);

  signal clk_gen    : std_ulogic_vector(07 downto 0);

  signal wdt_cg_en  : std_ulogic;

  signal uart_cg_en : std_ulogic;

  signal spi_cg_en  : std_ulogic;

  signal twi_cg_en  : std_ulogic;

  signal pwm_cg_en  : std_ulogic;

  -- cpu bus --

  signal cpu_addr  : std_ulogic_vector(data_width_c-1 downto 0); -- bus access address

  signal cpu_rdata : std_ulogic_vector(data_width_c-1 downto 0); -- bus read data

  signal cpu_wdata : std_ulogic_vector(data_width_c-1 downto 0); -- bus write data

  signal cpu_ben   : std_ulogic_vector(03 downto 0); -- byte enable

  signal cpu_we    : std_ulogic; -- write enable

  signal cpu_re    : std_ulogic; -- read enable

  signal cpu_ack   : std_ulogic; -- bus transfer acknowledge

  signal cpu_err   : std_ulogic; -- bus transfer error

  -- io space access --

  signal io_acc  : std_ulogic;

  signal io_rden : std_ulogic;

  signal io_wren : std_ulogic;

  -- read-back busses -

  signal imem_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal imem_ack       : std_ulogic;

  signal dmem_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal dmem_ack       : std_ulogic;

  signal bootrom_rdata  : std_ulogic_vector(data_width_c-1 downto 0);

  signal bootrom_ack    : std_ulogic;

  signal wishbone_rdata : std_ulogic_vector(data_width_c-1 downto 0);

  signal wishbone_ack   : std_ulogic;

  signal wishbone_err   : std_ulogic;

  signal gpio_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal gpio_ack       : std_ulogic;

  signal mtime_rdata    : std_ulogic_vector(data_width_c-1 downto 0);

  signal mtime_ack      : std_ulogic;

  signal uart_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal uart_ack       : std_ulogic;

  signal spi_rdata      : std_ulogic_vector(data_width_c-1 downto 0);

  signal spi_ack        : std_ulogic;

  signal twi_rdata      : std_ulogic_vector(data_width_c-1 downto 0);

  signal twi_ack        : std_ulogic;

  signal pwm_rdata      : std_ulogic_vector(data_width_c-1 downto 0);

  signal pwm_ack        : std_ulogic;

  signal wdt_rdata      : std_ulogic_vector(data_width_c-1 downto 0);

  signal wdt_ack        : std_ulogic;

  signal clic_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal clic_ack       : std_ulogic;

  signal trng_rdata     : std_ulogic_vector(data_width_c-1 downto 0);

  signal trng_ack       : std_ulogic;

  -- IRQs --

  signal mtime_irq : std_ulogic;

  signal clic_irq  : std_ulogic;

  signal clic_xirq : std_ulogic_vector(7 downto 0);

  signal clic_xack : std_ulogic_vector(7 downto 0);

  signal gpio_irq  : std_ulogic;

  signal wdt_irq   : std_ulogic;

  signal uart_irq  : std_ulogic;

  signal spi_irq   : std_ulogic;

  signal twi_irq   : std_ulogic;

begin

  -- Sanity Checks --------------------------------------------------------------------------

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

  sanity_check: process(clk_i)

  begin

    if rising_edge(clk_i) then

      -- internal bootloader memory --

      if (BOOTLOADER_USE = true) and (boot_size_c > boot_max_size_c) then

        assert false report "NEORV32 CONFIG ERROR! Boot ROM size out of range." severity error;

      end if;

      -- memory system - data/instruction fetch --

      if (MEM_EXT_USE = false) then

        if (MEM_INT_DMEM_USE = false) then

          assert false report "NEORV32 CONFIG ERROR! Core cannot fetch data without external memory interface and internal data memory." severity error;

        end if;

        if (MEM_INT_IMEM_USE = false) and (BOOTLOADER_USE = false) then

          assert false report "NEORV32 CONFIG ERROR! Core cannot fetch instructions without external memory interface, internal data memory and bootloader." severity error;

        end if;

      end if;

      -- memory system - address space --

      if (MEM_INT_IMEM_USE = true) and (MEM_INT_IMEM_SIZE > MEM_ISPACE_SIZE) then

        assert false report "NEORV32 CONFIG ERROR! Internal instruction memory (IMEM) cannot be greater than total instruction address space." severity error;

      end if;

      if (MEM_INT_DMEM_USE = true) and (MEM_INT_DMEM_SIZE > MEM_DSPACE_SIZE) then

        assert false report "NEORV32 CONFIG ERROR! Internal data memory (DMEM) cannot be greater than total data address space." severity error;

      end if;

      if (MEM_EXT_TIMEOUT <= 1) then

        assert false report "NEORV32 CONFIG ERROR! Invalid bus timeout. Internal components require 1 cycle delay." severity error;

      end if;

      -- clock --

      if (CLOCK_FREQUENCY = 0) then

        assert false report "NEORV32 CONFIG ERROR! Core clock frequency (CLOCK_FREQUENCY) not specified." severity error;

      end if;

      -- CSR system not implemented --

      if (CPU_EXTENSION_RISCV_Zicsr = false) then

        assert false report "NEORV32 CONFIG WARNING! No exception/interrupt/machine status features available when CPU_EXTENSION_RISCV_Zicsr = false." severity warning;

      end if;

      -- core local interrupt controller --

      if (CPU_EXTENSION_RISCV_Zicsr = false) and (IO_CLIC_USE = true) then

        assert false report "NEORV32 CONFIG ERROR! Core local interrupt controller (CLIC) cannot be used without >Zicsr< CPU extension." severity error;

      end if;

      -- memory layout notifier --

      if (MEM_ISPACE_BASE /= x"00000000") then

        assert false report "NEORV32 CONFIG WARNING! Non-default base address for instruction address space. Make sure this is sync with the linker script." severity warning;

      end if;

      if (MEM_DSPACE_BASE /= x"80000000") then

        assert false report "NEORV32 CONFIG WARNING! Non-default base address for data address space. Make sure this is sync with the linker script." severity warning;

      end if;

    end if;

  end process sanity_check;

  -- Reset Generator ------------------------------------------------------------------------

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

  reset_generator_sync: process(clk_i)

  begin

    -- make sure the external reset is free of metastability and has a minimal duration of 1 clock cycle

    if rising_edge(clk_i) then

      rstn_i_sync0 <= rstn_i;

      rstn_i_sync1 <= rstn_i_sync0;

      rstn_i_sync2 <= rstn_i_sync1;

    end if;

  end process reset_generator_sync;

  -- keep internal reset active for at least 4 clock cycles

  reset_generator: process(rstn_i_sync1, rstn_i_sync2, clk_i)

  begin

    if ((rstn_i_sync1 or rstn_i_sync2) = '0') then -- signal stable somehow?

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

    elsif rising_edge(clk_i) then

      rstn_gen <= rstn_gen(rstn_gen'left-1 downto 0) & '1';

    end if;

  end process reset_generator;

  ext_rstn <= rstn_gen(rstn_gen'left); -- the beautified external reset signal

  sys_rstn <= ext_rstn and wdt_rstn; -- system reset - can also be triggered by watchdog

  -- Clock Generator ------------------------------------------------------------------------

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

  clock_generator: process(sys_rstn, clk_i)

  begin

    if (sys_rstn = '0') then

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

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

    elsif rising_edge(clk_i) then

      -- anybody wanting some fresh clocks? --

      if ((wdt_cg_en or uart_cg_en or spi_cg_en or twi_cg_en or pwm_cg_en) = '1') then

        clk_div    <= std_ulogic_vector(unsigned(clk_div) + 1);

        clk_div_ff <= clk_div;

      end if;

    end if;

  end process clock_generator;

  -- clock enable select: rising edge detectors --

  clk_gen(clk_div2_c)    <= clk_div(0)  and (not clk_div_ff(0));  -- CLK/2

  clk_gen(clk_div4_c)    <= clk_div(1)  and (not clk_div_ff(1));  -- CLK/4

  clk_gen(clk_div8_c)    <= clk_div(2)  and (not clk_div_ff(2));  -- CLK/8

  clk_gen(clk_div64_c)   <= clk_div(5)  and (not clk_div_ff(5));  -- CLK/64

  clk_gen(clk_div128_c)  <= clk_div(6)  and (not clk_div_ff(6));  -- CLK/128

  clk_gen(clk_div1024_c) <= clk_div(9)  and (not clk_div_ff(9));  -- CLK/1024

  clk_gen(clk_div2048_c) <= clk_div(10) and (not clk_div_ff(10)); -- CLK/2048

  clk_gen(clk_div4096_c) <= clk_div(11) and (not clk_div_ff(11)); -- CLK/4096

  -- CPU ------------------------------------------------------------------------------------

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

  neorv32_cpu_inst: neorv32_cpu

  generic map (

    -- General --

    CLOCK_FREQUENCY           => CLOCK_FREQUENCY,   -- clock frequency of clk_i in Hz

    HART_ID                   => HART_ID,           -- custom hardware thread ID

    BOOTLOADER_USE            => BOOTLOADER_USE,    -- implement processor-internal bootloader?

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_C     => CPU_EXTENSION_RISCV_C,     -- implement compressed extension?

    CPU_EXTENSION_RISCV_E     => CPU_EXTENSION_RISCV_E,     -- implement embedded RF extension?

    CPU_EXTENSION_RISCV_M     => CPU_EXTENSION_RISCV_M,     -- implement muld/div extension?

    CPU_EXTENSION_RISCV_Zicsr => CPU_EXTENSION_RISCV_Zicsr, -- implement CSR system?

    -- Memory configuration: Instruction memory --

    MEM_ISPACE_BASE           => MEM_ISPACE_BASE,   -- base address of instruction memory space

    MEM_ISPACE_SIZE           => MEM_ISPACE_SIZE,   -- total size of instruction memory space in byte

    MEM_INT_IMEM_USE          => MEM_INT_IMEM_USE,  -- implement processor-internal instruction memory

    MEM_INT_IMEM_SIZE         => MEM_INT_IMEM_SIZE, -- size of processor-internal instruction memory in bytes

    MEM_INT_IMEM_ROM          => MEM_INT_IMEM_ROM,  -- implement processor-internal instruction memory as ROM

    -- Memory configuration: Data memory --

    MEM_DSPACE_BASE           => MEM_DSPACE_BASE,   -- base address of data memory space

    MEM_DSPACE_SIZE           => MEM_DSPACE_SIZE,   -- total size of data memory space in byte

    MEM_INT_DMEM_USE          => MEM_INT_DMEM_USE,  -- implement processor-internal data memory

    MEM_INT_DMEM_SIZE         => MEM_INT_DMEM_SIZE, -- size of processor-internal data memory in bytes

    -- Memory configuration: External memory interface --

    MEM_EXT_USE               => MEM_EXT_USE,       -- implement external memory bus interface?

    MEM_EXT_TIMEOUT           => MEM_EXT_TIMEOUT,   -- cycles after which a valid bus access will timeout

    -- Processor peripherals --

    IO_GPIO_USE               => IO_GPIO_USE,       -- implement general purpose input/output port unit (GPIO)?

    IO_MTIME_USE              => IO_MTIME_USE,      -- implement machine system timer (MTIME)?

    IO_UART_USE               => IO_UART_USE,       -- implement universal asynchronous receiver/transmitter (UART)?

    IO_SPI_USE                => IO_SPI_USE,        -- implement serial peripheral interface (SPI)?

    IO_TWI_USE                => IO_TWI_USE,        -- implement two-wire interface (TWI)?

    IO_PWM_USE                => IO_PWM_USE,        -- implement pulse-width modulation unit (PWM)?

    IO_WDT_USE                => IO_WDT_USE,        -- implement watch dog timer (WDT)?

    IO_CLIC_USE               => IO_CLIC_USE,       -- implement core local interrupt controller (CLIC)?

    IO_TRNG_USE               => IO_TRNG_USE        -- implement true random number generator (TRNG)?

  )

  port map (

    -- global control --

    clk_i       => clk_i,        -- global clock, rising edge

    rstn_i      => sys_rstn,     -- global reset, low-active, async

    -- bus interface --

    bus_addr_o  => cpu_addr,     -- bus access address

    bus_rdata_i => cpu_rdata,    -- bus read data

    bus_wdata_o => cpu_wdata,    -- bus write data

    bus_ben_o   => cpu_ben,      -- byte enable

    bus_we_o    => cpu_we,       -- write enable

    bus_re_o    => cpu_re,       -- read enable

    bus_ack_i   => cpu_ack,      -- bus transfer acknowledge

    bus_err_i   => cpu_err,      -- bus transfer error

    -- external interrupts --

    clic_irq_i  => clic_irq,     -- CLIC interrupt request

    mtime_irq_i => mtime_irq     -- machine timer interrupt

  );

  -- CPU data input --

  cpu_rdata <= (imem_rdata or dmem_rdata or bootrom_rdata) or wishbone_rdata or (gpio_rdata or mtime_rdata or

               uart_rdata or spi_rdata or twi_rdata or pwm_rdata or wdt_rdata or clic_rdata or trng_rdata);

  -- CPU ACK input --

  cpu_ack <= (imem_ack or dmem_ack or bootrom_ack) or wishbone_ack or (gpio_ack or mtime_ack or

              uart_ack or spi_ack or twi_ack or pwm_ack or wdt_ack or clic_ack or trng_ack);

  -- CPU bus error input --

  cpu_err <= wishbone_err;

  -- Processor-Internal Instruction Memory (IMEM) -------------------------------------------

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

  neorv32_int_imem_inst_true:

  if (MEM_INT_IMEM_USE = true) generate

    neorv32_int_imem_inst: neorv32_imem

    generic map (

      IMEM_BASE      => MEM_ISPACE_BASE,   -- memory base address

      IMEM_SIZE      => MEM_INT_IMEM_SIZE, -- processor-internal instruction memory size in bytes

      IMEM_AS_ROM    => MEM_INT_IMEM_ROM,  -- implement IMEM as read-only memory?

      BOOTLOADER_USE => BOOTLOADER_USE     -- implement and use bootloader?

    )

    port map (

      clk_i  => clk_i,      -- global clock line

      rden_i => cpu_re,     -- read enable

      wren_i => cpu_we,     -- write enable

      ben_i  => cpu_ben,    -- byte write enable

      upen_i => '1',        -- update enable

      addr_i => cpu_addr,   -- address

      data_i => cpu_wdata,  -- data in

      data_o => imem_rdata, -- data out

      ack_o  => imem_ack    -- transfer acknowledge

    );

  end generate;

  neorv32_int_imem_inst_false:

  if (MEM_INT_IMEM_USE = false) generate

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

    imem_ack   <= '0';

  end generate;

  -- Processor-Internal Data Memory (DMEM) --------------------------------------------------

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

  neorv32_int_dmem_inst_true:

  if (MEM_INT_DMEM_USE = true) generate

    neorv32_int_dmem_inst: neorv32_dmem

    generic map (

      DMEM_BASE => MEM_DSPACE_BASE,  -- memory base address

      DMEM_SIZE => MEM_INT_DMEM_SIZE -- processor-internal data memory size in bytes

    )

    port map (

      clk_i  => clk_i,      -- global clock line

      rden_i => cpu_re,     -- read enable

      wren_i => cpu_we,     -- write enable

      ben_i  => cpu_ben,    -- byte write enable

      addr_i => cpu_addr,   -- address

      data_i => cpu_wdata,  -- data in

      data_o => dmem_rdata, -- data out

      ack_o  => dmem_ack    -- transfer acknowledge

    );

  end generate;

  neorv32_int_dmem_inst_false:

  if (MEM_INT_DMEM_USE = false) generate

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

    dmem_ack   <= '0';

  end generate;

  -- Processor-Internal Bootloader ROM (BOOTROM) --------------------------------------------

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

  neorv32_boot_rom_inst_true:

  if (BOOTLOADER_USE = true) generate

    neorv32_boot_rom_inst: neorv32_boot_rom

    port map (

      clk_i  => clk_i,         -- global clock line

      rden_i => cpu_re,        -- read enable

      addr_i => cpu_addr,      -- address

      data_o => bootrom_rdata, -- data out

      ack_o  => bootrom_ack    -- transfer acknowledge

    );

  end generate;

  neorv32_boot_rom_inst_false:

  if (BOOTLOADER_USE = false) generate

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

    bootrom_ack   <= '0';

  end generate;

  -- External Wishbone Gateway (WISHBONE) ---------------------------------------------------

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

  neorv32_wishbone_inst_true:

  if (MEM_EXT_USE = true) generate

    neorv32_wishbone_inst: neorv32_wishbone

    generic map (

      INTERFACE_REG_STAGES => MEM_EXT_REG_STAGES, -- number of interface register stages (0,1,2)

      -- Memory configuration: Instruction memory --

      MEM_ISPACE_BASE      => MEM_ISPACE_BASE,   -- base address of instruction memory space

      MEM_ISPACE_SIZE      => MEM_ISPACE_SIZE,   -- total size of instruction memory space in byte

      MEM_INT_IMEM_USE     => MEM_INT_IMEM_USE,  -- implement processor-internal instruction memory

      MEM_INT_IMEM_SIZE    => MEM_INT_IMEM_SIZE, -- size of processor-internal instruction memory in bytes

      -- Memory configuration: Data memory --

      MEM_DSPACE_BASE      => MEM_DSPACE_BASE,   -- base address of data memory space

      MEM_DSPACE_SIZE      => MEM_DSPACE_SIZE,   -- total size of data memory space in byte

      MEM_INT_DMEM_USE     => MEM_INT_DMEM_USE,  -- implement processor-internal data memory

      MEM_INT_DMEM_SIZE    => MEM_INT_DMEM_SIZE  -- size of processor-internal data memory in bytes

    )

    port map (

      -- global control --

      clk_i    => clk_i,          -- global clock line

      rstn_i   => sys_rstn,       -- global reset line, low-active

      -- host access --

      addr_i   => cpu_addr,       -- address

      rden_i   => cpu_re,         -- read enable

      wren_i   => cpu_we,         -- write enable

      ben_i    => cpu_ben,        -- byte write enable

      data_i   => cpu_wdata,      -- data in

      data_o   => wishbone_rdata, -- data out

      ack_o    => wishbone_ack,   -- transfer acknowledge

      err_o    => wishbone_err,   -- transfer error

      -- wishbone interface --

      wb_adr_o => wb_adr_o,       -- address

      wb_dat_i => wb_dat_i,       -- read data

      wb_dat_o => wb_dat_o,       -- write data

      wb_we_o  => wb_we_o,        -- read/write

      wb_sel_o => wb_sel_o,       -- byte enable

      wb_stb_o => wb_stb_o,       -- strobe

      wb_cyc_o => wb_cyc_o,       -- valid cycle

      wb_ack_i => wb_ack_i,       -- transfer acknowledge

      wb_err_i => wb_err_i        -- transfer error

    );

  end generate;

  neorv32_wishbone_inst_false:

  if (MEM_EXT_USE = false) generate

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

    wishbone_ack   <= '0';

    wishbone_err   <= '0';

    --

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

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

    wb_we_o  <= '0';

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

    wb_stb_o <= '0';

    wb_cyc_o <= '0';

  end generate;

  -- IO Access? -----------------------------------------------------------------------------

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

  io_acc  <= '1' when (cpu_addr(data_width_c-1 downto index_size_f(io_size_c)) = io_base_c(data_width_c-1 downto index_size_f(io_size_c))) else '0';

  io_rden <= io_acc and cpu_re;

  io_wren <= io_acc and cpu_we;

  -- General Purpose Input/Output Port (GPIO) -----------------------------------------------

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

  neorv32_gpio_inst_true:

  if (IO_GPIO_USE = true) generate

    neorv32_gpio_inst: neorv32_gpio

    port map (

      -- host access --

      clk_i  => clk_i,      -- global clock line

      addr_i => cpu_addr,   -- address

      rden_i => io_rden,    -- read enable

      wren_i => io_wren,    -- write enable

      ben_i  => cpu_ben,    -- byte write enable

      data_i => cpu_wdata,  -- data in

      data_o => gpio_rdata, -- data out

      ack_o  => gpio_ack,   -- transfer acknowledge

      -- parallel io --

      gpio_o => gpio_o,

      gpio_i => gpio_i,

      -- interrupt --

      irq_o  => gpio_irq    -- pin-change interrupt

    );

  end generate;

  neorv32_gpio_inst_false:

  if (IO_GPIO_USE = false) generate

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

    gpio_ack   <= '0';

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

    gpio_irq   <= '0';

  end generate;

  -- Core-Local Interrupt Controller (CLIC) -------------------------------------------------

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

  neorv32_clic_inst_true:

  if (IO_CLIC_USE = true) generate

    neorv32_clic_inst: neorv32_clic

    port map (

      -- host access --

      clk_i     => clk_i,      -- global clock line

      rden_i    => io_rden,    -- read enable

      wren_i    => io_wren,    -- write enable

      ben_i     => cpu_ben,    -- byte write enable

      addr_i    => cpu_addr,   -- address

      data_i    => cpu_wdata,  -- data in

      data_o    => clic_rdata, -- data out

      ack_o     => clic_ack,   -- transfer acknowledge

      -- cpu interrupt --

      cpu_irq_o => clic_irq,   -- trigger CPU's external IRQ

      -- external interrupt lines --

      ext_irq_i => clic_xirq,  -- IRQ, triggering on HIGH level

      ext_ack_o => clic_xack   -- acknowledge

    );

  end generate;

  -- CLIC interrupt channels and priority --

  clic_xirq(0) <= wdt_irq; -- highest priority

  clic_xirq(1) <= '0'; -- reserved

  clic_xirq(2) <= gpio_irq;

  clic_xirq(3) <= uart_irq;

  clic_xirq(4) <= spi_irq;

  clic_xirq(5) <= twi_irq;

  clic_xirq(6) <= ext_irq_i(0);

  clic_xirq(7) <= ext_irq_i(1); -- lowest priority

  ext_ack_o <= clic_xirq(7 downto 6); -- external interrupt request acknowledge

  neorv32_clic_inst_false:

  if (IO_CLIC_USE = false) generate

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

    clic_ack   <= '0';

    clic_irq   <= '0';

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

  end generate;

  -- Watch Dog Timer (WDT) ------------------------------------------------------------------

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

  neorv32_wdt_inst_true:

  if (IO_WDT_USE = true) generate

    neorv32_wdt_inst: neorv32_wdt

    port map (

      -- host access --

      clk_i       => clk_i,      -- global clock line

      rstn_i      => ext_rstn,   -- global reset line, low-active

      rden_i      => io_rden,    -- read enable

      wren_i      => io_wren,    -- write enable

      ben_i       => cpu_ben,    -- byte write enable

      addr_i      => cpu_addr,   -- address

      data_i      => cpu_wdata,  -- data in

      data_o      => wdt_rdata,  -- data out

      ack_o       => wdt_ack,    -- transfer acknowledge

      -- clock generator --

      clkgen_en_o => wdt_cg_en,  -- enable clock generator

      clkgen_i    => clk_gen,

      -- timeout event --

      irq_o       => wdt_irq,    -- timeout IRQ

      rstn_o      => wdt_rstn    -- timeout reset, low_active, use it as async!

    );

  end generate;

  neorv32_wdt_inst_false:

  if (IO_WDT_USE = false) generate

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

    wdt_ack   <= '0';

    wdt_irq   <= '0';

    wdt_rstn  <= '1';

    wdt_cg_en <= '0';

  end generate;

  -- Machine System Timer (MTIME) -----------------------------------------------------------

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

  neorv32_mtime_inst_true:

  if (IO_MTIME_USE = true) generate

    neorv32_mtime_inst: neorv32_mtime

    port map (

      -- host access --

      clk_i     => clk_i,        -- global clock line

      addr_i    => cpu_addr,     -- address

      rden_i    => io_rden,      -- read enable

      wren_i    => io_wren,      -- write enable

      ben_i     => cpu_ben,      -- byte write enable

      data_i    => cpu_wdata,    -- data in