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

-- # << NEORV32 - Main VHDL package file >>                                                        #

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

-- # BSD 3-Clause License                                                                          #

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

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

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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;

package neorv32_package is

  -- Architecture Configuration -------------------------------------------------------------

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

  constant ispace_base_c  : std_ulogic_vector(31 downto 0) := x"00000000"; -- default instruction memory address space base address

  constant dspace_base_c  : std_ulogic_vector(31 downto 0) := x"80000000"; -- default data memory address space base address

  constant bus_timeout_c  : natural := 127; -- cycles after which an *unacknowledged* bus access will timeout and trigger an access exception

  constant wb_pipe_mode_c : boolean := false; -- false: classic/standard wishbone mode, true: pipelined wishbone mode

  constant ipb_entries_c  : natural := 2; -- entries in instruction prefetch buffer, must be a power of 2, default=2

  constant rf_r0_is_reg_c : boolean := true; -- reg_file.r0 is a physical register that has to be initialized to zero by the CPU HW

  -- Architecture Constants -----------------------------------------------------------------

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

  constant data_width_c : natural := 32; -- data width - do not change!

  constant hw_version_c : std_ulogic_vector(31 downto 0) := x"01040801"; -- no touchy!

  constant pmp_max_r_c  : natural := 8; -- max PMP regions - FIXED!

  constant archid_c     : natural := 19; -- official NEORV32 architecture ID - hands off!

  -- Helper Functions -----------------------------------------------------------------------

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

  function index_size_f(input : natural) return natural;

  function cond_sel_natural_f(cond : boolean; val_t : natural; val_f : natural) return natural;

  function cond_sel_stdulogicvector_f(cond : boolean; val_t : std_ulogic_vector; val_f : std_ulogic_vector) return std_ulogic_vector;

  function bool_to_ulogic_f(cond : boolean) return std_ulogic;

  function or_all_f(a : std_ulogic_vector) return std_ulogic;

  function and_all_f(a : std_ulogic_vector) return std_ulogic;

  function xor_all_f(a : std_ulogic_vector) return std_ulogic;

  function xnor_all_f(a : std_ulogic_vector) return std_ulogic;

  function to_hexchar_f(input : std_ulogic_vector(3 downto 0)) return character;

  function bit_rev_f(input : std_ulogic_vector) return std_ulogic_vector;

  function is_power_of_two_f(input : natural) return boolean;

  -- Internal Types -------------------------------------------------------------------------

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

  type pmp_ctrl_if_t is array (0 to pmp_max_r_c-1) of std_ulogic_vector(7 downto 0);

  type pmp_addr_if_t is array (0 to pmp_max_r_c-1) of std_ulogic_vector(33 downto 0);

  -- Processor-Internal Address Space Layout ------------------------------------------------

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

  -- Internal Instruction Memory (IMEM) and Date Memory (DMEM) --

  constant imem_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := ispace_base_c; -- internal instruction memory base address

  constant dmem_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := dspace_base_c; -- internal data memory base address

  --> memory sizes are configured via top's generics

  -- Internal Bootloader ROM --

  constant boot_rom_base_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFF0000"; -- bootloader base address, fixed!

  constant boot_rom_size_c      : natural := 4*1024; -- bytes

  constant boot_rom_max_size_c  : natural := 32*1024; -- bytes, fixed!

  -- IO: Peripheral Devices ("IO") Area --

  -- Control register(s) (including the device-enable) should be located at the base address of each device

  constant io_base_c            : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF80";

  constant io_size_c            : natural := 32*4; -- bytes, fixed!

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

  constant gpio_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF80"; -- base address, fixed!

  constant gpio_size_c          : natural := 2*4; -- bytes

  constant gpio_in_addr_c       : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF80";

  constant gpio_out_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF84";

  -- True Random Number Generator (TRNG) --

  constant trng_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF88"; -- base address, fixed!

  constant trng_size_c          : natural := 1*4; -- bytes

  constant trng_ctrl_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF88";

  -- Watch Dog Timer (WDT) --

  constant wdt_base_c           : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF8C"; -- base address, fixed!

  constant wdt_size_c           : natural := 1*4; -- bytes

  constant wdt_ctrl_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF8C";

  -- Machine System Timer (MTIME) --

  constant mtime_base_c         : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF90"; -- base address, fixed!

  constant mtime_size_c         : natural := 4*4; -- bytes

  constant mtime_time_lo_addr_c : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF90";

  constant mtime_time_hi_addr_c : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF94";

  constant mtime_cmp_lo_addr_c  : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF98";

  constant mtime_cmp_hi_addr_c  : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFF9C";

  -- Universal Asynchronous Receiver/Transmitter (UART) --

  constant uart_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFA0"; -- base address, fixed!

  constant uart_size_c          : natural := 2*4; -- bytes

  constant uart_ctrl_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFA0";

  constant uart_rtx_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFA4";

  -- Serial Peripheral Interface (SPI) --

  constant spi_base_c           : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFA8"; -- base address, fixed!

  constant spi_size_c           : natural := 2*4; -- bytes

  constant spi_ctrl_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFA8";

  constant spi_rtx_addr_c       : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFAC";

  -- Two Wire Interface (TWI) --

  constant twi_base_c           : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFB0"; -- base address, fixed!

  constant twi_size_c           : natural := 2*4; -- bytes

  constant twi_ctrl_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFB0";

  constant twi_rtx_addr_c       : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFB4";

  -- Pulse-Width Modulation Controller (PWM) --

  constant pwm_base_c           : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFB8"; -- base address, fixed!

  constant pwm_size_c           : natural := 2*4; -- bytes

  constant pwm_ctrl_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFB8";

  constant pwm_duty_addr_c      : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFBC";

  -- Custom Functions Unit 0 (CFU0) --

  constant cfu0_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFC0"; -- base address, fixed!

  constant cfu0_size_c          : natural := 4*4; -- bytes

  constant cfu0_reg0_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFC0";

  constant cfu0_reg1_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFC4";

  constant cfu0_reg2_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFC8";

  constant cfu0_reg3_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFCC";

  -- Custom Functions Unit 1 (CFU1) --

  constant cfu1_base_c          : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFD0"; -- base address, fixed!

  constant cfu1_size_c          : natural := 4*4; -- bytes

  constant cfu1_reg0_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFD0";

  constant cfu1_reg1_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFD4";

  constant cfu1_reg2_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFD8";

  constant cfu1_reg3_addr_c     : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFDC";

  -- System Information Memory (SYSINFO) --

  constant sysinfo_base_c       : std_ulogic_vector(data_width_c-1 downto 0) := x"FFFFFFE0"; -- base address, fixed!

  constant sysinfo_size_c       : natural := 8*4; -- bytes

  -- Main Control Bus -----------------------------------------------------------------------

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

  -- register file --

  constant ctrl_rf_in_mux_lsb_c : natural :=  0; -- input source select lsb (10=MEM, 11=CSR)

  constant ctrl_rf_in_mux_msb_c : natural :=  1; -- input source select msb (0-=ALU)

  constant ctrl_rf_rs1_adr0_c   : natural :=  2; -- source register 1 address bit 0

  constant ctrl_rf_rs1_adr1_c   : natural :=  3; -- source register 1 address bit 1

  constant ctrl_rf_rs1_adr2_c   : natural :=  4; -- source register 1 address bit 2

  constant ctrl_rf_rs1_adr3_c   : natural :=  5; -- source register 1 address bit 3

  constant ctrl_rf_rs1_adr4_c   : natural :=  6; -- source register 1 address bit 4

  constant ctrl_rf_rs2_adr0_c   : natural :=  7; -- source register 2 address bit 0

  constant ctrl_rf_rs2_adr1_c   : natural :=  8; -- source register 2 address bit 1

  constant ctrl_rf_rs2_adr2_c   : natural :=  9; -- source register 2 address bit 2

  constant ctrl_rf_rs2_adr3_c   : natural := 10; -- source register 2 address bit 3

  constant ctrl_rf_rs2_adr4_c   : natural := 11; -- source register 2 address bit 4

  constant ctrl_rf_rd_adr0_c    : natural := 12; -- destiantion register address bit 0

  constant ctrl_rf_rd_adr1_c    : natural := 13; -- destiantion register address bit 1

  constant ctrl_rf_rd_adr2_c    : natural := 14; -- destiantion register address bit 2

  constant ctrl_rf_rd_adr3_c    : natural := 15; -- destiantion register address bit 3

  constant ctrl_rf_rd_adr4_c    : natural := 16; -- destiantion register address bit 4

  constant ctrl_rf_wb_en_c      : natural := 17; -- write back enable

  constant ctrl_rf_r0_we_c      : natural := 18; -- force write access and force rd=r0

  -- alu --

  constant ctrl_alu_arith_c     : natural := 19; -- ALU arithmetic command

  constant ctrl_alu_logic0_c    : natural := 20; -- ALU logic command bit 0

  constant ctrl_alu_logic1_c    : natural := 21; -- ALU logic command bit 1

  constant ctrl_alu_func0_c     : natural := 22; -- ALU function select command bit 0

  constant ctrl_alu_func1_c     : natural := 23; -- ALU function select command bit 1

  constant ctrl_alu_addsub_c    : natural := 24; -- 0=ADD, 1=SUB

  constant ctrl_alu_opa_mux_c   : natural := 25; -- operand A select (0=rs1, 1=PC)

  constant ctrl_alu_opb_mux_c   : natural := 26; -- operand B select (0=rs2, 1=IMM)

  constant ctrl_alu_unsigned_c  : natural := 27; -- is unsigned ALU operation

  constant ctrl_alu_shift_dir_c : natural := 28; -- shift direction (0=left, 1=right)

  constant ctrl_alu_shift_ar_c  : natural := 29; -- is arithmetic shift

  -- bus interface --

  constant ctrl_bus_size_lsb_c  : natural := 30; -- transfer size lsb (00=byte, 01=half-word)

  constant ctrl_bus_size_msb_c  : natural := 31; -- transfer size msb (10=word, 11=?)

  constant ctrl_bus_rd_c        : natural := 32; -- read data request

  constant ctrl_bus_wr_c        : natural := 33; -- write data request

  constant ctrl_bus_if_c        : natural := 34; -- instruction fetch request

  constant ctrl_bus_mo_we_c     : natural := 35; -- memory address and data output register write enable

  constant ctrl_bus_mi_we_c     : natural := 36; -- memory data input register write enable

  constant ctrl_bus_unsigned_c  : natural := 37; -- is unsigned load

  constant ctrl_bus_ierr_ack_c  : natural := 38; -- acknowledge instruction fetch bus exceptions

  constant ctrl_bus_derr_ack_c  : natural := 39; -- acknowledge data access bus exceptions

  constant ctrl_bus_fence_c     : natural := 40; -- executed fence operation

  constant ctrl_bus_fencei_c    : natural := 41; -- executed fencei operation

  constant ctrl_bus_lock_c      : natural := 42; -- locked/exclusive bus access

  -- co-processors --

  constant ctrl_cp_id_lsb_c     : natural := 43; -- cp select ID lsb

  constant ctrl_cp_id_msb_c     : natural := 44; -- cp select ID msb

  -- current privilege level --

  constant ctrl_priv_lvl_lsb_c  : natural := 45; -- privilege level lsb

  constant ctrl_priv_lvl_msb_c  : natural := 46; -- privilege level msb

  -- instruction's control blocks --

  constant ctrl_ir_funct3_0_c   : natural := 47; -- funct3 bit 0

  constant ctrl_ir_funct3_1_c   : natural := 48; -- funct3 bit 1

  constant ctrl_ir_funct3_2_c   : natural := 49; -- funct3 bit 2

  constant ctrl_ir_funct12_0_c  : natural := 50; -- funct12 bit 0

  constant ctrl_ir_funct12_1_c  : natural := 51; -- funct12 bit 1

  constant ctrl_ir_funct12_2_c  : natural := 52; -- funct12 bit 2

  constant ctrl_ir_funct12_3_c  : natural := 53; -- funct12 bit 3

  constant ctrl_ir_funct12_4_c  : natural := 54; -- funct12 bit 4

  constant ctrl_ir_funct12_5_c  : natural := 55; -- funct12 bit 5

  constant ctrl_ir_funct12_6_c  : natural := 56; -- funct12 bit 6

  constant ctrl_ir_funct12_7_c  : natural := 57; -- funct12 bit 7

  constant ctrl_ir_funct12_8_c  : natural := 58; -- funct12 bit 8

  constant ctrl_ir_funct12_9_c  : natural := 59; -- funct12 bit 9

  constant ctrl_ir_funct12_10_c : natural := 60; -- funct12 bit 10

  constant ctrl_ir_funct12_11_c : natural := 61; -- funct12 bit 11

  -- control bus size --

  constant ctrl_width_c         : natural := 62; -- control bus size

  -- ALU Comparator Bus ---------------------------------------------------------------------

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

  constant alu_cmp_equal_c : natural := 0;

  constant alu_cmp_less_c  : natural := 1; -- for signed and unsigned comparisons

  -- RISC-V Opcode Layout -------------------------------------------------------------------

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

  constant instr_opcode_lsb_c  : natural :=  0; -- opcode bit 0

  constant instr_opcode_msb_c  : natural :=  6; -- opcode bit 6

  constant instr_rd_lsb_c      : natural :=  7; -- destination register address bit 0

  constant instr_rd_msb_c      : natural := 11; -- destination register address bit 4

  constant instr_funct3_lsb_c  : natural := 12; -- funct3 bit 0

  constant instr_funct3_msb_c  : natural := 14; -- funct3 bit 2

  constant instr_rs1_lsb_c     : natural := 15; -- source register 1 address bit 0

  constant instr_rs1_msb_c     : natural := 19; -- source register 1 address bit 4

  constant instr_rs2_lsb_c     : natural := 20; -- source register 2 address bit 0

  constant instr_rs2_msb_c     : natural := 24; -- source register 2 address bit 4

  constant instr_funct7_lsb_c  : natural := 25; -- funct7 bit 0

  constant instr_funct7_msb_c  : natural := 31; -- funct7 bit 6

  constant instr_funct12_lsb_c : natural := 20; -- funct12 bit 0

  constant instr_funct12_msb_c : natural := 31; -- funct12 bit 11

  constant instr_imm12_lsb_c   : natural := 20; -- immediate12 bit 0

  constant instr_imm12_msb_c   : natural := 31; -- immediate12 bit 11

  constant instr_imm20_lsb_c   : natural := 12; -- immediate20 bit 0

  constant instr_imm20_msb_c   : natural := 31; -- immediate20 bit 21

  constant instr_csr_id_lsb_c  : natural := 20; -- csr select bit 0

  constant instr_csr_id_msb_c  : natural := 31; -- csr select bit 11

  constant instr_funct5_lsb_c  : natural := 27; -- funct5 select bit 0

  constant instr_funct5_msb_c  : natural := 31; -- funct5 select bit 4

  -- RISC-V Opcodes -------------------------------------------------------------------------

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

  -- alu --

  constant opcode_lui_c    : std_ulogic_vector(6 downto 0) := "0110111"; -- load upper immediate

  constant opcode_auipc_c  : std_ulogic_vector(6 downto 0) := "0010111"; -- add upper immediate to PC

  constant opcode_alui_c   : std_ulogic_vector(6 downto 0) := "0010011"; -- ALU operation with immediate (operation via funct3 and funct7)

  constant opcode_alu_c    : std_ulogic_vector(6 downto 0) := "0110011"; -- ALU operation (operation via funct3 and funct7)

  -- control flow --

  constant opcode_jal_c    : std_ulogic_vector(6 downto 0) := "1101111"; -- jump and link

  constant opcode_jalr_c   : std_ulogic_vector(6 downto 0) := "1100111"; -- jump and link with register

  constant opcode_branch_c : std_ulogic_vector(6 downto 0) := "1100011"; -- branch (condition set via funct3)

  -- memory access --

  constant opcode_load_c   : std_ulogic_vector(6 downto 0) := "0000011"; -- load (data type via funct3)

  constant opcode_store_c  : std_ulogic_vector(6 downto 0) := "0100011"; -- store (data type via funct3)

  -- system/csr --

  constant opcode_fence_c  : std_ulogic_vector(6 downto 0) := "0001111"; -- fence / fence.i

  constant opcode_syscsr_c : std_ulogic_vector(6 downto 0) := "1110011"; -- system/csr access (type via funct3)

  -- atomic operations (A) --

  constant opcode_atomic_c : std_ulogic_vector(6 downto 0) := "0101111"; -- atomic operations (A extension)

  -- RISC-V Funct3 --------------------------------------------------------------------------

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

  -- control flow --

  constant funct3_beq_c    : std_ulogic_vector(2 downto 0) := "000"; -- branch if equal

  constant funct3_bne_c    : std_ulogic_vector(2 downto 0) := "001"; -- branch if not equal

  constant funct3_blt_c    : std_ulogic_vector(2 downto 0) := "100"; -- branch if less than

  constant funct3_bge_c    : std_ulogic_vector(2 downto 0) := "101"; -- branch if greater than or equal

  constant funct3_bltu_c   : std_ulogic_vector(2 downto 0) := "110"; -- branch if less than (unsigned)

  constant funct3_bgeu_c   : std_ulogic_vector(2 downto 0) := "111"; -- branch if greater than or equal (unsigned)

  -- memory access --

  constant funct3_lb_c     : std_ulogic_vector(2 downto 0) := "000"; -- load byte

  constant funct3_lh_c     : std_ulogic_vector(2 downto 0) := "001"; -- load half word

  constant funct3_lw_c     : std_ulogic_vector(2 downto 0) := "010"; -- load word

  constant funct3_lbu_c    : std_ulogic_vector(2 downto 0) := "100"; -- load byte (unsigned)

  constant funct3_lhu_c    : std_ulogic_vector(2 downto 0) := "101"; -- load half word (unsigned)

  constant funct3_sb_c     : std_ulogic_vector(2 downto 0) := "000"; -- store byte

  constant funct3_sh_c     : std_ulogic_vector(2 downto 0) := "001"; -- store half word

  constant funct3_sw_c     : std_ulogic_vector(2 downto 0) := "010"; -- store word

  -- alu --

  constant funct3_subadd_c : std_ulogic_vector(2 downto 0) := "000"; -- sub/add via funct7

  constant funct3_sll_c    : std_ulogic_vector(2 downto 0) := "001"; -- shift logical left

  constant funct3_slt_c    : std_ulogic_vector(2 downto 0) := "010"; -- set on less

  constant funct3_sltu_c   : std_ulogic_vector(2 downto 0) := "011"; -- set on less unsigned

  constant funct3_xor_c    : std_ulogic_vector(2 downto 0) := "100"; -- xor

  constant funct3_sr_c     : std_ulogic_vector(2 downto 0) := "101"; -- shift right via funct7

  constant funct3_or_c     : std_ulogic_vector(2 downto 0) := "110"; -- or

  constant funct3_and_c    : std_ulogic_vector(2 downto 0) := "111"; -- and

  -- system/csr --

  constant funct3_env_c    : std_ulogic_vector(2 downto 0) := "000"; -- ecall, ebreak, mret, wfi

  constant funct3_csrrw_c  : std_ulogic_vector(2 downto 0) := "001"; -- atomic r/w

  constant funct3_csrrs_c  : std_ulogic_vector(2 downto 0) := "010"; -- atomic read & set bit

  constant funct3_csrrc_c  : std_ulogic_vector(2 downto 0) := "011"; -- atomic read & clear bit

  --

  constant funct3_csrrwi_c : std_ulogic_vector(2 downto 0) := "101"; -- atomic r/w immediate

  constant funct3_csrrsi_c : std_ulogic_vector(2 downto 0) := "110"; -- atomic read & set bit immediate

  constant funct3_csrrci_c : std_ulogic_vector(2 downto 0) := "111"; -- atomic read & clear bit immediate

  -- fence --

  constant funct3_fence_c  : std_ulogic_vector(2 downto 0) := "000"; -- fence - order IO/memory access (->NOP)

  constant funct3_fencei_c : std_ulogic_vector(2 downto 0) := "001"; -- fencei - instructon stream sync

  -- RISC-V Funct12 -------------------------------------------------------------------------

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

  -- system --

  constant funct12_ecall_c  : std_ulogic_vector(11 downto 0) := x"000"; -- ECALL

  constant funct12_ebreak_c : std_ulogic_vector(11 downto 0) := x"001"; -- EBREAK

  constant funct12_mret_c   : std_ulogic_vector(11 downto 0) := x"302"; -- MRET

  constant funct12_wfi_c    : std_ulogic_vector(11 downto 0) := x"105"; -- WFI

  -- RISC-V Funct5 --------------------------------------------------------------------------

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

  -- atomic operations --

  constant funct5_a_lr_c : std_ulogic_vector(4 downto 0) := "00010"; -- LR

  constant funct5_a_sc_c : std_ulogic_vector(4 downto 0) := "00011"; -- SC

  -- RISC-V CSR Addresses -------------------------------------------------------------------

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

  constant csr_mstatus_c   : std_ulogic_vector(11 downto 0) := x"300"; -- mstatus

  constant csr_misa_c      : std_ulogic_vector(11 downto 0) := x"301"; -- misa

  constant csr_mie_c       : std_ulogic_vector(11 downto 0) := x"304"; -- mie

  constant csr_mtvec_c     : std_ulogic_vector(11 downto 0) := x"305"; -- mtvec

  --

  constant csr_mscratch_c  : std_ulogic_vector(11 downto 0) := x"340"; -- mscratch

  constant csr_mepc_c      : std_ulogic_vector(11 downto 0) := x"341"; -- mepc

  constant csr_mcause_c    : std_ulogic_vector(11 downto 0) := x"342"; -- mcause

  constant csr_mtval_c     : std_ulogic_vector(11 downto 0) := x"343"; -- mtval

  constant csr_mip_c       : std_ulogic_vector(11 downto 0) := x"344"; -- mip

  --

  constant csr_pmpcfg0_c   : std_ulogic_vector(11 downto 0) := x"3a0"; -- pmpcfg0

  constant csr_pmpcfg1_c   : std_ulogic_vector(11 downto 0) := x"3a1"; -- pmpcfg1

  --

  constant csr_pmpaddr0_c  : std_ulogic_vector(11 downto 0) := x"3b0"; -- pmpaddr0

  constant csr_pmpaddr1_c  : std_ulogic_vector(11 downto 0) := x"3b1"; -- pmpaddr1

  constant csr_pmpaddr2_c  : std_ulogic_vector(11 downto 0) := x"3b2"; -- pmpaddr2

  constant csr_pmpaddr3_c  : std_ulogic_vector(11 downto 0) := x"3b3"; -- pmpaddr3

  constant csr_pmpaddr4_c  : std_ulogic_vector(11 downto 0) := x"3b4"; -- pmpaddr4

  constant csr_pmpaddr5_c  : std_ulogic_vector(11 downto 0) := x"3b5"; -- pmpaddr5

  constant csr_pmpaddr6_c  : std_ulogic_vector(11 downto 0) := x"3b6"; -- pmpaddr6

  constant csr_pmpaddr7_c  : std_ulogic_vector(11 downto 0) := x"3b7"; -- pmpaddr7

  --

  constant csr_mcycle_c    : std_ulogic_vector(11 downto 0) := x"b00"; -- mcycle

  constant csr_minstret_c  : std_ulogic_vector(11 downto 0) := x"b02"; -- minstret

  --

  constant csr_mcycleh_c   : std_ulogic_vector(11 downto 0) := x"b80"; -- mcycleh

  constant csr_minstreth_c : std_ulogic_vector(11 downto 0) := x"b82"; -- minstreth

  --

  constant csr_cycle_c     : std_ulogic_vector(11 downto 0) := x"c00"; -- cycle

  constant csr_time_c      : std_ulogic_vector(11 downto 0) := x"c01"; -- time

  constant csr_instret_c   : std_ulogic_vector(11 downto 0) := x"c02"; -- instret

  --

  constant csr_cycleh_c    : std_ulogic_vector(11 downto 0) := x"c80"; -- cycleh

  constant csr_timeh_c     : std_ulogic_vector(11 downto 0) := x"c81"; -- timeh

  constant csr_instreth_c  : std_ulogic_vector(11 downto 0) := x"c82"; -- instreth

  --

  constant csr_mvendorid_c : std_ulogic_vector(11 downto 0) := x"f11"; -- mvendorid

  constant csr_marchid_c   : std_ulogic_vector(11 downto 0) := x"f12"; -- marchid

  constant csr_mimpid_c    : std_ulogic_vector(11 downto 0) := x"f13"; -- mimpid

  constant csr_mhartid_c   : std_ulogic_vector(11 downto 0) := x"f14"; -- mhartid

  --

  constant csr_mzext_c     : std_ulogic_vector(11 downto 0) := x"fc0"; -- mzext (neorv32-custom)

  -- Co-Processor Operations ----------------------------------------------------------------

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

  -- cp ids --

  constant cp_sel_muldiv_c : std_ulogic_vector(1 downto 0) := "00"; -- MULDIV

  constant cp_sel_atomic_c : std_ulogic_vector(1 downto 0) := "01"; -- atomic operations success/failure evaluation

--constant cp_sel_reserv_c : std_ulogic_vector(1 downto 0) := "10"; -- reserved

--constant cp_sel_reserv_c : std_ulogic_vector(1 downto 0) := "11"; -- reserved

  -- muldiv cp --

  constant cp_op_mul_c    : std_ulogic_vector(2 downto 0) := "000"; -- mul

  constant cp_op_mulh_c   : std_ulogic_vector(2 downto 0) := "001"; -- mulh

  constant cp_op_mulhsu_c : std_ulogic_vector(2 downto 0) := "010"; -- mulhsu

  constant cp_op_mulhu_c  : std_ulogic_vector(2 downto 0) := "011"; -- mulhu

  constant cp_op_div_c    : std_ulogic_vector(2 downto 0) := "100"; -- div

  constant cp_op_divu_c   : std_ulogic_vector(2 downto 0) := "101"; -- divu

  constant cp_op_rem_c    : std_ulogic_vector(2 downto 0) := "110"; -- rem

  constant cp_op_remu_c   : std_ulogic_vector(2 downto 0) := "111"; -- remu

  -- ALU Function Codes ---------------------------------------------------------------------

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

  -- arithmetic core --

  constant alu_arith_cmd_addsub_c : std_ulogic := '0'; -- r.arith <= A +/- B

  constant alu_arith_cmd_slt_c    : std_ulogic := '1'; -- r.arith <= A < B

  -- logic core --

  constant alu_logic_cmd_movb_c   : std_ulogic_vector(1 downto 0) := "00"; -- r.logic <= B

  constant alu_logic_cmd_xor_c    : std_ulogic_vector(1 downto 0) := "01"; -- r.logic <= A xor B

  constant alu_logic_cmd_or_c     : std_ulogic_vector(1 downto 0) := "10"; -- r.logic <= A or B

  constant alu_logic_cmd_and_c    : std_ulogic_vector(1 downto 0) := "11"; -- r.logic <= A and B

  -- function select (actual alu result) --

  constant alu_func_cmd_arith_c   : std_ulogic_vector(1 downto 0) := "00"; -- r <= r.arith

  constant alu_func_cmd_logic_c   : std_ulogic_vector(1 downto 0) := "01"; -- r <= r.logic

  constant alu_func_cmd_shift_c   : std_ulogic_vector(1 downto 0) := "10"; -- r <= A <</>> B (iterative)

  constant alu_func_cmd_copro_c   : std_ulogic_vector(1 downto 0) := "11"; -- r <= CP result (iterative)

  -- Trap ID Codes --------------------------------------------------------------------------

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

  -- RISC-V compliant exceptions --

  constant trap_ima_c   : std_ulogic_vector(5 downto 0) := "0" & "00000"; -- 0.0:  instruction misaligned

  constant trap_iba_c   : std_ulogic_vector(5 downto 0) := "0" & "00001"; -- 0.1:  instruction access fault

  constant trap_iil_c   : std_ulogic_vector(5 downto 0) := "0" & "00010"; -- 0.2:  illegal instruction

  constant trap_brk_c   : std_ulogic_vector(5 downto 0) := "0" & "00011"; -- 0.3:  breakpoint

  constant trap_lma_c   : std_ulogic_vector(5 downto 0) := "0" & "00100"; -- 0.4:  load address misaligned

  constant trap_lbe_c   : std_ulogic_vector(5 downto 0) := "0" & "00101"; -- 0.5:  load access fault

  constant trap_sma_c   : std_ulogic_vector(5 downto 0) := "0" & "00110"; -- 0.6:  store address misaligned

  constant trap_sbe_c   : std_ulogic_vector(5 downto 0) := "0" & "00111"; -- 0.7:  store access fault

  constant trap_menv_c  : std_ulogic_vector(5 downto 0) := "0" & "01011"; -- 0.11: environment call from m-mode

  -- RISC-V compliant interrupts --

  constant trap_msi_c   : std_ulogic_vector(5 downto 0) := "1" & "00011"; -- 1.3:  machine software interrupt

  constant trap_mti_c   : std_ulogic_vector(5 downto 0) := "1" & "00111"; -- 1.7:  machine timer interrupt

  constant trap_mei_c   : std_ulogic_vector(5 downto 0) := "1" & "01011"; -- 1.11: machine external interrupt

  -- NEORV32-specific (custom) interrupts --

  constant trap_firq0_c : std_ulogic_vector(5 downto 0) := "1" & "10000"; -- 1.16: fast interrupt 0

  constant trap_firq1_c : std_ulogic_vector(5 downto 0) := "1" & "10001"; -- 1.17: fast interrupt 1

  constant trap_firq2_c : std_ulogic_vector(5 downto 0) := "1" & "10010"; -- 1.18: fast interrupt 2

  constant trap_firq3_c : std_ulogic_vector(5 downto 0) := "1" & "10011"; -- 1.19: fast interrupt 3

  -- CPU Control Exception System -----------------------------------------------------------

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

  -- exception source bits --

  constant exception_iaccess_c   : natural := 0; -- instrution access fault

  constant exception_iillegal_c  : natural := 1; -- illegal instrution

  constant exception_ialign_c    : natural := 2; -- instrution address misaligned

  constant exception_m_envcall_c : natural := 3; -- ENV call from m-mode

  constant exception_break_c     : natural := 4; -- breakpoint

  constant exception_salign_c    : natural := 5; -- store address misaligned

  constant exception_lalign_c    : natural := 6; -- load address misaligned

  constant exception_saccess_c   : natural := 7; -- store access fault

  constant exception_laccess_c   : natural := 8; -- load access fault

  --

  constant exception_width_c     : natural := 9; -- length of this list in bits

  -- interrupt source bits --

  constant interrupt_msw_irq_c   : natural := 0; -- machine software interrupt

  constant interrupt_mtime_irq_c : natural := 1; -- machine timer interrupt

  constant interrupt_mext_irq_c  : natural := 2; -- machine external interrupt

  constant interrupt_firq_0_c    : natural := 3; -- fast interrupt channel 0

  constant interrupt_firq_1_c    : natural := 4; -- fast interrupt channel 1

  constant interrupt_firq_2_c    : natural := 5; -- fast interrupt channel 2

  constant interrupt_firq_3_c    : natural := 6; -- fast interrupt channel 3

  --

  constant interrupt_width_c     : natural := 7; -- length of this list in bits

  -- CPU Privilege Modes --------------------------------------------------------------------

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

  constant priv_mode_m_c : std_ulogic_vector(1 downto 0) := "11"; -- machine mode

  constant priv_mode_u_c : std_ulogic_vector(1 downto 0) := "00"; -- user mode

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

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

  constant clk_div2_c    : natural := 0;

  constant clk_div4_c    : natural := 1;

  constant clk_div8_c    : natural := 2;

  constant clk_div64_c   : natural := 3;

  constant clk_div128_c  : natural := 4;