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--

-- PIC16xx compatible microcontroller core

--

-- Version : 0224

--

-- Copyright (c) 2001-2002 Daniel Wallner (jesus@opencores.org)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised 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 synthesized 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.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED 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.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/cvsweb.shtml/ppx16/

--

-- Limitations :

--      Registers implemented in this entity are INDF, PCL, STATUS, FSR, (PCLATH)

--      other registers must be implemented externally including GPR

--

-- File history :

--

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

use work.PPX_Pack.all;

entity PPX16 is

        generic(

                InstructionLength       : integer;

                ROMAddressWidth         : integer;

                StackAddrWidth          : integer;

                TopBoot                         : boolean

        );

        port(

                Clk                     : in std_logic;

                Reset_n         : in std_logic;

                ROM_Addr        : out std_logic_vector(ROMAddressWidth - 1 downto 0);

                ROM_Data        : in std_logic_vector(InstructionLength - 1 downto 0);

                Int_Trig        : in std_logic;

                GIE                     : in std_logic;

                Int_Acc         : out std_logic;

                Int_Ret         : out std_logic;

                File_Addr       : out std_logic_vector(InstructionLength - 6 downto 0);

                File_Addr_r     : out std_logic_vector(InstructionLength - 6 downto 0);

                File_Wr         : out std_logic;

                W_Wr            : out std_logic;

                Instruction     : out std_logic_vector(InstructionLength - 1 downto 0);

                Op_Bus          : in std_logic_vector(7 downto 0);

                W                       : out std_logic_vector(7 downto 0);

                STATUS          : out std_logic_vector(7 downto 0);

                FSR                     : out std_logic_vector(7 downto 0);

                PCLATH          : out std_logic_vector(4 downto 0);

                Res_Bus         : out std_logic_vector(7 downto 0)

        );

end PPX16;

architecture rtl of PPX16 is

        -- File control

        signal  File_Addr_i             : std_logic_vector(InstructionLength - 6 downto 0);

        signal  File_Addr_i_r   : std_logic_vector(InstructionLength - 6 downto 0);

        signal  File_Wr_i               : std_logic;

        signal  PC_CS                   : std_logic;

        -- Registers

        signal  W_i                             : std_logic_vector(7 downto 0);

        signal  PCLATH_i                : std_logic_vector(4 downto 0);

        signal  STATUS_i                : std_logic_vector(7 downto 0);

        signal  FSR_i                   : std_logic_vector(7 downto 0);

        signal  NPC                             : std_logic_vector(InstructionLength - 2 downto 0);

        -- Registered instruction word

        signal  Inst                    : std_logic_vector(InstructionLength - 1 downto 0);

        -- Control signals

        signal  Res_Bus_i               : std_logic_vector(7 downto 0);

        signal  Q                               : std_logic_vector(7 downto 0);

        signal  Op_Mux                  : std_logic_vector(7 downto 0);

        signal  STATUS_d_i              : std_logic_vector(7 downto 0);

        signal  STATUS_d                : std_logic_vector(2 downto 0);

        signal  STATUS_Wr               : std_logic_vector(2 downto 0);

        signal  Z_Skip                  : std_logic;

        signal  B_Skip                  : std_logic;

        signal  Inst_Skip               : std_logic;

        signal  W_Wr_i                  : std_logic;

        signal  Imm_Op                  : std_logic;

        signal  Push                    : std_logic;

        signal  Pop                             : std_logic;

        signal  Goto                    : std_logic;

        signal  IRet                    : std_logic;

        signal  A2Res                   : std_logic;

        signal  B2Res                   : std_logic;

        signal  Sleep                   : std_logic;

        signal  Sleep_r                 : std_logic;

        signal  Int                             : std_logic;

        signal  Int_Pending             : std_logic;

begin

        Int_Acc <= Int;

        W_Wr <= W_Wr_i;

        W <= W_i;

        STATUS <= STATUS_d_i;

        PCLATH <= PCLATH_i;

        FSR <= FSR_i;

        -- Instruction register

        Instruction <= Inst;

        process (Reset_n, Clk)

        begin

                if Reset_n = '0' then

                        Inst <= (others => '0'); -- Force NOP at reset.

                elsif Clk'event and Clk = '1' then

                        if Inst_Skip = '1' then

                                Inst <= (others => '0'); -- Flush (Force NOP)

                        else

                                Inst <= ROM_Data;

                        end if;

                end if;

        end process;

        -- File address

        File_Addr <= File_Addr_i;

        i12 : if InstructionLength = 12 generate

                File_Addr_i <= FSR_i(6 downto 0) when

-- pragma translate_off

                                        is_x(ROM_Data) or

-- pragma translate_on

                                        unsigned(ROM_Data(4 downto 0)) = 0 else

                                        FSR_i(6 downto 5) & ROM_Data(4 downto 0);

        end generate;

        i14 : if InstructionLength = 14 generate

                File_Addr_i <= STATUS_i(7) & FSR_i(7 downto 0) when

-- pragma translate_off

                                        is_x(ROM_Data) or

-- pragma translate_on

                                        unsigned(ROM_Data(6 downto 0)) = 0 else

                                        STATUS_i(6 downto 5) & ROM_Data(6 downto 0);

        end generate;

        process (Clk)

        begin

                if Clk'event and Clk = '1' then

                        File_Addr_r <= File_Addr_i;

                        File_Addr_i_r <= File_Addr_i;

                end if;

        end process;

        -- PCLATH Register

        process (Reset_n, Clk)

        begin

                if Reset_n = '0' then

                        PCLATH_i <= "00000";

                elsif Clk'event and Clk = '1' then

                        if to_integer(unsigned(File_Addr_i_r(6 downto 0))) = 10 and File_Wr_i = '1' then

                                PCLATH_i <= Res_Bus_i(4 downto 0);

                        end if;

                end if;

        end process;

        -- Working register

        process (Clk)

        begin

                if Clk'event and Clk = '1' then

                        if W_Wr_i = '1' then

                                W_i <= Res_Bus_i;

                        end if;

                end if;

        end process;

        -- Status register

        process (STATUS_Wr, STATUS_d, STATUS_i, A2Res, Op_Bus)

        begin

                STATUS_d_i <= STATUS_i;

                if STATUS_Wr(0) = '1' then

                        STATUS_d_i(0) <= STATUS_d(0);

                end if;

                if STATUS_Wr(1) = '1' then

                        STATUS_d_i(1) <= STATUS_d(1);

                end if;

                if STATUS_Wr(2) = '1' then

                        STATUS_d_i(2) <= STATUS_d(2);

                end if;

                if A2Res = '1' then

                        STATUS_d_i(2) <= '0';

                        if Op_Bus = "00000000" then

                                STATUS_d_i(2) <= '1';

                        end if;

                end if;

        end process;

        process (Reset_n, Clk)

        begin

                if Reset_n = '0' then

                        STATUS_i <= "00011000";

                elsif Clk'event and Clk = '1' then

                        if to_integer(unsigned(File_Addr_i_r(InstructionLength - 8 downto 0))) = 3 and

                                File_Wr_i = '1' then

                                STATUS_i <= Res_Bus_i;

                        else

                                STATUS_i <= STATUS_d_i;

                        end if;

                end if;

        end process;

        -- FSR Register

        process (Reset_n, Clk)

        begin

                if Reset_n = '0' then

                        FSR_i <= "11111111";

                elsif Clk'event and Clk = '1' then

                        if to_integer(unsigned(File_Addr_i_r(InstructionLength - 8 downto 0))) = 4 and

                                File_Wr_i = '1' then

                                FSR_i <= Res_Bus_i;

                        end if;

                end if;

        end process;

        -- Program counter

        PC_CS <= '1' when to_integer(unsigned(File_Addr_i_r(InstructionLength - 8 downto 0))) = 2 else '0';

        ROM_Addr <= NPC(ROMAddressWidth - 1 downto 0);

        pcs : PPX_PCS

                generic map(

                        PC_Width => InstructionLength - 1,

                        StackAddrWidth => StackAddrWidth,

                        TopBoot => TopBoot)

                port map(

                        Clk => Clk,

                        Reset_n => Reset_n,

                        CS => PC_CS,

                        Wr => File_Wr_i,

                        Data_In => Res_Bus_i,

                        Addr_In => Inst(InstructionLength - 4 downto 0),

                        PCLATH => PCLATH_i,

                        STATUS => STATUS_i(6 downto 5),

                        NPC => NPC,

                        Int => Int,

                        Sleep => Sleep_r,

                        Push => Push,

                        Pop => Pop,

                        Goto => Goto);

        -- ALU

        Op_Mux <= Inst(7 downto 0) when Imm_Op = '1' else W_i;

        Res_Bus <= Res_Bus_i;

        Res_Bus_i <= Op_Bus when A2Res = '1' else Op_Mux when B2Res = '1' else Q;

        alu : PPX_ALU

                generic map(InstructionLength => InstructionLength)

                port map(

                        Clk => Clk,

                        ROM_Data => ROM_Data,

                        A => Op_Bus,

                        B => Op_Mux,

                        Q => Q,

                        Skip => Inst_Skip,

                        Carry => STATUS_i(0),

                        Z_Skip => Z_Skip,

                        STATUS_d => STATUS_d,

                        STATUS_Wr => STATUS_Wr);

        -- Instruction decoder

        File_Wr <= File_Wr_i;

        Inst_Skip <= Z_Skip or B_Skip or Sleep_r or Int_Pending;

        id : PPX_Ctrl

                generic map(InstructionLength => InstructionLength)

                port map(

                        Clk => Clk,

                        Reset_n => Reset_n,

                        ROM_Data => ROM_Data,

                        Inst => Inst,

                        Skip => Inst_Skip,

                        File_Wr => File_Wr_i,

                        W_Wr => W_Wr_i,

                        Imm_Op => Imm_Op,

                        A2Res => A2Res,

                        B2Res => B2Res,

                        Push => Push,

                        Pop => Pop,

                        Goto => Goto,

                        IRet => IRet,

                        B_Skip => B_Skip,

                        Sleep => Sleep);

        -- Interrupt

        process (Reset_n, Clk)

        begin

                if Reset_n = '0' then

                        Sleep_r <= '0';

                        Int <= '0';

                        Int_Pending <= '0';

                        Int_Ret <= '0';

                elsif Clk'event and Clk = '1' then

                        if Sleep = '1' then

                                Sleep_r <= '1';

                        end if;

                        if Int_Trig = '1' then

                                Sleep_r <= '0';

                        end if;

                        Int_Pending <= '0';

                        Int <= '0';

                        if Int_Trig = '1' and GIE = '1' and Int = '0' then

                                Int_Pending <= '1';

                        end if;

                        if Int_Pending = '1' and Int = '0' and (Z_Skip or B_Skip or Sleep_r) = '0' then

                                Int <= '1';

                        end if;

                        if IRet = '1' then

                                Int_Ret <= '1';

                        else

                                Int_Ret <= '0';

                        end if;

                end if;

        end process;

end;