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--

-- Z80 compatible microprocessor core

--

-- Version : 0238

--

-- 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/t80/

--

-- Limitations :

--      No extra I/O waitstate

--      GB instruction set is incomplete

--      Not all instruction timing are correct

--

-- File history :

--

--      0208 : First complete release

--

--      0210 : Fixed wait and halt

--

--      0211 : Fixed Refresh addition and IM 1

--

--      0214 : Fixed mostly flags, only the block instructions now fail the zex regression test

--

--      0232 : Removed refresh address output for Mode > 1 and added DJNZ M1_n fix by Mike Johnson

--

--      0235 : Added clock enable and IM 2 fix by Mike Johnson

--

--      0237 : Changed 8080 I/O address output, added IntE output

--

--      0238 : Fixed (IX/IY+d) timing and 16 bit ADC and SBC zero flag

--

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

use work.T80_Pack.all;

entity T80 is

        generic(

                Mode : integer := 0      -- 0 => Z80, 1 => Fast Z80, 2 => 8080, 3 => GB

        );

        port(

                RESET_n         : in std_logic;

                CLK_n           : in std_logic;

                CEN                     : in std_logic;

                WAIT_n          : in std_logic;

                INT_n           : in std_logic;

                NMI_n           : in std_logic;

                BUSRQ_n         : in std_logic;

                M1_n            : out std_logic;

                IORQ            : out std_logic;

                NoRead          : out std_logic;

                Write           : out std_logic;

                RFSH_n          : out std_logic;

                HALT_n          : out std_logic;

                BUSAK_n         : out std_logic;

                A                       : out std_logic_vector(15 downto 0);

                DInst           : in std_logic_vector(7 downto 0);

                DI                      : in std_logic_vector(7 downto 0);

                DO                      : out std_logic_vector(7 downto 0);

                MC                      : out std_logic_vector(2 downto 0);

                TS                      : out std_logic_vector(2 downto 0);

                False_M1        : out std_logic;

                IntCycle_n      : out std_logic;

                IntE            : out std_logic

        );

end T80;

architecture rtl of T80 is

        constant Flag_C : integer := 0;

        constant Flag_N : integer := 1;

        constant Flag_P : integer := 2;

        constant Flag_X : integer := 3;

        constant Flag_H : integer := 4;

        constant Flag_Y : integer := 5;

        constant Flag_Z : integer := 6;

        constant Flag_S : integer := 7;

        -- Registers

        signal ACC, F, B, C, D, E, H, L : std_logic_vector(7 downto 0);

        signal Ap, Fp, Bp, Cp, Dp, Ep, Hp, Lp : std_logic_vector(7 downto 0);

        signal I                                : std_logic_vector(7 downto 0);

        signal R                                : unsigned(7 downto 0);

        signal IX, IY                   : std_logic_vector(15 downto 0);

        signal SP, PC                   : unsigned(15 downto 0);

        -- Help Registers

        signal TmpAddr                  : std_logic_vector(15 downto 0); -- Temporary address register

        signal IR                               : std_logic_vector(7 downto 0);          -- Instruction register

        signal ISet                             : std_logic_vector(1 downto 0);          -- Instruction set selector

        signal TState                   : unsigned(2 downto 0);

        signal MCycle                   : std_logic_vector(2 downto 0);

        signal BReq_FF                  : std_logic;

        signal IntE_FF1                 : std_logic;

        signal IntE_FF2                 : std_logic;

        signal Halt_FF                  : std_logic;

        signal NMI_s                    : std_logic;

        signal INT_s                    : std_logic;

        signal IStatus                  : std_logic_vector(1 downto 0);

        signal DI_Reg                   : std_logic_vector(7 downto 0);

        signal T_Res                    : std_logic;

        signal XY_State                 : std_logic_vector(1 downto 0);

        signal XY_Fetch                 : std_logic_vector(1 downto 0);

        signal NextIs_XY_Fetch  : std_logic;

        signal XY_Ind                   : std_logic;

        -- ALU signals

        signal BusB                             : std_logic_vector(7 downto 0);

        signal BusA                             : std_logic_vector(7 downto 0);

        signal ALU_Q                    : std_logic_vector(7 downto 0);

        signal F_Out                    : std_logic_vector(7 downto 0);

        signal F_Save                   : std_logic_vector(7 downto 0);

        -- Registered micro code outputs

        signal Read_To_Reg_r    : std_logic_vector(4 downto 0);

        signal Arith16_r                : std_logic;

        signal Z16_r                    : std_logic;

        signal ALU_Op_r                 : std_logic_vector(3 downto 0);

        signal AALU_OP_r                : std_logic_vector(2 downto 0);

        signal Rot_Op_r                 : std_logic;

        signal Bit_Op_r                 : std_logic_vector(1 downto 0);

        signal Save_ALU_r               : std_logic;

        signal PreserveC_r              : std_logic;

        signal MCycles                  : std_logic_vector(2 downto 0);

        -- Micro code outputs

        signal MCycles_d                : std_logic_vector(2 downto 0);

        signal TStates                  : std_logic_vector(2 downto 0);

        signal IntCycle                 : std_logic;

        signal NMICycle                 : std_logic;

        signal Inc_PC                   : std_logic;

        signal Inc_WZ                   : std_logic;

        signal IncDec_16                : std_logic_vector(3 downto 0);

        signal Prefix                   : std_logic_vector(1 downto 0);

        signal Read_To_Acc              : std_logic;

        signal Read_To_Reg              : std_logic;

        signal Set_BusB_To              : std_logic_vector(3 downto 0);

        signal Set_BusA_To              : std_logic_vector(3 downto 0);

        signal ALU_Op                   : std_logic_vector(3 downto 0);

        signal Rot_Op                   : std_logic;

        signal Bit_Op                   : std_logic_vector(1 downto 0);

        signal Save_ALU                 : std_logic;

        signal PreserveC                : std_logic;

        signal Arith16                  : std_logic;

        signal Set_Addr_To              : AddressOutput;

        signal Jump                             : std_logic;

        signal JumpE                    : std_logic;

        signal JumpXY                   : std_logic;

        signal Call                             : std_logic;

        signal RstP                             : std_logic;

        signal LDZ                              : std_logic;

        signal LDW                              : std_logic;

        signal LDSPHL                   : std_logic;

        signal Special_LD               : std_logic_vector(2 downto 0);

        signal ExchangeDH               : std_logic;

        signal ExchangeRp               : std_logic;

        signal ExchangeAF               : std_logic;

        signal ExchangeRS               : std_logic;

        signal I_DJNZ                   : std_logic;

        signal I_CPL                    : std_logic;

        signal I_CCF                    : std_logic;

        signal I_SCF                    : std_logic;

        signal I_RETN                   : std_logic;

        signal I_BT                             : std_logic;

        signal I_BC                             : std_logic;

        signal I_BTR                    : std_logic;

        signal I_RLD                    : std_logic;

        signal I_RRD                    : std_logic;

        signal I_INRC                   : std_logic;

        signal SetDI                    : std_logic;

        signal SetEI                    : std_logic;

        signal IMode                    : std_logic_vector(1 downto 0);

        signal Halt                             : std_logic;

begin

        IntE <= IntE_FF1;

        mcode : T80_MCode

                generic map(

                        Mode => Mode)

                port map(

                        IR => IR,

                        ISet => ISet,

                        MCycle => MCycle,

                        F => F,

                        NMICycle => NMICycle,

                        IntCycle => IntCycle,

                        MCycles => MCycles_d,

                        TStates => TStates,

                        Prefix => Prefix,

                        Inc_PC => Inc_PC,

                        Inc_WZ => Inc_WZ,

                        IncDec_16 => IncDec_16,

                        Read_To_Acc => Read_To_Acc,

                        Read_To_Reg => Read_To_Reg,

                        Set_BusB_To => Set_BusB_To,

                        Set_BusA_To => Set_BusA_To,

                        ALU_Op => ALU_Op,

                        Rot_Op => Rot_Op,

                        Bit_Op => Bit_Op,

                        Save_ALU => Save_ALU,

                        PreserveC => PreserveC,

                        Arith16 => Arith16,

                        Set_Addr_To => Set_Addr_To,

                        IORQ => IORQ,

                        Jump => Jump,

                        JumpE => JumpE,

                        JumpXY => JumpXY,

                        Call => Call,

                        RstP => RstP,

                        LDZ => LDZ,

                        LDW => LDW,

                        LDSPHL => LDSPHL,

                        Special_LD => Special_LD,

                        ExchangeDH => ExchangeDH,

                        ExchangeRp => ExchangeRp,

                        ExchangeAF => ExchangeAF,

                        ExchangeRS => ExchangeRS,

                        I_DJNZ => I_DJNZ,

                        I_CPL => I_CPL,

                        I_CCF => I_CCF,

                        I_SCF => I_SCF,

                        I_RETN => I_RETN,

                        I_BT => I_BT,

                        I_BC => I_BC,

                        I_BTR => I_BTR,

                        I_RLD => I_RLD,

                        I_RRD => I_RRD,

                        I_INRC => I_INRC,

                        SetDI => SetDI,

                        SetEI => SetEI,

                        IMode => IMode,

                        Halt => Halt,

                        NoRead => NoRead,

                        Write => Write);

        alu : T80_ALU

                port map(

                        Arith16 => Arith16_r,

                        Z16 => Z16_r,

                        ALU_Op => ALU_Op_r,

                        Rot_Op => Rot_Op_r,

                        Bit_Op => Bit_Op_r,

                        IR => IR,

                        ISet => ISet,

                        BusA => BusA,

                        BusB => BusB,

                        F_In => F,

                        Q => ALU_Q,

                        F_Out => F_Out,

                        F_Save => F_Save);

        T_Res <= '1' when (TState = unsigned(TStates) and XY_Fetch(0) = '0') or

                                        (XY_Fetch(0) = '1' and TState = "111" and Mode = 0) or

                                        (XY_Fetch(0) = '1' and TState = "100" and Mode = 1) else '0';

        NextIs_XY_Fetch <= '1' when XY_State /= "00" and XY_Ind = '0' and ((Set_Addr_To = aXY and IR /= "11001011") or

                                                        (MCycle = "001" and IR = "11001011") or

                                                        (MCycle = "001" and IR = "00110110")) else '0';

        process (RESET_n, CLK_n)

                variable ID16           : signed(15 downto 0);

                variable Save_Mux       : std_logic_vector(7 downto 0);

        begin

                if RESET_n = '0' then

                        PC <= (others => '0');  -- Program Counter

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

                        IR <= "00000000";

                        ISet <= "00";

                        XY_State <= "00";

                        IStatus <= "00";

                        ACC <= (others => '1');

                        F <= (others => '1');

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

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

                        SP <= (others => '1');

                        Read_To_Reg_r <= "00000";

                        Arith16_r <= '0';

                        Z16_r <= '0';

                        ALU_Op_r <= "0000";

                        Rot_Op_r <= '0';

                        Bit_Op_r <= "00";

                        Save_ALU_r <= '0';

                        PreserveC_r <= '0';

                        AALU_OP_r <= "000";

                        XY_Ind <= '0';

                elsif CLK_n'event and CLK_n = '1' then

                        if CEN = '1' then

                        ALU_Op_r <= "0000";

                        Rot_Op_r <= '0';

                        Bit_Op_r <= "00";

                        Save_ALU_r <= '0';

                        AALU_OP_r <= "000";

                        Read_To_Reg_r <= "00000";

                        MCycles <= MCycles_d;

                        if IMode /= "11" then

                                IStatus <= IMode;

                        end if;

                        Arith16_r <= Arith16;

                        PreserveC_r <= PreserveC;

                        if ISet = "10" and ALU_OP(2) = '0' and ALU_OP(0) = '1' and MCycle = "011" then

                                Z16_r <= '1';

                        else

                                Z16_r <= '0';

                        end if;

                        if MCycle  = "001" and TState(2) = '0' and XY_Fetch(0) = '0' then

                        -- MCycle = 1 and TState = 1, 2, or 3

                                if TState = 2 and Wait_n = '1' then

                                        if Mode < 2 then

                                                A(7 downto 0) <= std_logic_vector(R);

                                                A(15 downto 8) <= I;

                                                R(6 downto 0) <= R(6 downto 0) + 1;

                                        end if;

                                        if Jump = '0' and Call = '0' and NMICycle = '0' and IntCycle = '0' and not (Halt_FF = '1' or Halt = '1') then

                                                PC <= PC + 1;

                                        end if;

                                        if IntCycle = '1' and IStatus = "01" then

                                                IR <= "11111111";

                                        elsif Halt_FF = '1' or (IntCycle = '1' and IStatus = "10") or NMICycle = '1' then

                                                IR <= "00000000";

                                        else

                                                IR <= DInst;

                                        end if;

                                        ISet <= "00";

                                        if Prefix /= "00" then

                                                if Prefix = "11" then

                                                        if IR(5) = '1' then

                                                                XY_State <= "10";

                                                        else

                                                                XY_State <= "01";

                                                        end if;

                                                else

                                                        if Prefix = "10" then

                                                                XY_State <= "00";

                                                                XY_Ind <= '0';

                                                        end if;

                                                        ISet <= Prefix;

                                                end if;

                                        else

                                                XY_State <= "00";

                                                XY_Ind <= '0';

                                        end if;

                                end if;

                        else

                        -- either (MCycle > 1) OR (MCycle = 1 AND TState > 3)

                                if XY_Fetch(0) = '1' then

                                        XY_Ind <= '1';

                                end if;

                                if T_Res = '1' then

                                        if Jump = '1' then

                                                A(15 downto 8) <= DI_Reg;

                                                A(7 downto 0) <= TmpAddr(7 downto 0);

                                                PC(15 downto 8) <= unsigned(DI_Reg);

                                                PC(7 downto 0) <= unsigned(TmpAddr(7 downto 0));

                                        elsif JumpXY = '1' then

                                                case XY_State is

                                                when "01" =>

                                                        A <= IX;

                                                        PC <= unsigned(IX);

                                                when "10" =>

                                                        A <= IY;

                                                        PC <= unsigned(IY);

                                                when others =>

                                                        A(15 downto 8) <= H;

                                                        A(7 downto 0) <= L;

                                                        PC(15 downto 8) <= unsigned(H);

                                                        PC(7 downto 0) <= unsigned(L);

                                                end case;

                                        elsif Call = '1' or RstP = '1' then

                                                A <= TmpAddr;

                                                PC <= unsigned(TmpAddr);

                                        elsif MCycle = MCycles and NMICycle = '1' then

                                                A <= "0000000001100110";

                                                PC <= "0000000001100110";

                                        elsif MCycle = "011" and IntCycle = '1' and IStatus = "10" then

                                                A(15 downto 8) <= I;

                                                A(7 downto 0) <= TmpAddr(7 downto 0);

                                                PC(15 downto 8) <= unsigned(I);

                                                PC(7 downto 0) <= unsigned(TmpAddr(7 downto 0));

                                        else

                                                case Set_Addr_To is

                                                when aXY =>

                                                        if XY_State = "00" then

                                                                A(15 downto 8) <= H;

                                                                A(7 downto 0) <= L;

                                                        else

                                                                if NextIs_XY_Fetch = '1' then

                                                                        A <= std_logic_vector(PC);

                                                                else

                                                                        A <= TmpAddr;

                                                                end if;

                                                        end if;

                                                when aIOA =>

                                                        if Mode = 2 then

                                                                -- Duplicate I/O address on 8080

                                                                A(15 downto 8) <= DI_Reg;

                                                        else

                                                                A(15 downto 8) <= ACC;

                                                        end if;

                                                        A(7 downto 0) <= DI_Reg;

                                                when aSP =>

                                                        A <= std_logic_vector(SP);

                                                when aBC =>

                                                        A(15 downto 8) <= B;

                                                        A(7 downto 0) <= C;

                                                when aDE =>

                                                        A(15 downto 8) <= D;

                                                        A(7 downto 0) <= E;

                                                when aZI =>

                                                        if Inc_WZ = '1' then

                                                                A <= std_logic_vector(unsigned(TmpAddr) + 1);

                                                        else

                                                                A(15 downto 8) <= DI_Reg;

                                                                A(7 downto 0) <= TmpAddr(7 downto 0);

                                                        end if;

                                                when aNone =>

                                                        A <= std_logic_vector(PC);

                                                end case;

                                        end if;

                                        Save_ALU_r <= Save_ALU;

                                        ALU_Op_r <= ALU_Op;

                                        Rot_Op_r <= Rot_Op;

                                        Bit_Op_r <= Bit_Op;

                                        if Save_ALU = '1' then

                                                if Rot_Op = '0' and Bit_Op = "00" then

                                                        if ALU_Op(3) = '1' then

                                                                AALU_OP_r <= ALU_Op(2 downto 0);

                                                        else

                                                                AALU_OP_r <= IR(5 downto 3);

                                                        end if;

                                                end if;

                                        end if;

                                        if I_CPL = '1' then

                                                -- CPL

                                                ACC <= not ACC;

                                                F(Flag_Y) <= not ACC(5);

                                                F(Flag_H) <= '1';

                                                F(Flag_X) <= not ACC(3);

                                                F(Flag_N) <= '1';

                                        end if;

                                        if I_CCF = '1' then

                                                -- CCF

                                                F(Flag_C) <= not F(Flag_C);

                                                F(Flag_Y) <= ACC(5);

                                                F(Flag_H) <= F(Flag_C);

                                                F(Flag_X) <= ACC(3);

                                                F(Flag_N) <= '0';

                                        end if;

                                        if I_SCF = '1' then

                                                -- SCF

                                                F(Flag_C) <= '1';

                                                F(Flag_Y) <= ACC(5);

                                                F(Flag_H) <= '0';

                                                F(Flag_X) <= ACC(3);

                                                F(Flag_N) <= '0';

                                        end if;

                                end if;

                                if TState = 2 and Wait_n = '1' then

                                        if JumpE = '1' then

                                                PC <= unsigned(signed(PC) + signed(DI_Reg));

                                        elsif Inc_PC = '1' or XY_Fetch(0) = '1' then

                                                PC <= PC + 1;

                                        end if;

                                        if I_BTR = '1' then

                                                PC <= PC - 2;

                                        end if;

                                        if RstP = '1' then

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

                                                TmpAddr(5 downto 3) <= IR(5 downto 3);

                                        end if;

                                end if;

                                if TState = 3 and XY_Fetch = "01" then

                                        if XY_State = "01" then

                                                TmpAddr <= std_logic_vector(signed(IX) + signed(DI_Reg));

                                        end if;

                                        if XY_State = "10" then

                                                TmpAddr <= std_logic_vector(signed(IY) + signed(DI_Reg));

                                        end if;

                                end if;

                                if (TState = 2 and Wait_n = '1') or (TState = 4 and MCycle = "001") then

                                        if IncDec_16 = "1100" then

                                                ID16(15 downto 8) := signed(B);

                                                ID16(7 downto 0) := signed(C);

                                                ID16 := ID16 - 1;

                                                B <= std_logic_vector(ID16(15 downto 8));

                                                C <= std_logic_vector(ID16(7 downto 0));

                                        end if;

                                        if IncDec_16 = "1101" then

                                                ID16(15 downto 8) := signed(D);

                                                ID16(7 downto 0) := signed(E);

                                                ID16 := ID16 - 1;

                                                D <= std_logic_vector(ID16(15 downto 8));

                                                E <= std_logic_vector(ID16(7 downto 0));

                                        end if;

                                        if IncDec_16 = "1110" then

                                                case XY_State is

                                                when "01" =>

                                                        IX <= std_logic_vector(unsigned(IX) - 1);

                                                when "10" =>

                                                        IY <= std_logic_vector(unsigned(IY) - 1);

                                                when others =>

                                                        ID16(15 downto 8) := signed(H);

                                                        ID16(7 downto 0) := signed(L);

                                                        ID16 := ID16 - 1;

                                                        H <= std_logic_vector(ID16(15 downto 8));

                                                        L <= std_logic_vector(ID16(7 downto 0));

                                                end case;

                                        end if;

                                        if IncDec_16 = "1111" then

                                                SP <= SP - 1;

                                        end if;

                                        if IncDec_16 = "0100" then

                                                ID16(15 downto 8) := signed(B);

                                                ID16(7 downto 0) := signed(C);

                                                ID16 := ID16 + 1;

                                                B <= std_logic_vector(ID16(15 downto 8));

                                                C <= std_logic_vector(ID16(7 downto 0));

                                        end if;

                                        if IncDec_16 = "0101" then

                                                ID16(15 downto 8) := signed(D);

                                                ID16(7 downto 0) := signed(E);

                                                ID16 := ID16 + 1;

                                                D <= std_logic_vector(ID16(15 downto 8));

                                                E <= std_logic_vector(ID16(7 downto 0));

                                        end if;

                                        if IncDec_16 = "0110" then

                                                case XY_State is

                                                when "01" =>

                                                        IX <= std_logic_vector(unsigned(IX) + 1);

                                                when "10" =>

                                                        IY <= std_logic_vector(unsigned(IY) + 1);

                                                when others =>

                                                        ID16(15 downto 8) := signed(H);

                                                        ID16(7 downto 0) := signed(L);