Subversion Repositories open8_urisc

-- Copyright (c)2006,2011,2012,2013,2015,2020 Jeremy Seth Henry

-- All rights reserved.

--

-- Redistribution and use in source and binary forms, with or without

-- modification, are permitted provided that the following conditions are met:

--     * Redistributions of source code must retain the above copyright

--       notice, this list of conditions and the following disclaimer.

--     * 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,

--       where applicable (as part of a user interface, debugging port, etc.)

--

-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``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 JEREMY SETH HENRY 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 AND

-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-- VHDL Units :  Open8_pkg

-- Description:  Contains constant definitions for the Open8 processor

--

-- Revision History

-- Author          Date     Change

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

-- Seth Henry      07/22/06 Design Start

-- Seth Henry      02/03/12 Updated generics to match current model

-- Seth Henry      10/29/15 Migrated type/constant definitions to this file

-- Seth Henry      03/09/20 Created new ALU/SP opcodes for handling new RSP

-- Seth Henry      03/12/20 Rationalized the naming of the CPU flags to match

--                           the assembler names. Also removed superfluous

--                           signals in the ALU and PC records.

-- Seth Henry      03/17/20 Added new subtype and constants for external

--                           GP flags.

-- Seth Henry      03/18/20 Added the ceil_log2 function, since it is used in

--                           memory sizing calculations.

-- Seth Henry      04/09/20 Added the I bit to the exported flags for use in

--                           memory protection schemes.

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

package Open8_pkg is

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

-- External constants and type declarations

--

-- These subtypes can be used with external peripherals to simplify

--  connection to the core.

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

  -- These must never be changed, as the core requires them to be these static

  --  values for proper operation. These are ONLY defined here to allow user

  --  code to dynamically configure itself to match the Open8 core.

  constant OPEN8_ADDR_WIDTH  : integer := 16; -- DON'T EVEN CONTEMPLATE

  constant OPEN8_DATA_WIDTH  : integer := 8;  -- CHANGING THESE!

  subtype ADDRESS_TYPE is std_logic_vector(OPEN8_ADDR_WIDTH - 1 downto 0);

  subtype DATA_TYPE    is std_logic_vector(OPEN8_DATA_WIDTH - 1 downto 0);

  -- Note: INTERRUPT_BUNDLE must be exactly the same width as DATA_TYPE

  subtype INTERRUPT_BUNDLE is DATA_TYPE;

  subtype EXT_GP_FLAGS is std_logic_vector(4 downto 0);

  constant EXT_ISR           : integer := 0;

  constant EXT_GP4           : integer := 1;

  constant EXT_GP5           : integer := 2;

  constant EXT_GP6           : integer := 3;

  constant EXT_GP7           : integer := 4;

  constant OPEN8_NULLBUS     : DATA_TYPE := x"00";

  type OPEN8_BUS_TYPE is record

    Address                  : ADDRESS_TYPE;

    Wr_En                    : std_logic;

    Wr_Data                  : DATA_TYPE;

    Rd_En                    : std_logic;

  end record;

  -- Component declaration

  --  (assumes a 1K RAM at 0x0000 and ROM at the top of the memory map)

  component o8_cpu is

  generic(

    Program_Start_Addr       : ADDRESS_TYPE := x"8000";

    ISR_Start_Addr           : ADDRESS_TYPE := x"FFF0";

    Stack_Start_Addr         : ADDRESS_TYPE := x"03FF";

    Allow_Stack_Address_Move : boolean      := false;

    Stack_Xfer_Flag          : integer      := 4;

    Enable_Auto_Increment    : boolean      := false;

    BRK_Implements_WAI       : boolean      := false;

    Enable_NMI               : boolean      := true;

    RTI_Ignores_GP_Flags     : boolean      := false;

    Default_Interrupt_Mask   : DATA_TYPE    := x"FF";

    Reset_Level              : std_logic    := '0' );

  port(

    Clock                    : in  std_logic;

    Reset                    : in  std_logic;

    CPU_Halt                 : in  std_logic;

    GP_Flags                 : out EXT_GP_FLAGS;

    Open8_Bus                : out OPEN8_BUS_TYPE;

    Rd_Data                  : in  DATA_TYPE;

    Interrupts               : in  INTERRUPT_BUNDLE

  );

  end component;

  -- This function is used to calculate RAM parameters, but is generally

  --  useful for making things more generic.

  function ceil_log2 (x : in natural) return natural;

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

-- Internal constants and type declarations.

--

-- These are only used in the actual model, and aren't generally useful for

--  external application.

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

  subtype OPCODE_TYPE  is std_logic_vector(4 downto 0);

  subtype SUBOP_TYPE   is std_logic_vector(2 downto 0);

  -- All opcodes should be identical to the opcode used by the assembler

  -- In this case, they match the original V8/ARC uRISC ISA

  constant OP_INC            : OPCODE_TYPE := "00000";

  constant OP_ADC            : OPCODE_TYPE := "00001";

  constant OP_TX0            : OPCODE_TYPE := "00010";

  constant OP_OR             : OPCODE_TYPE := "00011";

  constant OP_AND            : OPCODE_TYPE := "00100";

  constant OP_XOR            : OPCODE_TYPE := "00101";

  constant OP_ROL            : OPCODE_TYPE := "00110";

  constant OP_ROR            : OPCODE_TYPE := "00111";

  constant OP_DEC            : OPCODE_TYPE := "01000";

  constant OP_SBC            : OPCODE_TYPE := "01001";

  constant OP_ADD            : OPCODE_TYPE := "01010";

  constant OP_STP            : OPCODE_TYPE := "01011";

  constant OP_BTT            : OPCODE_TYPE := "01100";

  constant OP_CLP            : OPCODE_TYPE := "01101";

  constant OP_T0X            : OPCODE_TYPE := "01110";

  constant OP_CMP            : OPCODE_TYPE := "01111";

  constant OP_PSH            : OPCODE_TYPE := "10000";

  constant OP_POP            : OPCODE_TYPE := "10001";

  constant OP_BR0            : OPCODE_TYPE := "10010";

  constant OP_BR1            : OPCODE_TYPE := "10011";

  constant OP_DBNZ           : OPCODE_TYPE := "10100"; -- USR

  constant OP_INT            : OPCODE_TYPE := "10101";

  constant OP_MUL            : OPCODE_TYPE := "10110"; -- USR2

  constant OP_STK            : OPCODE_TYPE := "10111";

  constant OP_UPP            : OPCODE_TYPE := "11000";

  constant OP_STA            : OPCODE_TYPE := "11001";

  constant OP_STX            : OPCODE_TYPE := "11010";

  constant OP_STO            : OPCODE_TYPE := "11011";

  constant OP_LDI            : OPCODE_TYPE := "11100";

  constant OP_LDA            : OPCODE_TYPE := "11101";

  constant OP_LDX            : OPCODE_TYPE := "11110";

  constant OP_LDO            : OPCODE_TYPE := "11111";

  -- OP_STK uses the lower 3 bits to further refine the instruction by

  --  repurposing the source register field. These "sub opcodes" take

  --  the place of the register select for the OP_STK opcode

  constant SOP_RSP           : SUBOP_TYPE := "000";

  constant SOP_RTS           : SUBOP_TYPE := "001";

  constant SOP_RTI           : SUBOP_TYPE := "010";

  constant SOP_BRK           : SUBOP_TYPE := "011";

  constant SOP_JMP           : SUBOP_TYPE := "100";

  constant SOP_SMSK          : SUBOP_TYPE := "101";

  constant SOP_GMSK          : SUBOP_TYPE := "110";

  constant SOP_JSR           : SUBOP_TYPE := "111";

  type CPU_STATES is (

      -- Instruction fetch & Decode

    IPF_C0, IPF_C1, IPF_C2, IDC_C0,

    -- Branching

    BRN_C1, DBNZ_C1, JMP_C1, JMP_C2,

    -- Loads

    LDA_C1, LDA_C2, LDA_C3, LDA_C4, LDI_C1,

    LDO_C1, LDX_C1, LDX_C2, LDX_C3, LDX_C4,

    -- Stores

    STA_C1, STA_C2, STA_C3, STO_C1, STO_C2, STX_C1, STX_C2,

    -- 2-cycle math

    MUL_C1, UPP_C1,

    -- Stack

    PSH_C1, POP_C1, POP_C2, POP_C3, POP_C4,

    -- Subroutines & Interrupts

    WAI_Cx, WAH_Cx, BRK_C1,

    ISR_C1, ISR_C2, ISR_C3, JSR_C1, JSR_C2,

    RTS_C1, RTS_C2, RTS_C3, RTS_C4, RTS_C5, RTI_C6

     );

  type CACHE_MODES is (CACHE_IDLE, CACHE_INSTR, CACHE_OPER1, CACHE_OPER2,

                       CACHE_PREFETCH );

  type PC_MODES is ( PC_INCR, PC_LOAD );

  type PC_CTRL_TYPE is record

    Oper                     : PC_MODES;

    Offset                   : DATA_TYPE;

  end record;

  -- These are fixed constant offsets to the program counter logic, which is

  --  always either incrementing or loading.

  constant PC_NEXT           : DATA_TYPE := x"03";

  constant PC_IDLE           : DATA_TYPE := x"02";

  constant PC_REV1           : DATA_TYPE := x"01";

  constant PC_REV2           : DATA_TYPE := x"00";

  constant PC_REV3           : DATA_TYPE := x"FF";

  type SP_MODES is ( SP_IDLE, SP_CLR, SP_SET, SP_POP, SP_PUSH );

  type SP_CTRL_TYPE is record

    Oper                     : SP_MODES;

  end record;

  type DP_MODES is ( DATA_BUS_IDLE, DATA_RD_MEM,

                     DATA_WR_REG, DATA_WR_FLAG, DATA_WR_PC );

  type DATA_CTRL_TYPE is record

    Src                      : DP_MODES;

    Reg                      : SUBOP_TYPE;

  end record;

  constant PC_LSB            : SUBOP_TYPE := "000";

  constant PC_MSB            : SUBOP_TYPE := "001";

  type INT_CTRL_TYPE is record

    Mask_Set                 : std_logic;

    Soft_Ints                : INTERRUPT_BUNDLE;

    Incr_ISR                 : std_logic;

  end record;

  -- Most of the ALU instructions are the same as their Opcode equivalents,

  --  with exceptions for IDLE, UPP2, RFLG, RSP, and GMSK, which perform

  --  internal operations not otherwise exposed by the instruction set.

  constant ALU_INC           : OPCODE_TYPE := "00000"; -- x"00"

  constant ALU_ADC           : OPCODE_TYPE := "00001"; -- x"01"

  constant ALU_TX0           : OPCODE_TYPE := "00010"; -- x"02"

  constant ALU_OR            : OPCODE_TYPE := "00011"; -- x"03"

  constant ALU_AND           : OPCODE_TYPE := "00100"; -- x"04"

  constant ALU_XOR           : OPCODE_TYPE := "00101"; -- x"05"

  constant ALU_ROL           : OPCODE_TYPE := "00110"; -- x"06"

  constant ALU_ROR           : OPCODE_TYPE := "00111"; -- x"07"

  constant ALU_DEC           : OPCODE_TYPE := "01000"; -- x"08"

  constant ALU_SBC           : OPCODE_TYPE := "01001"; -- x"09"

  constant ALU_ADD           : OPCODE_TYPE := "01010"; -- x"0A"

  constant ALU_STP           : OPCODE_TYPE := "01011"; -- x"0B"

  constant ALU_BTT           : OPCODE_TYPE := "01100"; -- x"0C"

  constant ALU_CLP           : OPCODE_TYPE := "01101"; -- x"0D"

  constant ALU_T0X           : OPCODE_TYPE := "01110"; -- x"0E"

  constant ALU_CMP           : OPCODE_TYPE := "01111"; -- x"0F"

  constant ALU_POP           : OPCODE_TYPE := "10001"; -- x"11"

  constant ALU_MUL           : OPCODE_TYPE := "10110"; -- x"16"

  constant ALU_UPP           : OPCODE_TYPE := "11000"; -- x"18"

  constant ALU_LDI           : OPCODE_TYPE := "11100"; -- x"1C"

  constant ALU_IDLE          : OPCODE_TYPE := "10000"; -- x"10"

  constant ALU_UPP2          : OPCODE_TYPE := "10010"; -- x"12"

  constant ALU_RFLG          : OPCODE_TYPE := "10011"; -- x"13"

  constant ALU_RSP           : OPCODE_TYPE := "10111"; -- x"17"

  constant ALU_GMSK          : OPCODE_TYPE := "11111"; -- x"1F"

  -- These should match the assembler's definitions for the flags

  constant PSR_Z             : integer := 0;

  constant PSR_C             : integer := 1;

  constant PSR_N             : integer := 2;

  constant PSR_I             : integer := 3;

  constant PSR_GP4           : integer := 4;

  constant PSR_GP5           : integer := 5;

  constant PSR_GP6           : integer := 6;

  constant PSR_GP7           : integer := 7;

  type ALU_CTRL_TYPE is record

    Oper                     : OPCODE_TYPE;

    Reg                      : SUBOP_TYPE;

  end record;

  constant ACCUM             : SUBOP_TYPE := "000";

  type REGFILE_TYPE is array (0 to 7) of DATA_TYPE;

  subtype FLAG_TYPE is DATA_TYPE;

end Open8_pkg;

package body Open8_pkg is

  -- The ceil_log2 function returns the minimum register width required to

  --  hold the supplied integer.

  function ceil_log2 (x : in natural) return natural is

    variable retval          : natural;

  begin

    retval                   := 1;

    while ((2**retval) - 1) < x loop

      retval                 := retval + 1;

    end loop;

    return retval;

  end ceil_log2;

end package body;