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

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

    CSR_COUNTERS_USE             : boolean := true;   -- implement RISC-V perf. counters ([m]instret[h], [m]cycle[h], time[h])?

    USER_CODE                    : std_ulogic_vector(31 downto 0) := x"00000000"; -- custom user code

    -- 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?

    CPU_EXTENSION_RISCV_Zifencei : boolean := true;   -- implement instruction stream sync.?

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

    IO_DEVNULL_USE               : boolean := true    -- implement dummy device (DEVNULL)?

  );

  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

    -- Advanced memory control signals (available if MEM_EXT_USE = true) --

    fence_o    : out std_ulogic; -- indicates an executed FENCE operation

    fencei_o   : out std_ulogic; -- indicates an executed FENCEI operation

    -- 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_sck_o  : out std_ulogic; -- SPI serial clock

    spi_sdo_o  : out std_ulogic; -- controller data out, peripheral data in

    spi_sdi_i  : in  std_ulogic := '0'; -- controller data in, peripheral data out

    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 --

    msw_irq_i  : in  std_ulogic := '0'; -- machine software interrupt

    mext_irq_i : in  std_ulogic := '0'  -- machine external interrupt

  );

end neorv32_top;

architecture neorv32_top_rtl of neorv32_top is

  -- CPU boot address --

  constant boot_addr_c : std_ulogic_vector(31 downto 0) := cond_sel_stdulogicvector_f(BOOTLOADER_USE, boot_base_c, MEM_ISPACE_BASE);

  -- 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;

  -- bus interface --

  type bus_interface_t is record

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

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

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

    ben    : std_ulogic_vector(03 downto 0); -- byte enable

    we     : std_ulogic; -- write enable

    re     : std_ulogic; -- read enable

    cancel : std_ulogic; -- cancel current transfer

    ack    : std_ulogic; -- bus transfer acknowledge

    err    : std_ulogic; -- bus transfer error

    fence  : std_ulogic; -- fence(i) instruction executed

  end record;

  signal cpu_i, cpu_d, p_bus : bus_interface_t;

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

  signal trng_ack       : std_ulogic;

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

  signal devnull_ack    : std_ulogic;

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

  signal sysinfo_ack    : std_ulogic;

  -- IRQs --

  signal mtime_irq : std_ulogic;

  signal fast_irq  : std_ulogic_vector(3 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;

  -- misc --

  signal mtime_time : std_ulogic_vector(63 downto 0); -- current system time from MTIME

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 --

      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. Processor-internal components have 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 features available when CPU_EXTENSION_RISCV_Zicsr = false." severity warning;

      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 software framwork." 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 software framwork." 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 --

    CSR_COUNTERS_USE             => CSR_COUNTERS_USE, -- implement RISC-V perf. counters ([m]instret[h], [m]cycle[h], time[h])?

    HW_THREAD_ID                 => (others => '0'),  -- hardware thread id

    CPU_BOOT_ADDR                => boot_addr_c,      -- cpu boot address

    -- 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?

    CPU_EXTENSION_RISCV_Zifencei => CPU_EXTENSION_RISCV_Zifencei, -- implement instruction stream sync.?

    -- Bus Interface --

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

  )

  port map (

    -- global control --

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

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

    -- instruction bus interface --

    i_bus_addr_o   => cpu_i.addr,   -- bus access address

    i_bus_rdata_i  => cpu_i.rdata,  -- bus read data

    i_bus_wdata_o  => cpu_i.wdata,  -- bus write data

    i_bus_ben_o    => cpu_i.ben,    -- byte enable

    i_bus_we_o     => cpu_i.we,     -- write enable

    i_bus_re_o     => cpu_i.re,     -- read enable

    i_bus_cancel_o => cpu_i.cancel, -- cancel current bus transaction

    i_bus_ack_i    => cpu_i.ack,    -- bus transfer acknowledge

    i_bus_err_i    => cpu_i.err,    -- bus transfer error

    i_bus_fence_o  => cpu_i.fence,  -- executed FENCEI operation

    -- data bus interface --

    d_bus_addr_o   => cpu_d.addr,   -- bus access address

    d_bus_rdata_i  => cpu_d.rdata,  -- bus read data

    d_bus_wdata_o  => cpu_d.wdata,  -- bus write data

    d_bus_ben_o    => cpu_d.ben,    -- byte enable

    d_bus_we_o     => cpu_d.we,     -- write enable

    d_bus_re_o     => cpu_d.re,     -- read enable

    d_bus_cancel_o => cpu_d.cancel, -- cancel current bus transaction

    d_bus_ack_i    => cpu_d.ack,    -- bus transfer acknowledge

    d_bus_err_i    => cpu_d.err,    -- bus transfer error

    d_bus_fence_o  => cpu_d.fence,  -- executed FENCE operation

    -- system time input from MTIME --

    time_i         => mtime_time,   -- current system time

    -- interrupts (risc-v compliant) --

    msw_irq_i      => msw_irq_i,    -- machine software interrupt

    mext_irq_i     => mext_irq_i,   -- machine external interrupt request

    mtime_irq_i    => mtime_irq,    -- machine timer interrupt

    -- fast interrupts (custom) --

    firq_i         => fast_irq

  );

  -- advanced memory control --

  fence_o  <= cpu_d.fence; -- indicates an executed FENCE operation

  fencei_o <= cpu_i.fence; -- indicates an executed FENCEI operation

  -- fast interrupts --

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

  fast_irq(1) <= gpio_irq;

  fast_irq(2) <= uart_irq;

  fast_irq(3) <= spi_irq or twi_irq; -- lowest priority, can be triggered by SPI or TWI

  -- CPU Crossbar Switch --------------------------------------------------------------------

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

  neorv32_busswitch_inst: neorv32_busswitch

  generic map (

    PORT_CA_READ_ONLY => false, -- set if controller port A is read-only

    PORT_CB_READ_ONLY => true   -- set if controller port B is read-only

  )

  port map (

    -- global control --

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

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

    -- controller interface a --

    ca_bus_addr_i   => cpu_d.addr,   -- bus access address

    ca_bus_rdata_o  => cpu_d.rdata,  -- bus read data

    ca_bus_wdata_i  => cpu_d.wdata,  -- bus write data

    ca_bus_ben_i    => cpu_d.ben,    -- byte enable

    ca_bus_we_i     => cpu_d.we,     -- write enable

    ca_bus_re_i     => cpu_d.re,     -- read enable

    ca_bus_cancel_i => cpu_d.cancel, -- cancel current bus transaction

    ca_bus_ack_o    => cpu_d.ack,    -- bus transfer acknowledge

    ca_bus_err_o    => cpu_d.err,    -- bus transfer error

    -- controller interface b --

    cb_bus_addr_i   => cpu_i.addr,   -- bus access address

    cb_bus_rdata_o  => cpu_i.rdata,  -- bus read data

    cb_bus_wdata_i  => cpu_i.wdata,  -- bus write data

    cb_bus_ben_i    => cpu_i.ben,    -- byte enable

    cb_bus_we_i     => cpu_i.we,     -- write enable

    cb_bus_re_i     => cpu_i.re,     -- read enable

    cb_bus_cancel_i => cpu_i.cancel, -- cancel current bus transaction

    cb_bus_ack_o    => cpu_i.ack,    -- bus transfer acknowledge

    cb_bus_err_o    => cpu_i.err,    -- bus transfer error

    -- peripheral bus --

    p_bus_addr_o    => p_bus.addr,   -- bus access address

    p_bus_rdata_i   => p_bus.rdata,  -- bus read data

    p_bus_wdata_o   => p_bus.wdata,  -- bus write data

    p_bus_ben_o     => p_bus.ben,    -- byte enable

    p_bus_we_o      => p_bus.we,     -- write enable

    p_bus_re_o      => p_bus.re,     -- read enable

    p_bus_cancel_o  => p_bus.cancel, -- cancel current bus transaction

    p_bus_ack_i     => p_bus.ack,    -- bus transfer acknowledge

    p_bus_err_i     => p_bus.err     -- bus transfer error

  );

  -- processor bus: CPU data input --

  p_bus.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 trng_rdata or devnull_rdata or sysinfo_rdata);

  -- processor bus: CPU data ACK input --

  p_bus.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 trng_ack or devnull_ack or sysinfo_ack);

  -- processor bus: CPU data bus error input --

  p_bus.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 => p_bus.re,    -- read enable

      wren_i => p_bus.we,    -- write enable

      ben_i  => p_bus.ben,   -- byte write enable

      upen_i => '1',         -- update enable

      addr_i => p_bus.addr,  -- address

      data_i => p_bus.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 => p_bus.re,    -- read enable

      wren_i => p_bus.we,    -- write enable

      ben_i  => p_bus.ben,   -- byte write enable

      addr_i => p_bus.addr,  -- address

      data_i => p_bus.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 => p_bus.re,      -- read enable

      addr_i => p_bus.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   => p_bus.addr,     -- address

      rden_i   => p_bus.re,       -- read enable

      wren_i   => p_bus.we,       -- write enable

      ben_i    => p_bus.ben,      -- byte write enable

      data_i   => p_bus.wdata,    -- data in

      data_o   => wishbone_rdata, -- data out

      cancel_i => p_bus.cancel,   -- cancel current transaction

      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 (p_bus.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 p_bus.re;

  io_wren <= io_acc and p_bus.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 => p_bus.addr,  -- address

      rden_i => io_rden,     -- read enable

      wren_i => io_wren,     -- write enable

      ben_i  => p_bus.ben,   -- byte write enable

      data_i => p_bus.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;

  -- 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       => p_bus.ben,   -- byte write enable

      addr_i      => p_bus.addr,  -- address

      data_i      => p_bus.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