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

-- # << NEORV32 - System/Processor Configuration Information Memory (SYSINFO) >>                   #

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

-- # This unit provides information regarding the NEORV32 processor system configuration -         #

-- # mostly derived from the top's configuration generics.                                         #

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

-- # BSD 3-Clause License                                                                          #

-- #                                                                                               #

-- # Copyright (c) 2022, 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               #

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

-- # 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_sysinfo is

  generic (

    -- General --

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

    INT_BOOTLOADER_EN            : boolean; -- boot configuration: true = boot explicit bootloader; false = boot from int/ext (I)MEM

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_Zfinx    : boolean; -- implement 32-bit floating-point extension (using INT reg!)

    CPU_EXTENSION_RISCV_Zicsr    : boolean; -- implement CSR system?

    CPU_EXTENSION_RISCV_Zicntr   : boolean; -- implement base counters?

    CPU_EXTENSION_RISCV_Zihpm    : boolean; -- implement hardware performance monitors?

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

    CPU_EXTENSION_RISCV_Zmmul    : boolean; -- implement multiply-only M sub-extension?

    CPU_EXTENSION_RISCV_DEBUG    : boolean; -- implement CPU debug mode?

    -- Extension Options --

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

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

    CPU_CNT_WIDTH                : natural; -- total width of CPU cycle and instret counters (0..64)

    -- Physical memory protection (PMP) --

    PMP_NUM_REGIONS              : natural; -- number of regions (0..64)

    -- Internal Instruction memory --

    MEM_INT_IMEM_EN              : boolean; -- implement processor-internal instruction memory

    MEM_INT_IMEM_SIZE            : natural; -- size of processor-internal instruction memory in bytes

    -- Internal Data memory --

    MEM_INT_DMEM_EN              : boolean; -- implement processor-internal data memory

    MEM_INT_DMEM_SIZE            : natural; -- size of processor-internal data memory in bytes

    -- Internal Cache memory --

    ICACHE_EN                    : boolean; -- implement instruction cache

    ICACHE_NUM_BLOCKS            : natural; -- i-cache: number of blocks (min 2), has to be a power of 2

    ICACHE_BLOCK_SIZE            : natural; -- i-cache: block size in bytes (min 4), has to be a power of 2

    ICACHE_ASSOCIATIVITY         : natural; -- i-cache: associativity (min 1), has to be a power 2

    -- External memory interface --

    MEM_EXT_EN                   : boolean; -- implement external memory bus interface?

    MEM_EXT_BIG_ENDIAN           : boolean; -- byte order: true=big-endian, false=little-endian

    -- On-Chip Debugger --

    ON_CHIP_DEBUGGER_EN          : boolean; -- implement OCD?

    -- Processor peripherals --

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

    IO_MTIME_EN                  : boolean; -- implement machine system timer (MTIME)?

    IO_UART0_EN                  : boolean; -- implement primary universal asynchronous receiver/transmitter (UART0)?

    IO_UART1_EN                  : boolean; -- implement secondary universal asynchronous receiver/transmitter (UART1)?

    IO_SPI_EN                    : boolean; -- implement serial peripheral interface (SPI)?

    IO_TWI_EN                    : boolean; -- implement two-wire interface (TWI)?

    IO_PWM_NUM_CH                : natural; -- number of PWM channels to implement

    IO_WDT_EN                    : boolean; -- implement watch dog timer (WDT)?

    IO_TRNG_EN                   : boolean; -- implement true random number generator (TRNG)?

    IO_CFS_EN                    : boolean; -- implement custom functions subsystem (CFS)?

    IO_SLINK_EN                  : boolean; -- implement stream link interface?

    IO_NEOLED_EN                 : boolean; -- implement NeoPixel-compatible smart LED interface (NEOLED)?

    IO_XIRQ_NUM_CH               : natural; -- number of external interrupt (XIRQ) channels to implement

    IO_GPTMR_EN                  : boolean; -- implement general purpose timer (GPTMR)?

    IO_XIP_EN                    : boolean  -- implement execute in place module (XIP)?

  );

  port (

    -- host access --

    clk_i  : in  std_ulogic; -- global clock line

    addr_i : in  std_ulogic_vector(31 downto 0); -- address

    rden_i : in  std_ulogic; -- read enable

    wren_i : in  std_ulogic; -- write enable

    data_o : out std_ulogic_vector(31 downto 0); -- data out

    ack_o  : out std_ulogic; -- transfer acknowledge

    err_o  : out std_ulogic  -- transfer error

  );

end neorv32_sysinfo;

architecture neorv32_sysinfo_rtl of neorv32_sysinfo is

  -- IO space: module base address --

  constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit

  constant lo_abb_c : natural := index_size_f(sysinfo_size_c); -- low address boundary bit

  -- access control --

  signal acc_en : std_ulogic; -- module access enable

  signal rden   : std_ulogic;

  signal wren   : std_ulogic;

  signal iaddr  : std_ulogic_vector(02 downto 0);

  -- system information ROM --

  type info_mem_t is array (0 to 7) of std_ulogic_vector(31 downto 0);

  signal sysinfo_mem : info_mem_t;

begin

  -- Access Control -------------------------------------------------------------------------

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

  acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = sysinfo_base_c(hi_abb_c downto lo_abb_c)) else '0';

  rden   <= acc_en and rden_i; -- read access

  wren   <= acc_en and wren_i; -- write access

  iaddr  <= addr_i(index_size_f(sysinfo_size_c)-1 downto 2);

  -- Construct Info ROM ---------------------------------------------------------------------

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

  -- SYSINFO(0): Processor (primary) clock frequency --

  sysinfo_mem(0) <= std_ulogic_vector(to_unsigned(CLOCK_FREQUENCY, 32));

  -- SYSINFO(1): CPU configuration --

  sysinfo_mem(1)(00) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zicsr);    -- Zicsr

  sysinfo_mem(1)(01) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zifencei); -- Zifencei

  sysinfo_mem(1)(02) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zmmul);    -- Zmmul

  --

  sysinfo_mem(1)(04 downto 03) <= (others => '0'); -- reserved

  --

  sysinfo_mem(1)(05) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zfinx);    -- Zfinx ("F-alternative")

  sysinfo_mem(1)(06) <= bool_to_ulogic_f(boolean(CPU_CNT_WIDTH /= 64)); -- reduced-size CPU counters (Zxscnt)

  sysinfo_mem(1)(07) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zicntr);   -- base CPU counter

  sysinfo_mem(1)(08) <= bool_to_ulogic_f(boolean(PMP_NUM_REGIONS > 0)); -- PMP (physical memory protection)

  sysinfo_mem(1)(09) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_Zihpm);    -- HPM (hardware performance monitors)

  sysinfo_mem(1)(10) <= bool_to_ulogic_f(CPU_EXTENSION_RISCV_DEBUG);    -- RISC-V debug mode

  --

  sysinfo_mem(1)(29 downto 11) <= (others => '0'); -- reserved

  -- misc --

  sysinfo_mem(1)(30) <= bool_to_ulogic_f(FAST_MUL_EN);                  -- DSP-based multiplication (M extension only)

  sysinfo_mem(1)(31) <= bool_to_ulogic_f(FAST_SHIFT_EN);                -- parallel logic for shifts (like barrel shifters)

  -- SYSINFO(2): Implemented processor devices/features --

  -- Memory --

  sysinfo_mem(2)(00) <= bool_to_ulogic_f(INT_BOOTLOADER_EN); -- processor-internal bootloader implemented?

  sysinfo_mem(2)(01) <= bool_to_ulogic_f(MEM_EXT_EN);        -- external memory bus interface implemented?

  sysinfo_mem(2)(02) <= bool_to_ulogic_f(MEM_INT_IMEM_EN) and bool_to_ulogic_f(boolean(MEM_INT_IMEM_SIZE > 0)); -- processor-internal instruction memory implemented?

  sysinfo_mem(2)(03) <= bool_to_ulogic_f(MEM_INT_DMEM_EN) and bool_to_ulogic_f(boolean(MEM_INT_DMEM_SIZE > 0)); -- processor-internal data memory implemented?

  sysinfo_mem(2)(04) <= bool_to_ulogic_f(MEM_EXT_BIG_ENDIAN); -- is external memory bus interface using BIG-endian byte-order?

  sysinfo_mem(2)(05) <= bool_to_ulogic_f(ICACHE_EN);         -- processor-internal instruction cache implemented?

  --

  sysinfo_mem(2)(12 downto 06) <= (others => '0'); -- reserved

  -- Misc --

  sysinfo_mem(2)(13) <= bool_to_ulogic_f(is_simulation_c);     -- is this a simulation?

  sysinfo_mem(2)(14) <= bool_to_ulogic_f(ON_CHIP_DEBUGGER_EN); -- on-chip debugger implemented?

  sysinfo_mem(2)(15) <= bool_to_ulogic_f(dedicated_reset_c);   -- dedicated hardware reset of all core registers?

  -- IO --

  sysinfo_mem(2)(16) <= bool_to_ulogic_f(IO_GPIO_EN);   -- general purpose input/output port unit (GPIO) implemented?

  sysinfo_mem(2)(17) <= bool_to_ulogic_f(IO_MTIME_EN);  -- machine system timer (MTIME) implemented?

  sysinfo_mem(2)(18) <= bool_to_ulogic_f(IO_UART0_EN);  -- primary universal asynchronous receiver/transmitter (UART0) implemented?

  sysinfo_mem(2)(19) <= bool_to_ulogic_f(IO_SPI_EN);    -- serial peripheral interface (SPI) implemented?

  sysinfo_mem(2)(20) <= bool_to_ulogic_f(IO_TWI_EN);    -- two-wire interface (TWI) implemented?

  sysinfo_mem(2)(21) <= bool_to_ulogic_f(boolean(IO_PWM_NUM_CH > 0)); -- pulse-width modulation unit (PWM) implemented?

  sysinfo_mem(2)(22) <= bool_to_ulogic_f(IO_WDT_EN);    -- watch dog timer (WDT) implemented?

  sysinfo_mem(2)(23) <= bool_to_ulogic_f(IO_CFS_EN);    -- custom functions subsystem (CFS) implemented?

  sysinfo_mem(2)(24) <= bool_to_ulogic_f(IO_TRNG_EN);   -- true random number generator (TRNG) implemented?

  sysinfo_mem(2)(25) <= bool_to_ulogic_f(IO_SLINK_EN);  -- stream links (SLINK) implemented?

  sysinfo_mem(2)(26) <= bool_to_ulogic_f(IO_UART1_EN);  -- secondary universal asynchronous receiver/transmitter (UART1) implemented?

  sysinfo_mem(2)(27) <= bool_to_ulogic_f(IO_NEOLED_EN); -- NeoPixel-compatible smart LED interface (NEOLED) implemented?

  sysinfo_mem(2)(28) <= bool_to_ulogic_f(boolean(IO_XIRQ_NUM_CH > 0)); -- external interrupt controller (XIRQ) implemented?

  sysinfo_mem(2)(29) <= bool_to_ulogic_f(IO_GPTMR_EN);  -- general purpose timer (GPTMR) implemented?

  sysinfo_mem(2)(30) <= bool_to_ulogic_f(IO_XIP_EN);    -- execute in place module (XIP) implemented?

  --

  sysinfo_mem(2)(31) <= '0'; -- reserved

  -- SYSINFO(3): Cache configuration --

  sysinfo_mem(3)(03 downto 00) <= std_ulogic_vector(to_unsigned(index_size_f(ICACHE_BLOCK_SIZE),    4)) when (ICACHE_EN = true) else (others => '0'); -- i-cache: log2(block_size_in_bytes)

  sysinfo_mem(3)(07 downto 04) <= std_ulogic_vector(to_unsigned(index_size_f(ICACHE_NUM_BLOCKS),    4)) when (ICACHE_EN = true) else (others => '0'); -- i-cache: log2(number_of_block)

  sysinfo_mem(3)(11 downto 08) <= std_ulogic_vector(to_unsigned(index_size_f(ICACHE_ASSOCIATIVITY), 4)) when (ICACHE_EN = true) else (others => '0'); -- i-cache: log2(associativity)

  sysinfo_mem(3)(15 downto 12) <= "0001" when (ICACHE_ASSOCIATIVITY > 1) and (ICACHE_EN = true) else (others => '0'); -- i-cache: replacement strategy (LRU only (yet))

  --

  sysinfo_mem(3)(19 downto 16) <= (others => '0'); -- reserved - d-cache: log2(block_size)

  sysinfo_mem(3)(23 downto 20) <= (others => '0'); -- reserved - d-cache: log2(num_blocks)

  sysinfo_mem(3)(27 downto 24) <= (others => '0'); -- reserved - d-cache: log2(associativity)

  sysinfo_mem(3)(31 downto 28) <= (others => '0'); -- reserved - d-cache: replacement strategy

  -- SYSINFO(4): Base address of instruction memory space --

  sysinfo_mem(4) <= ispace_base_c; -- defined in neorv32_package.vhd file

  -- SYSINFO(5): Base address of data memory space --

  sysinfo_mem(5) <= dspace_base_c; -- defined in neorv32_package.vhd file

  -- SYSINFO(6): Size of IMEM in bytes --

  sysinfo_mem(6) <= std_ulogic_vector(to_unsigned(MEM_INT_IMEM_SIZE, 32)) when (MEM_INT_IMEM_EN = true) else (others => '0');

  -- SYSINFO(7): Size of DMEM in bytes --

  sysinfo_mem(7) <= std_ulogic_vector(to_unsigned(MEM_INT_DMEM_SIZE, 32)) when (MEM_INT_DMEM_EN = true) else (others => '0');

  -- Read Access ----------------------------------------------------------------------------

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

  read_access: process(clk_i)

  begin

    if rising_edge(clk_i) then

      ack_o  <= rden;

      err_o  <= wren;

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

      if (rden = '1') then

        data_o <= sysinfo_mem(to_integer(unsigned(iaddr)));

      end if;

    end if;

  end process read_access;

end neorv32_sysinfo_rtl;