Subversion Repositories neorv32

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

-- # << The NEORV32 RISC-V Processor - Top Entity >>                                               #

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

-- # Check out the processor's online documentation for more information:                          #

-- #  HQ:         https://github.com/stnolting/neorv32                                             #

-- #  Data Sheet: https://stnolting.github.io/neorv32                                              #

-- #  User Guide: https://stnolting.github.io/neorv32/ug                                           #

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

-- # 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:                                     #

-- #                                                                                               #

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-- #    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.                                                            #

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-- #    permission.                                                                                #

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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_top is

  generic (

    -- General --

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

    HW_THREAD_ID                 : natural := 0;      -- hardware thread id (32-bit)

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

    -- On-Chip Debugger (OCD) --

    ON_CHIP_DEBUGGER_EN          : boolean := false;  -- implement on-chip debugger

    -- RISC-V CPU Extensions --

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

    CPU_EXTENSION_RISCV_B        : boolean := false;  -- implement bit-manipulation 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 mul/div extension?

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

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

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

    CPU_EXTENSION_RISCV_Zicntr   : boolean := true;   -- implement base counters?

    CPU_EXTENSION_RISCV_Zihpm    : boolean := false;  -- implement hardware performance monitors?

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

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

    CPU_EXTENSION_RISCV_Zxcfu    : boolean := false;  -- implement custom (instr.) functions unit?

    -- Tuning Options --

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

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

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

    CPU_IPB_ENTRIES              : natural := 2;      -- entries is instruction prefetch buffer, has to be a power of 2

    -- Physical Memory Protection (PMP) --

    PMP_NUM_REGIONS              : natural := 0;      -- number of regions (0..16)

    PMP_MIN_GRANULARITY          : natural := 4;      -- minimal region granularity in bytes, has to be a power of 2, min 4 bytes

    -- Hardware Performance Monitors (HPM) --

    HPM_NUM_CNTS                 : natural := 0;      -- number of implemented HPM counters (0..29)

    HPM_CNT_WIDTH                : natural := 40;     -- total size of HPM counters (0..64)

    -- Internal Instruction memory (IMEM) --

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

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

    -- Internal Data memory (DMEM) --

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

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

    -- Internal Instruction Cache (iCACHE) --

    ICACHE_EN                    : boolean := false;  -- implement instruction cache

    ICACHE_NUM_BLOCKS            : natural := 4;      -- i-cache: number of blocks (min 1), has to be a power of 2

    ICACHE_BLOCK_SIZE            : natural := 64;     -- i-cache: block size in bytes (min 4), has to be a power of 2

    ICACHE_ASSOCIATIVITY         : natural := 1;      -- i-cache: associativity / number of sets (1=direct_mapped), has to be a power of 2

    -- External memory interface (WISHBONE) --

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

    MEM_EXT_TIMEOUT              : natural := 255;    -- cycles after a pending bus access auto-terminates (0 = disabled)

    MEM_EXT_PIPE_MODE            : boolean := false;  -- protocol: false=classic/standard wishbone mode, true=pipelined wishbone mode

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

    MEM_EXT_ASYNC_RX             : boolean := false;  -- use register buffer for RX data when false

    -- Stream link interface (SLINK) --

    SLINK_NUM_TX                 : natural := 0;      -- number of TX links (0..8)

    SLINK_NUM_RX                 : natural := 0;      -- number of TX links (0..8)

    SLINK_TX_FIFO                : natural := 1;      -- TX fifo depth, has to be a power of two

    SLINK_RX_FIFO                : natural := 1;      -- RX fifo depth, has to be a power of two

    -- External Interrupts Controller (XIRQ) --

    XIRQ_NUM_CH                  : natural := 0;      -- number of external IRQ channels (0..32)

    XIRQ_TRIGGER_TYPE            : std_ulogic_vector(31 downto 0) := x"ffffffff"; -- trigger type: 0=level, 1=edge

    XIRQ_TRIGGER_POLARITY        : std_ulogic_vector(31 downto 0) := x"ffffffff"; -- trigger polarity: 0=low-level/falling-edge, 1=high-level/rising-edge

    -- Processor peripherals --

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

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

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

    IO_UART0_RX_FIFO             : natural := 1;      -- RX fifo depth, has to be a power of two, min 1

    IO_UART0_TX_FIFO             : natural := 1;      -- TX fifo depth, has to be a power of two, min 1

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

    IO_UART1_RX_FIFO             : natural := 1;      -- RX fifo depth, has to be a power of two, min 1

    IO_UART1_TX_FIFO             : natural := 1;      -- TX fifo depth, has to be a power of two, min 1

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

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

    IO_PWM_NUM_CH                : natural := 0;      -- number of PWM channels to implement (0..60); 0 = disabled

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

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

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

    IO_CFS_CONFIG                : std_ulogic_vector(31 downto 0) := x"00000000"; -- custom CFS configuration generic

    IO_CFS_IN_SIZE               : positive := 32;    -- size of CFS input conduit in bits

    IO_CFS_OUT_SIZE              : positive := 32;    -- size of CFS output conduit in bits

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

    IO_NEOLED_TX_FIFO            : natural := 1;      -- NEOLED TX FIFO depth, 1..32k, has to be a power of two

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

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

  );

  port (

    -- Global control --

    clk_i          : in  std_ulogic; -- global clock, rising edge

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

    -- JTAG on-chip debugger interface (available if ON_CHIP_DEBUGGER_EN = true) --

    jtag_trst_i    : in  std_ulogic := 'U'; -- low-active TAP reset (optional)

    jtag_tck_i     : in  std_ulogic := 'U'; -- serial clock

    jtag_tdi_i     : in  std_ulogic := 'U'; -- serial data input

    jtag_tdo_o     : out std_ulogic;        -- serial data output

    jtag_tms_i     : in  std_ulogic := 'U'; -- mode select

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

    wb_tag_o       : out std_ulogic_vector(02 downto 0); -- request tag

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

    wb_dat_i       : in  std_ulogic_vector(31 downto 0) := (others => 'U'); -- 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_lock_o      : out std_ulogic; -- exclusive access request

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

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

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

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

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

    -- XIP (execute in place via SPI) signals (available if IO_XIP_EN = true) --

    xip_csn_o      : out std_ulogic; -- chip-select, low-active

    xip_clk_o      : out std_ulogic; -- serial clock

    xip_sdi_i      : in  std_ulogic := 'L'; -- device data input

    xip_sdo_o      : out std_ulogic; -- controller data output

    -- TX stream interfaces (available if SLINK_NUM_TX > 0) --

    slink_tx_dat_o : out sdata_8x32_t; -- output data

    slink_tx_val_o : out std_ulogic_vector(7 downto 0); -- valid output

    slink_tx_rdy_i : in  std_ulogic_vector(7 downto 0) := (others => 'L'); -- ready to send

    -- RX stream interfaces (available if SLINK_NUM_RX > 0) --

    slink_rx_dat_i : in  sdata_8x32_t := (others => (others => 'U')); -- input data

    slink_rx_val_i : in  std_ulogic_vector(7 downto 0) := (others => 'L'); -- valid input

    slink_rx_rdy_o : out std_ulogic_vector(7 downto 0); -- ready to receive

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

    gpio_o         : out std_ulogic_vector(63 downto 0); -- parallel output

    gpio_i         : in  std_ulogic_vector(63 downto 0) := (others => 'U'); -- parallel input

    -- primary UART0 (available if IO_UART0_EN = true) --

    uart0_txd_o    : out std_ulogic; -- UART0 send data

    uart0_rxd_i    : in  std_ulogic := 'U'; -- UART0 receive data

    uart0_rts_o    : out std_ulogic; -- hw flow control: UART0.RX ready to receive ("RTR"), low-active, optional

    uart0_cts_i    : in  std_ulogic := 'L'; -- hw flow control: UART0.TX allowed to transmit, low-active, optional

    -- secondary UART1 (available if IO_UART1_EN = true) --

    uart1_txd_o    : out std_ulogic; -- UART1 send data

    uart1_rxd_i    : in  std_ulogic := 'U'; -- UART1 receive data

    uart1_rts_o    : out std_ulogic; -- hw flow control: UART1.RX ready to receive ("RTR"), low-active, optional

    uart1_cts_i    : in  std_ulogic := 'L'; -- hw flow control: UART1.TX allowed to transmit, low-active, optional

    -- SPI (available if IO_SPI_EN = 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 := 'U'; -- controller data in, peripheral data out

    spi_csn_o      : out std_ulogic_vector(07 downto 0); -- chip-select

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

    twi_sda_io     : inout std_logic; -- twi serial data line

    twi_scl_io     : inout std_logic; -- twi serial clock line

    -- PWM (available if IO_PWM_NUM_CH > 0) --

    pwm_o          : out std_ulogic_vector(59 downto 0); -- pwm channels

    -- Custom Functions Subsystem IO (available if IO_CFS_EN = true) --

    cfs_in_i       : in  std_ulogic_vector(IO_CFS_IN_SIZE-1  downto 0) := (others => 'U'); -- custom CFS inputs conduit

    cfs_out_o      : out std_ulogic_vector(IO_CFS_OUT_SIZE-1 downto 0); -- custom CFS outputs conduit

    -- NeoPixel-compatible smart LED interface (available if IO_NEOLED_EN = true) --

    neoled_o       : out std_ulogic; -- async serial data line

    -- System time --

    mtime_i        : in  std_ulogic_vector(63 downto 0) := (others => 'U'); -- current system time from ext. MTIME (if IO_MTIME_EN = false)

    mtime_o        : out std_ulogic_vector(63 downto 0); -- current system time from int. MTIME (if IO_MTIME_EN = true)

    -- External platform interrupts (available if XIRQ_NUM_CH > 0) --

    xirq_i         : in  std_ulogic_vector(31 downto 0) := (others => 'L'); -- IRQ channels

    -- CPU interrupts --

    mtime_irq_i    : in  std_ulogic := 'L'; -- machine timer interrupt, available if IO_MTIME_EN = false

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

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

  );

end neorv32_top;

architecture neorv32_top_rtl of neorv32_top is

  -- CPU boot configuration --

  constant cpu_boot_addr_c : std_ulogic_vector(31 downto 0) := cond_sel_stdulogicvector_f(INT_BOOTLOADER_EN, boot_rom_base_c, ispace_base_c);

  -- alignment check for internal memories --

  constant imem_align_check_c : std_ulogic_vector(index_size_f(MEM_INT_IMEM_SIZE)-1 downto 0) := (others => '0');

  constant dmem_align_check_c : std_ulogic_vector(index_size_f(MEM_INT_DMEM_SIZE)-1 downto 0) := (others => '0');

  -- helpers --

  constant io_slink_en_c : boolean := boolean(SLINK_NUM_RX > 0) or boolean(SLINK_NUM_TX > 0); -- implement slink at all?

  -- reset generator --

  signal ext_rstn_sync : std_ulogic_vector(3 downto 0) := (others => '0'); -- initialize (=reset) via bitstream (for FPGAs only)

  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 clk_gen_en    : std_ulogic_vector(09 downto 0);

  signal clk_gen_en_ff : std_ulogic;

  --

  signal wdt_cg_en    : std_ulogic;

  signal uart0_cg_en  : std_ulogic;

  signal uart1_cg_en  : std_ulogic;

  signal spi_cg_en    : std_ulogic;

  signal twi_cg_en    : std_ulogic;

  signal pwm_cg_en    : std_ulogic;

  signal cfs_cg_en    : std_ulogic;

  signal neoled_cg_en : std_ulogic;

  signal gptmr_cg_en  : std_ulogic;

  signal xip_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

    ack   : std_ulogic; -- bus transfer acknowledge

    err   : std_ulogic; -- bus transfer error

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

    priv  : std_ulogic; -- current privilege level

    src   : std_ulogic; -- access source (1=instruction fetch, 0=data access)

    lock  : std_ulogic; -- exclusive access request

  end record;

  signal cpu_i, i_cache, cpu_d, p_bus : bus_interface_t;

  -- bus access error (from BUSKEEPER) --

  signal bus_error : std_ulogic;

  -- debug core interface (DCI) --

  signal dci_ndmrstn  : std_ulogic;

  signal dci_halt_req : std_ulogic;

  -- debug module interface (DMI) --

  type dmi_t is record

    rstn       : std_ulogic;

    req_valid  : std_ulogic;

    req_ready  : std_ulogic; -- DMI is allowed to make new requests when set

    req_addr   : std_ulogic_vector(06 downto 0);

    req_op     : std_ulogic; -- 0=read, 1=write

    req_data   : std_ulogic_vector(31 downto 0);

    resp_valid : std_ulogic; -- response valid when set

    resp_ready : std_ulogic; -- ready to receive respond

    resp_data  : std_ulogic_vector(31 downto 0);

    resp_err   : std_ulogic; -- 0=ok, 1=error

  end record;

  signal dmi : dmi_t;

  -- io space access --

  signal io_acc  : std_ulogic;

  signal io_rden : std_ulogic;

  signal io_wren : std_ulogic;

  -- module response bus - entry type --

  type resp_bus_entry_t is record

    rdata : std_ulogic_vector(data_width_c-1 downto 0);

    ack   : std_ulogic;

    err   : std_ulogic;

  end record;

  constant resp_bus_entry_terminate_c : resp_bus_entry_t := (rdata => (others => '0'), ack => '0', err => '0');

  -- module response bus - device ID --

  type resp_bus_id_t is (RESP_BUSKEEPER, RESP_IMEM, RESP_DMEM, RESP_BOOTROM, RESP_WISHBONE, RESP_GPIO, RESP_MTIME,

                         RESP_UART0, RESP_UART1, RESP_SPI, RESP_TWI, RESP_PWM, RESP_WDT, RESP_TRNG, RESP_CFS,

                         RESP_NEOLED, RESP_SYSINFO, RESP_OCD, RESP_SLINK, RESP_XIRQ, RESP_GPTMR, RESP_XIP_CT, RESP_XIP_IF);

  -- module response bus --

  type resp_bus_t is array (resp_bus_id_t) of resp_bus_entry_t;

  signal resp_bus : resp_bus_t := (others => resp_bus_entry_terminate_c);

  -- IRQs --

  signal fast_irq      : std_ulogic_vector(15 downto 0);

  signal mtime_irq     : std_ulogic;

  signal wdt_irq       : std_ulogic;

  signal uart0_rxd_irq : std_ulogic;

  signal uart0_txd_irq : std_ulogic;

  signal uart1_rxd_irq : std_ulogic;

  signal uart1_txd_irq : std_ulogic;

  signal spi_irq       : std_ulogic;

  signal twi_irq       : std_ulogic;

  signal cfs_irq       : std_ulogic;

  signal neoled_irq    : std_ulogic;

  signal slink_tx_irq  : std_ulogic;

  signal slink_rx_irq  : std_ulogic;

  signal xirq_irq      : std_ulogic;

  signal gptmr_irq     : std_ulogic;

  -- misc --

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

  signal ext_timeout : std_ulogic;

  signal ext_access  : std_ulogic;

  signal xip_access  : std_ulogic;

  signal xip_enable  : std_ulogic;

  signal xip_page    : std_ulogic_vector(3 downto 0);

  signal debug_mode  : std_ulogic;

begin

  -- Processor IO/Peripherals Configuration -------------------------------------------------

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

  assert false report

  "NEORV32 PROCESSOR IO Configuration: " &

  cond_sel_string_f(IO_GPIO_EN, "GPIO ", "") &

  cond_sel_string_f(IO_MTIME_EN, "MTIME ", "") &

  cond_sel_string_f(IO_UART0_EN, "UART0 ", "") &

  cond_sel_string_f(IO_UART1_EN, "UART1 ", "") &

  cond_sel_string_f(IO_SPI_EN, "SPI ", "") &

  cond_sel_string_f(IO_TWI_EN, "TWI ", "") &

  cond_sel_string_f(boolean(IO_PWM_NUM_CH > 0), "PWM ", "") &

  cond_sel_string_f(IO_WDT_EN, "WDT ", "") &

  cond_sel_string_f(IO_TRNG_EN, "TRNG ", "") &

  cond_sel_string_f(IO_CFS_EN, "CFS ", "") &

  cond_sel_string_f(io_slink_en_c, "SLINK ", "") &

  cond_sel_string_f(IO_NEOLED_EN, "NEOLED ", "") &

  cond_sel_string_f(boolean(XIRQ_NUM_CH > 0), "XIRQ ", "") &

  cond_sel_string_f(IO_GPTMR_EN, "GPTMR ", "") &

  cond_sel_string_f(IO_XIP_EN, "XIP ", "") &

  ""

  severity note;

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

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

  -- boot configuration --

  assert not (INT_BOOTLOADER_EN = true) report "NEORV32 PROCESSOR CONFIG NOTE: Boot configuration: Indirect boot via bootloader (processor-internal BOOTROM)." severity note;

  assert not ((INT_BOOTLOADER_EN = false) and (MEM_INT_IMEM_EN = true)) report "NEORV32 PROCESSOR CONFIG NOTE: Boot configuration: Direct boot from memory (processor-internal IMEM)." severity note;

  assert not ((INT_BOOTLOADER_EN = false) and (MEM_INT_IMEM_EN = false)) report "NEORV32 PROCESSOR CONFIG NOTE: Boot configuration: Direct boot from memory (processor-external (I)MEM)." severity note;

  --

  assert not ((MEM_EXT_EN = false) and (MEM_INT_DMEM_EN = false)) report "NEORV32 PROCESSOR CONFIG ERROR! Core cannot fetch data without external memory interface and internal IMEM." severity error;

  assert not ((MEM_EXT_EN = false) and (MEM_INT_IMEM_EN = false) and (INT_BOOTLOADER_EN = false)) report "NEORV32 PROCESSOR CONFIG ERROR! Core cannot fetch instructions without external memory interface, internal IMEM and bootloader." severity error;

  -- memory system - size --

  assert not ((MEM_INT_DMEM_EN = true) and (is_power_of_two_f(MEM_INT_IMEM_SIZE) = false)) report "NEORV32 PROCESSOR CONFIG WARNING! MEM_INT_IMEM_SIZE should be a power of 2 to allow optimal hardware mapping." severity warning;

  assert not ((MEM_INT_IMEM_EN = true) and (is_power_of_two_f(MEM_INT_DMEM_SIZE) = false)) report "NEORV32 PROCESSOR CONFIG WARNING! MEM_INT_DMEM_SIZE should be a power of 2 to allow optimal hardware mapping." severity warning;

  -- memory system - alignment --

  assert not (ispace_base_c(1 downto 0) /= "00") report "NEORV32 PROCESSOR CONFIG ERROR! Instruction memory space base address must be 4-byte-aligned." severity error;

  assert not (dspace_base_c(1 downto 0) /= "00") report "NEORV32 PROCESSOR CONFIG ERROR! Data memory space base address must be 4-byte-aligned." severity error;

  assert not ((ispace_base_c(index_size_f(MEM_INT_IMEM_SIZE)-1 downto 0) /= imem_align_check_c) and (MEM_INT_IMEM_EN = true)) report "NEORV32 PROCESSOR CONFIG ERROR! Instruction memory space base address has to be aligned to IMEM size." severity error;

  assert not ((dspace_base_c(index_size_f(MEM_INT_DMEM_SIZE)-1 downto 0) /= dmem_align_check_c) and (MEM_INT_DMEM_EN = true)) report "NEORV32 PROCESSOR CONFIG ERROR! Data memory space base address has to be aligned to DMEM size." severity error;

  -- memory system - layout warning --

  assert not (ispace_base_c /= x"00000000") report "NEORV32 PROCESSOR CONFIG WARNING! Non-default base address for instruction address space. Make sure this is sync with the software framework." severity warning;

  assert not (dspace_base_c /= x"80000000") report "NEORV32 PROCESSOR CONFIG WARNING! Non-default base address for data address space. Make sure this is sync with the software framework." severity warning;

  -- memory system - the i-cache is intended to accelerate instruction fetch via the external memory interface only --

  assert not ((ICACHE_EN = true) and (MEM_EXT_EN = false)) report "NEORV32 PROCESSOR CONFIG NOTE. Implementing i-cache without having the external memory interface implemented. The i-cache is intended to accelerate instruction fetch via the external memory interface." severity note;

  -- on-chip debugger --

  assert not (ON_CHIP_DEBUGGER_EN = true) report "NEORV32 PROCESSOR CONFIG NOTE: Implementing on-chip debugger (OCD)." severity note;

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

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

  reset_generator: process(rstn_i, clk_i)

  begin

    if (rstn_i = '0') then

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

      ext_rstn      <= '0';

      sys_rstn      <= '0';

    elsif rising_edge(clk_i) then

      -- keep internal reset active for at least <ext_rstn_sync'size> clock cycles --

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

      -- beautified external reset signal --

      if (and_reduce_f(ext_rstn_sync) = '1') then

        ext_rstn <= '1';

      else

        ext_rstn <= '0';

      end if;

      -- system reset: can also be triggered by watchdog and debug module --

      sys_rstn <= ext_rstn and wdt_rstn and dci_ndmrstn;

    end if;

  end process reset_generator;

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

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

  clock_generator: process(sys_rstn, clk_i)

  begin

    if (sys_rstn = '0') then

      clk_gen_en_ff <= '0';

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

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

    elsif rising_edge(clk_i) then

      clk_gen_en_ff <= or_reduce_f(clk_gen_en);

      if (clk_gen_en_ff = '1') then

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

      else

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

      end if;

      clk_div_ff <= clk_div;

    end if;

  end process clock_generator;

  -- clock enables: 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

  -- fresh clocks anyone? --

  clk_gen_en(0) <= wdt_cg_en;

  clk_gen_en(1) <= uart0_cg_en;

  clk_gen_en(2) <= uart1_cg_en;

  clk_gen_en(3) <= spi_cg_en;

  clk_gen_en(4) <= twi_cg_en;

  clk_gen_en(5) <= pwm_cg_en;

  clk_gen_en(6) <= cfs_cg_en;

  clk_gen_en(7) <= neoled_cg_en;

  clk_gen_en(8) <= gptmr_cg_en;

  clk_gen_en(9) <= xip_cg_en;

  -- CPU Core -------------------------------------------------------------------------------

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

  neorv32_cpu_inst: neorv32_cpu

  generic map (

    -- General --

    HW_THREAD_ID                 => HW_THREAD_ID,                 -- hardware thread id

    CPU_BOOT_ADDR                => cpu_boot_addr_c,              -- cpu boot address

    CPU_DEBUG_ADDR               => dm_base_c,                    -- cpu debug mode start address

    -- RISC-V CPU Extensions --

    CPU_EXTENSION_RISCV_A        => CPU_EXTENSION_RISCV_A,        -- implement atomic extension?

    CPU_EXTENSION_RISCV_B        => CPU_EXTENSION_RISCV_B,        -- implement bit-manipulation 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 mul/div extension?

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

    CPU_EXTENSION_RISCV_Zfinx    => CPU_EXTENSION_RISCV_Zfinx,    -- implement 32-bit floating-point extension (using INT reg!)

    CPU_EXTENSION_RISCV_Zicsr    => CPU_EXTENSION_RISCV_Zicsr,    -- implement CSR system?

    CPU_EXTENSION_RISCV_Zicntr   => CPU_EXTENSION_RISCV_Zicntr,   -- implement base counters?

    CPU_EXTENSION_RISCV_Zihpm    => CPU_EXTENSION_RISCV_Zihpm,    -- implement hardware performance monitors?

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

    CPU_EXTENSION_RISCV_Zmmul    => CPU_EXTENSION_RISCV_Zmmul,    -- implement multiply-only M sub-extension?

    CPU_EXTENSION_RISCV_Zxcfu    => CPU_EXTENSION_RISCV_Zxcfu,    -- implement custom (instr.) functions unit?

    CPU_EXTENSION_RISCV_DEBUG    => ON_CHIP_DEBUGGER_EN,          -- implement CPU debug mode?

    -- Extension Options --

    FAST_MUL_EN                  => FAST_MUL_EN,                  -- use DSPs for M extension's multiplier

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

    CPU_CNT_WIDTH                => CPU_CNT_WIDTH,                -- total width of CPU cycle and instret counters (0..64)

    CPU_IPB_ENTRIES              => CPU_IPB_ENTRIES,              -- entries is instruction prefetch buffer, has to be a power of 2

    -- Physical Memory Protection (PMP) --

    PMP_NUM_REGIONS              => PMP_NUM_REGIONS,              -- number of regions (0..16)

    PMP_MIN_GRANULARITY          => PMP_MIN_GRANULARITY,          -- minimal region granularity in bytes, has to be a power of 2, min 4 bytes

    -- Hardware Performance Monitors (HPM) --

    HPM_NUM_CNTS                 => HPM_NUM_CNTS,                 -- number of implemented HPM counters (0..29)

    HPM_CNT_WIDTH                => HPM_CNT_WIDTH                 -- total size of HPM counters (0..64)

  )

  port map (

    -- global control --

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

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

    sleep_o       => open,        -- cpu is in sleep mode when set

    debug_o       => debug_mode,  -- cpu is in debug mode when set

    -- 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_lock_o  => cpu_i.lock,  -- exclusive access request

    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

    i_bus_priv_o  => cpu_i.priv,  -- privilege level

    -- 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_lock_o  => cpu_d.lock,  -- exclusive access request

    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

    d_bus_priv_o  => cpu_d.priv,  -- privilege level

    -- system time input from MTIME --

    time_i        => mtime_time,  -- current system time

    -- non-maskable interrupt --

    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,    -- fast interrupt trigger

    -- debug mode (halt) request --

    db_halt_req_i => dci_halt_req

  );

  -- misc --

  cpu_i.src <= '1'; -- initialized but unused

  cpu_d.src <= '0'; -- initialized but unused

  -- advanced memory control --

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

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

  -- fast interrupt requests (FIRQs) - triggers are SINGLE-SHOT --

  fast_irq(00) <= wdt_irq;       -- HIGHEST PRIORITY - watchdog

  fast_irq(01) <= cfs_irq;       -- custom functions subsystem

  fast_irq(02) <= uart0_rxd_irq; -- primary UART (UART0) RX

  fast_irq(03) <= uart0_txd_irq; -- primary UART (UART0) TX

  fast_irq(04) <= uart1_rxd_irq; -- secondary UART (UART1) RX

  fast_irq(05) <= uart1_txd_irq; -- secondary UART (UART1) TX

  fast_irq(06) <= spi_irq;       -- SPI transfer done

  fast_irq(07) <= twi_irq;       -- TWI transfer done

  fast_irq(08) <= xirq_irq;      -- external interrupt controller

  fast_irq(09) <= neoled_irq;    -- NEOLED buffer IRQ

  fast_irq(10) <= slink_rx_irq;  -- SLINK RX