Subversion Repositories neorv32

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

-- # << NEORV32 - CPU Top Entity >>                                                                #

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

-- # NEORV32 CPU:                                                                                  #

-- # * neorv32_cpu.vhd                  - CPU top entity                                           #

-- #   * neorv32_cpu_alu.vhd            - Arithmetic/logic unit                                    #

-- #   * neorv32_cpu_bus.vhd            - Instruction and data bus interface unit                  #

-- #   * neorv32_cpu_cp_muldiv.vhd      - MULDIV co-processor                                      #

-- #   * neorv32_cpu_ctrl.vhd           - CPU control and CSR system                               #

-- #     * neorv32_cpu_decompressor.vhd - Compressed instructions decoder                          #

-- #   * neorv32_cpu_regfile.vhd        - Data register file                                       #

-- #                                                                                               #

-- #   * neorv32_package.vhd            - Main CPU/processor package file                          #

-- #                                                                                               #

-- # Check out the processor's data sheet for more information: docs/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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-- # 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_cpu is

  generic (

    -- General --

    HW_THREAD_ID                 : std_ulogic_vector(31 downto 0):= (others => '0'); -- hardware thread id

    CPU_BOOT_ADDR                : std_ulogic_vector(31 downto 0):= (others => '0'); -- cpu boot address

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_A        : boolean := false; -- implement atomic extension?

    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_U        : boolean := false; -- implement user mode extension?

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

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

    -- Extension Options --

    FAST_MUL_EN                  : boolean := false; -- use DSPs for M extension's multiplier

    FAST_SHIFT_EN                : boolean := false; -- use barrel shifter for shift operations

    -- Physical Memory Protection (PMP) --

    PMP_USE                      : boolean := false  -- implement PMP?

  );

  port (

    -- global control --

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

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

    -- instruction bus interface --

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

    i_bus_rdata_i  : in  std_ulogic_vector(data_width_c-1 downto 0) := (others => '0'); -- bus read data

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

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

    i_bus_we_o     : out std_ulogic; -- write enable

    i_bus_re_o     : out std_ulogic; -- read enable

    i_bus_cancel_o : out std_ulogic; -- cancel current bus transaction

    i_bus_ack_i    : in  std_ulogic := '0'; -- bus transfer acknowledge

    i_bus_err_i    : in  std_ulogic := '0'; -- bus transfer error

    i_bus_fence_o  : out std_ulogic; -- executed FENCEI operation

    i_bus_priv_o   : out std_ulogic_vector(1 downto 0); -- privilege level

    i_bus_lock_o   : out std_ulogic; -- locked/exclusive access

    -- data bus interface --

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

    d_bus_rdata_i  : in  std_ulogic_vector(data_width_c-1 downto 0) := (others => '0'); -- bus read data

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

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

    d_bus_we_o     : out std_ulogic; -- write enable

    d_bus_re_o     : out std_ulogic; -- read enable

    d_bus_cancel_o : out std_ulogic; -- cancel current bus transaction

    d_bus_ack_i    : in  std_ulogic := '0'; -- bus transfer acknowledge

    d_bus_err_i    : in  std_ulogic := '0'; -- bus transfer error

    d_bus_fence_o  : out std_ulogic; -- executed FENCE operation

    d_bus_priv_o   : out std_ulogic_vector(1 downto 0); -- privilege level

    d_bus_lock_o   : out std_ulogic; -- locked/exclusive access

    -- system time input from MTIME --

    time_i         : in  std_ulogic_vector(63 downto 0) := (others => '0'); -- current system time

    -- interrupts (risc-v compliant) --

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

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

    mtime_irq_i    : in  std_ulogic := '0'; -- machine timer interrupt

    -- fast interrupts (custom) --

    firq_i         : in  std_ulogic_vector(3 downto 0) := (others => '0')

  );

end neorv32_cpu;

architecture neorv32_cpu_rtl of neorv32_cpu is

  -- local signals --

  signal ctrl       : std_ulogic_vector(ctrl_width_c-1 downto 0); -- main control bus

  signal alu_cmp    : std_ulogic_vector(1 downto 0); -- alu comparator result

  signal imm        : std_ulogic_vector(data_width_c-1 downto 0); -- immediate

  signal instr      : std_ulogic_vector(data_width_c-1 downto 0); -- new instruction

  signal rs1, rs2   : std_ulogic_vector(data_width_c-1 downto 0); -- source registers

  signal alu_opb    : std_ulogic_vector(data_width_c-1 downto 0); -- ALU operand b

  signal alu_res    : std_ulogic_vector(data_width_c-1 downto 0); -- alu result

  signal alu_add    : std_ulogic_vector(data_width_c-1 downto 0); -- alu address result

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

  signal alu_wait   : std_ulogic; -- alu is busy due to iterative unit

  signal bus_i_wait : std_ulogic; -- wait for current bus instruction fetch

  signal bus_d_wait : std_ulogic; -- wait for current bus data access

  signal csr_rdata  : std_ulogic_vector(data_width_c-1 downto 0); -- csr read data

  signal mar        : std_ulogic_vector(data_width_c-1 downto 0); -- current memory address register

  signal ma_instr   : std_ulogic; -- misaligned instruction address

  signal ma_load    : std_ulogic; -- misaligned load data address

  signal ma_store   : std_ulogic; -- misaligned store data address

  signal be_instr   : std_ulogic; -- bus error on instruction access

  signal be_load    : std_ulogic; -- bus error on load data access

  signal be_store   : std_ulogic; -- bus error on store data access

  signal fetch_pc   : std_ulogic_vector(data_width_c-1 downto 0); -- pc for instruction fetch

  signal curr_pc    : std_ulogic_vector(data_width_c-1 downto 0); -- current pc (for current executed instruction)

  -- co-processor interface --

  signal cp0_data,  cp1_data,  cp2_data,  cp3_data  : std_ulogic_vector(data_width_c-1 downto 0);

  signal cp0_valid, cp1_valid, cp2_valid, cp3_valid : std_ulogic;

  signal cp0_start, cp1_start, cp2_start, cp3_start : std_ulogic;

  -- pmp interface --

  signal pmp_addr  : pmp_addr_if_t;

  signal pmp_ctrl  : pmp_ctrl_if_t;

begin

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

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

  -- CSR system --

  assert not (CPU_EXTENSION_RISCV_Zicsr = false) report "NEORV32 CPU CONFIG WARNING! No exception/interrupt/trap/machine features available when CPU_EXTENSION_RISCV_Zicsr = false." severity warning;

  -- U-extension requires Zicsr extension --

  assert not ((CPU_EXTENSION_RISCV_Zicsr = false) and (CPU_EXTENSION_RISCV_U = true)) report "NEORV32 CPU CONFIG ERROR! User mode requires CPU_EXTENSION_RISCV_Zicsr extension." severity error;

  -- PMP requires Zicsr extension --

  assert not ((CPU_EXTENSION_RISCV_Zicsr = false) and (PMP_USE = true)) report "NEORV32 CPU CONFIG ERROR! Physical memory protection (PMP) requires CPU_EXTENSION_RISCV_Zicsr extension." severity error;

  -- RISC-V standard performance counters -

  assert not ((CPU_EXTENSION_RISCV_Zicsr = true) and (zicnt_en_c = false)) report "NEORV32 CPU CONFIG WARNING! Standard RISC-V peformance counters ([m]cycle[h], [m]instret[h]) will not be implemented (not RISC-V-compliant!)." severity warning;

  -- Instruction prefetch buffer size --

  assert not (is_power_of_two_f(ipb_entries_c) = false) report "NEORV32 CPU CONFIG ERROR! Number of entries in instruction prefetch buffer <ipb_entries_c> has to be a power of two." severity error;

  -- A extension - only lr.w and sc.w supported yet --

  assert not (CPU_EXTENSION_RISCV_A = true) report "NEORV32 CPU CONFIG WARNING! Atomic operations extension (A) only supports >lr.w< and >sc.w< instructions yet." severity warning;

  -- PMP regions check --

  assert not ((pmp_num_regions_c > pmp_max_r_c) and (PMP_USE = true)) report "NEORV32 CPU CONFIG ERROR! Number of PMP regions <pmp_num_regions_c> out of valid range." severity error;

  -- PMP granulartiy --

  assert not ((is_power_of_two_f(pmp_min_granularity_c) = false) and (PMP_USE = true)) report "NEORV32 CPU CONFIG ERROR! PMP granulartiy has to be a power of two." severity error;

  assert not ((pmp_min_granularity_c < 8) and (PMP_USE = true)) report "NEORV32 CPU CONFIG ERROR! PMP granulartiy has to be >= 8 bytes." severity error;

  -- PMP notifier --

  assert not (PMP_USE = true) report "NEORV32 CPU CONFIG NOTE: Implementing physical memory protection (PMP) with " & integer'image(pmp_num_regions_c) & " regions and " & integer'image(pmp_min_granularity_c) & " bytes minimal region size (granulartiy)." severity note;

  -- Control Unit ---------------------------------------------------------------------------

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

  neorv32_cpu_control_inst: neorv32_cpu_control

  generic map (

    -- General --

    HW_THREAD_ID                 => HW_THREAD_ID,  -- hardware thread id

    CPU_BOOT_ADDR                => CPU_BOOT_ADDR, -- cpu boot address

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_A        => CPU_EXTENSION_RISCV_A,        -- implement atomic extension?

    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_U        => CPU_EXTENSION_RISCV_U,        -- implement user mode extension?

    CPU_EXTENSION_RISCV_Zicsr    => CPU_EXTENSION_RISCV_Zicsr,    -- implement CSR system?

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

    -- Physical memory protection (PMP) --

    PMP_USE                      => PMP_USE        -- implement physical memory protection?

  )

  port map (

    -- global control --

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

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

    ctrl_o        => ctrl,        -- main control bus

    -- status input --

    alu_wait_i    => alu_wait,    -- wait for ALU

    bus_i_wait_i  => bus_i_wait,  -- wait for bus

    bus_d_wait_i  => bus_d_wait,  -- wait for bus

    -- data input --

    instr_i       => instr,       -- instruction

    cmp_i         => alu_cmp,     -- comparator status

    alu_add_i     => alu_add,     -- ALU address result

    rs1_i         => rs1,         -- rf source 1

    -- data output --

    imm_o         => imm,         -- immediate

    fetch_pc_o    => fetch_pc,    -- PC for instruction fetch

    curr_pc_o     => curr_pc,     -- current PC (corresponding to current instruction)

    csr_rdata_o   => csr_rdata,   -- CSR read data

    -- interrupts (risc-v compliant) --

    msw_irq_i     => msw_irq_i,   -- machine software interrupt

    mext_irq_i    => mext_irq_i,  -- machine external interrupt

    mtime_irq_i   => mtime_irq_i, -- machine timer interrupt

    -- fast interrupts (custom) --

    firq_i        => firq_i,

    -- system time input from MTIME --

    time_i        => time_i,      -- current system time

    -- physical memory protection --

    pmp_addr_o    => pmp_addr,    -- addresses

    pmp_ctrl_o    => pmp_ctrl,    -- configs

    -- bus access exceptions --

    mar_i         => mar,         -- memory address register

    ma_instr_i    => ma_instr,    -- misaligned instruction address

    ma_load_i     => ma_load,     -- misaligned load data address

    ma_store_i    => ma_store,    -- misaligned store data address

    be_instr_i    => be_instr,    -- bus error on instruction access

    be_load_i     => be_load,     -- bus error on load data access

    be_store_i    => be_store     -- bus error on store data access

  );

  -- Register File --------------------------------------------------------------------------

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

  neorv32_regfile_inst: neorv32_cpu_regfile

  generic map (

    CPU_EXTENSION_RISCV_E => CPU_EXTENSION_RISCV_E -- implement embedded RF extension?

  )

  port map (

    -- global control --

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

    ctrl_i => ctrl,               -- main control bus

    -- data input --

    mem_i  => rdata,              -- memory read data

    alu_i  => alu_res,            -- ALU result

    csr_i  => csr_rdata,          -- CSR read data

    -- data output --

    rs1_o  => rs1,                -- operand 1

    rs2_o  => rs2                 -- operand 2

  );

  -- ALU ------------------------------------------------------------------------------------

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

  neorv32_cpu_alu_inst: neorv32_cpu_alu

  generic map (

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

    FAST_SHIFT_EN         => FAST_SHIFT_EN          -- use barrel shifter for shift operations

  )

  port map (

    -- global control --

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

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

    ctrl_i      => ctrl,          -- main control bus

    -- data input --

    rs1_i       => rs1,           -- rf source 1

    rs2_i       => rs2,           -- rf source 2

    pc2_i       => curr_pc,       -- delayed PC

    imm_i       => imm,           -- immediate

    -- data output --

    cmp_o       => alu_cmp,       -- comparator status

    res_o       => alu_res,       -- ALU result

    add_o       => alu_add,       -- address computation result

    opb_o       => alu_opb,       -- ALU operand B

    -- co-processor interface --

    cp0_start_o => cp0_start,     -- trigger co-processor 0

    cp0_data_i  => cp0_data,      -- co-processor 0 result

    cp0_valid_i => cp0_valid,     -- co-processor 0 result valid

    cp1_start_o => cp1_start,     -- trigger co-processor 1

    cp1_data_i  => cp1_data,      -- co-processor 1 result

    cp1_valid_i => cp1_valid,     -- co-processor 1 result valid

    cp2_start_o => cp2_start,     -- trigger co-processor 2

    cp2_data_i  => cp2_data,      -- co-processor 2 result

    cp2_valid_i => cp2_valid,     -- co-processor 2 result valid

    cp3_start_o => cp3_start,     -- trigger co-processor 3

    cp3_data_i  => cp3_data,      -- co-processor 3 result

    cp3_valid_i => cp3_valid,     -- co-processor 3 result valid

    -- status --

    wait_o      => alu_wait       -- busy due to iterative processing units

  );

  -- Co-Processor 0: MULDIV Unit ------------------------------------------------------------

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

  neorv32_cpu_cp_muldiv_inst_true:

  if (CPU_EXTENSION_RISCV_M = true) generate

    neorv32_cpu_cp_muldiv_inst: neorv32_cpu_cp_muldiv

    generic map (

      FAST_MUL_EN => FAST_MUL_EN  -- use DSPs for faster multiplication

    )

    port map (

      -- global control --

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

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

      ctrl_i  => ctrl,            -- main control bus

      start_i => cp0_start,       -- trigger operation

      -- data input --

      rs1_i   => rs1,             -- rf source 1

      rs2_i   => rs2,             -- rf source 2

      -- result and status --

      res_o   => cp0_data,        -- operation result

      valid_o => cp0_valid        -- data output valid

    );

  end generate;

  neorv32_cpu_cp_muldiv_inst_false:

  if (CPU_EXTENSION_RISCV_M = false) generate

    cp0_data  <= (others => '0');

    cp0_valid <= cp0_start; -- to make sure CPU does not get stalled if there is an accidental access

  end generate;

  -- Co-Processor 1: Atomic Memory Access (SC - store-conditional) --------------------------

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

  atomic_op_cp: process(cp1_start, ctrl)

  begin

    -- "fake" co-processor for atomic operations

    -- used to get the result of a store-conditional operation into the data path

    if (CPU_EXTENSION_RISCV_A = true) then

      if (cp1_start = '1') then

        cp1_data    <= (others => '0');

        cp1_data(0) <= not ctrl(ctrl_bus_lock_c);

        cp1_valid   <= '1';

      else

        cp1_data  <= (others => '0');

        cp1_valid <= '0';

      end if;

    else

      cp1_data  <= (others => '0');

      cp1_valid <= cp1_start; -- to make sure CPU does not get stalled if there is an accidental access

    end if;

  end process atomic_op_cp;

  -- Co-Processor 2: Not implemented (yet) --------------------------------------------------

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

  -- control: ctrl cp2_start

  -- inputs:  rs1 rs2 alu_cmp alu_opb

  cp2_data  <= (others => '0');

  cp2_valid <= cp2_start; -- to make sure CPU does not get stalled if there is an accidental access

  -- Co-Processor 3: Not implemented (yet) --------------------------------------------------

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

  -- control: ctrl cp3_start

  -- inputs:  rs1 rs2 alu_cmp alu_opb

  cp3_data  <= (others => '0');

  cp3_valid <= cp3_start; -- to make sure CPU does not get stalled if there is an accidental access

  -- Bus Interface Unit ---------------------------------------------------------------------

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

  neorv32_cpu_bus_inst: neorv32_cpu_bus

  generic map (

    CPU_EXTENSION_RISCV_C => CPU_EXTENSION_RISCV_C, -- implement compressed extension?

    -- Physical memory protection (PMP) --

    PMP_USE               => PMP_USE                -- implement physical memory protection?

  )

  port map (

    -- global control --

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

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

    ctrl_i         => ctrl,           -- main control bus

    -- cpu instruction fetch interface --

    fetch_pc_i     => fetch_pc,       -- PC for instruction fetch

    instr_o        => instr,          -- instruction

    i_wait_o       => bus_i_wait,     -- wait for fetch to complete

    --

    ma_instr_o     => ma_instr,       -- misaligned instruction address

    be_instr_o     => be_instr,       -- bus error on instruction access

    -- cpu data access interface --

    addr_i         => alu_add,        -- ALU.add result -> access address

    wdata_i        => rs2,            -- write data

    rdata_o        => rdata,          -- read data

    mar_o          => mar,            -- current memory address register

    d_wait_o       => bus_d_wait,     -- wait for access to complete

    --

    ma_load_o      => ma_load,        -- misaligned load data address

    ma_store_o     => ma_store,       -- misaligned store data address

    be_load_o      => be_load,        -- bus error on load data access

    be_store_o     => be_store,       -- bus error on store data access

    -- physical memory protection --

    pmp_addr_i     => pmp_addr,       -- addresses

    pmp_ctrl_i     => pmp_ctrl,       -- configs

    -- instruction bus --

    i_bus_addr_o   => i_bus_addr_o,   -- bus access address

    i_bus_rdata_i  => i_bus_rdata_i,  -- bus read data

    i_bus_wdata_o  => i_bus_wdata_o,  -- bus write data

    i_bus_ben_o    => i_bus_ben_o,    -- byte enable

    i_bus_we_o     => i_bus_we_o,     -- write enable

    i_bus_re_o     => i_bus_re_o,     -- read enable

    i_bus_cancel_o => i_bus_cancel_o, -- cancel current bus transaction

    i_bus_ack_i    => i_bus_ack_i,    -- bus transfer acknowledge

    i_bus_err_i    => i_bus_err_i,    -- bus transfer error

    i_bus_fence_o  => i_bus_fence_o,  -- fence operation

    i_bus_lock_o   => i_bus_lock_o,   -- locked/exclusive access

    -- data bus --

    d_bus_addr_o   => d_bus_addr_o,   -- bus access address

    d_bus_rdata_i  => d_bus_rdata_i,  -- bus read data

    d_bus_wdata_o  => d_bus_wdata_o,  -- bus write data

    d_bus_ben_o    => d_bus_ben_o,    -- byte enable

    d_bus_we_o     => d_bus_we_o,     -- write enable

    d_bus_re_o     => d_bus_re_o,     -- read enable

    d_bus_cancel_o => d_bus_cancel_o, -- cancel current bus transaction

    d_bus_ack_i    => d_bus_ack_i,    -- bus transfer acknowledge

    d_bus_err_i    => d_bus_err_i,    -- bus transfer error

    d_bus_fence_o  => d_bus_fence_o,  -- fence operation

    d_bus_lock_o   => d_bus_lock_o    -- locked/exclusive access

  );

  -- current privilege level --

  i_bus_priv_o <= ctrl(ctrl_priv_lvl_msb_c downto ctrl_priv_lvl_lsb_c);

  d_bus_priv_o <= ctrl(ctrl_priv_lvl_msb_c downto ctrl_priv_lvl_lsb_c);

end neorv32_cpu_rtl;