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-- ****
-- T80(b) core. In an effort to merge and maintain bug fixes ....
--
--
-- Ver 300 started tidyup. Rmoved some auto_wait bits from 0247 which caused problems
--
-- MikeJ March 2005
-- Latest version from www.fpgaarcade.com (original www.opencores.org)
--
-- ****
--
-- Z80 compatible microprocessor core
--
-- Version : 0247
--
-- 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 :
--
-- 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
--
-- 0240 : Added interrupt ack fix by Mike Johnson, changed (IX/IY+d) timing and changed flags in GB mode
--
-- 0242 : Added I/O wait, fixed refresh address, moved some registers to RAM
--
-- 0247 : Fixed bus req/ack cycle
--
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
IOWait : integer := 0; -- 1 => Single cycle I/O, 1 => Std I/O cycle
Flag_C : integer := 0;
Flag_N : integer := 1;
Flag_P : integer := 2;
Flag_X : integer := 3;
Flag_H : integer := 4;
Flag_Y : integer := 5;
Flag_Z : integer := 6;
Flag_S : integer := 7
);
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);
IntCycle_n : out std_logic;
IntE : out std_logic;
Stop : out std_logic;
ResetPC : in std_logic_vector(15 downto 0);
ResetSP : in std_logic_vector(15 downto 0)
);
end T80;
architecture rtl of T80 is
constant aNone : std_logic_vector(2 downto 0) := "111";
constant aBC : std_logic_vector(2 downto 0) := "000";
constant aDE : std_logic_vector(2 downto 0) := "001";
constant aXY : std_logic_vector(2 downto 0) := "010";
constant aIOA : std_logic_vector(2 downto 0) := "100";
constant aSP : std_logic_vector(2 downto 0) := "101";
constant aZI : std_logic_vector(2 downto 0) := "110";
-- Registers
signal ACC, F : std_logic_vector(7 downto 0);
signal Ap, Fp : std_logic_vector(7 downto 0);
signal I : std_logic_vector(7 downto 0);
signal R : unsigned(7 downto 0);
signal SP, PC : unsigned(15 downto 0);
signal RegDIH : std_logic_vector(7 downto 0);
signal RegDIL : std_logic_vector(7 downto 0);
signal RegBusA : std_logic_vector(15 downto 0);
signal RegBusB : std_logic_vector(15 downto 0);
signal RegBusC : std_logic_vector(15 downto 0);
signal RegAddrA_r : std_logic_vector(2 downto 0);
signal RegAddrA : std_logic_vector(2 downto 0);
signal RegAddrB_r : std_logic_vector(2 downto 0);
signal RegAddrB : std_logic_vector(2 downto 0);
signal RegAddrC : std_logic_vector(2 downto 0);
signal RegWEH : std_logic;
signal RegWEL : std_logic;
signal Alternate : std_logic;
-- 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 RegBusA_r : std_logic_vector(15 downto 0);
signal ID16 : signed(15 downto 0);
signal Save_Mux : std_logic_vector(7 downto 0);
signal TState : unsigned(2 downto 0);
signal MCycle : std_logic_vector(2 downto 0);
signal IntE_FF1 : std_logic;
signal IntE_FF2 : std_logic;
signal Halt_FF : std_logic;
signal BusReq_s : std_logic;
signal BusAck : std_logic;
signal ClkEn : 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 Pre_XY_F_M : std_logic_vector(2 downto 0);
signal NextIs_XY_Fetch : std_logic;
signal XY_Ind : std_logic;
signal No_BTR : std_logic;
signal BTR_r : std_logic;
signal Auto_Wait : std_logic;
signal Auto_Wait_t1 : std_logic;
signal Auto_Wait_t2 : std_logic;
signal IncDecZ : 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);
-- 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 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 Save_ALU : std_logic;
signal PreserveC : std_logic;
signal Arith16 : std_logic;
signal Set_Addr_To : std_logic_vector(2 downto 0);
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 IORQ_i : 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
mcode : T80_MCode
generic map(
Mode => Mode,
Flag_C => Flag_C,
Flag_N => Flag_N,
Flag_P => Flag_P,
Flag_X => Flag_X,
Flag_H => Flag_H,
Flag_Y => Flag_Y,
Flag_Z => Flag_Z,
Flag_S => Flag_S)
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,
Save_ALU => Save_ALU,
PreserveC => PreserveC,
Arith16 => Arith16,
Set_Addr_To => Set_Addr_To,
IORQ => IORQ_i,
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
generic map(
Mode => Mode,
Flag_C => Flag_C,
Flag_N => Flag_N,
Flag_P => Flag_P,
Flag_X => Flag_X,
Flag_H => Flag_H,
Flag_Y => Flag_Y,
Flag_Z => Flag_Z,
Flag_S => Flag_S)
port map(
Arith16 => Arith16_r,
Z16 => Z16_r,
ALU_Op => ALU_Op_r,
IR => IR(5 downto 0),
ISet => ISet,
BusA => BusA,
BusB => BusB,
F_In => F,
Q => ALU_Q,
F_Out => F_Out);
ClkEn <= CEN and not BusAck;
T_Res <= '1' when TState = unsigned(TStates) else '0';
NextIs_XY_Fetch <= '1' when XY_State /= "00" and XY_Ind = '0' and
((Set_Addr_To = aXY) or
(MCycle = "001" and IR = "11001011") or
(MCycle = "001" and IR = "00110110")) else '0';
Save_Mux <= BusB when ExchangeRp = '1' else
DI_Reg when Save_ALU_r = '0' else
ALU_Q;
process (RESET_n, CLK_n)
begin
if RESET_n = '0' then
PC <= unsigned(ResetPC);
-- (others => '0') -- Program Counter
A <= ResetPC; -- (others => '0');
TmpAddr <= (others => '0');
IR <= "00000000";
ISet <= "00";
XY_State <= "00";
IStatus <= "00";
MCycles <= "000";
DO <= "00000000";
ACC <= (others => '1');
F <= (others => '1');
Ap <= (others => '1');
Fp <= (others => '1');
I <= (others => '0');
R <= (others => '0');
SP <= unsigned(ResetSP);
-- (others => '1')
Alternate <= '0';
Read_To_Reg_r <= "00000";
F <= (others => '1');
Arith16_r <= '0';
BTR_r <= '0';
Z16_r <= '0';
ALU_Op_r <= "0000";
Save_ALU_r <= '0';
PreserveC_r <= '0';
XY_Ind <= '0';
elsif CLK_n'event and CLK_n = '1' then
if ClkEn = '1' then
ALU_Op_r <= "0000";
Save_ALU_r <= '0';
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' 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 MCycle = "110" then
XY_Ind <= '1';
if Prefix = "01" then
ISet <= "01";
end if;
end if;
if T_Res = '1' then
BTR_r <= (I_BT or I_BC or I_BTR) and not No_BTR;
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
A <= RegBusC;
PC <= unsigned(RegBusC);
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 <= RegBusC;
else
if NextIs_XY_Fetch = '1' then
A <= std_logic_vector(PC);
else
A <= TmpAddr;
end if;
end if;
when aIOA =>
if Mode = 3 then
-- Memory map I/O on GBZ80
A(15 downto 8) <= (others => '1');
elsif 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 =>
if Mode = 3 and IORQ_i = '1' then
-- Memory map I/O on GBZ80
A(15 downto 8) <= (others => '1');
A(7 downto 0) <= RegBusC(7 downto 0);
else
A <= RegBusC;
end if;
when aDE =>
A <= RegBusC;
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 others =>
A <= std_logic_vector(PC);
end case;
end if;
Save_ALU_r <= Save_ALU;
ALU_Op_r <= ALU_Op;
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 ISet = "01" and MCycle = "111" then
IR <= DInst;
end if;
if JumpE = '1' then
PC <= unsigned(signed(PC) + signed(DI_Reg));
elsif Inc_PC = '1' then
PC <= PC + 1;
end if;
if BTR_r = '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 MCycle = "110" then
TmpAddr <= std_logic_vector(signed(RegBusC) + signed(DI_Reg));
end if;
if (TState = 2 and Wait_n = '1') or (TState = 4 and MCycle = "001") then
if IncDec_16(2 downto 0) = "111" then
if IncDec_16(3) = '1' then
SP <= SP - 1;
else
SP <= SP + 1;
end if;
end if;
end if;
if LDSPHL = '1' then
SP <= unsigned(RegBusC);
end if;
if ExchangeAF = '1' then
Ap <= ACC;
ACC <= Ap;
Fp <= F;
F <= Fp;
end if;
if ExchangeRS = '1' then
Alternate <= not Alternate;
end if;
end if;
if TState = 3 then
if LDZ = '1' then
TmpAddr(7 downto 0) <= DI_Reg;
end if;
if LDW = '1' then
TmpAddr(15 downto 8) <= DI_Reg;
end if;
if Special_LD(2) = '1' then
case Special_LD(1 downto 0) is
when "00" =>
ACC <= I;
F(Flag_P) <= IntE_FF2;
when "01" =>
ACC <= std_logic_vector(R);
F(Flag_P) <= IntE_FF2;
when "10" =>
I <= ACC;
when others =>
R <= unsigned(ACC);
end case;
end if;
end if;
if (I_DJNZ = '0' and Save_ALU_r = '1') or ALU_Op_r = "1001" then
if Mode = 3 then
F(6) <= F_Out(6);
F(5) <= F_Out(5);
F(7) <= F_Out(7);
if PreserveC_r = '0' then
F(4) <= F_Out(4);
end if;
else
F(7 downto 1) <= F_Out(7 downto 1);
if PreserveC_r = '0' then
F(Flag_C) <= F_Out(0);
end if;
end if;
end if;
if T_Res = '1' and I_INRC = '1' then
F(Flag_H) <= '0';
F(Flag_N) <= '0';
if DI_Reg(7 downto 0) = "00000000" then
F(Flag_Z) <= '1';
else
F(Flag_Z) <= '0';
end if;
F(Flag_S) <= DI_Reg(7);
F(Flag_P) <= not (DI_Reg(0) xor DI_Reg(1) xor DI_Reg(2) xor DI_Reg(3) xor
DI_Reg(4) xor DI_Reg(5) xor DI_Reg(6) xor DI_Reg(7));
end if;
if TState = 1 then
DO <= BusB;
if I_RLD = '1' then
DO(3 downto 0) <= BusA(3 downto 0);
DO(7 downto 4) <= BusB(3 downto 0);
end if;
if I_RRD = '1' then
DO(3 downto 0) <= BusB(7 downto 4);
DO(7 downto 4) <= BusA(3 downto 0);
end if;
end if;
if T_Res = '1' then
Read_To_Reg_r(3 downto 0) <= Set_BusA_To;
Read_To_Reg_r(4) <= Read_To_Reg;
if Read_To_Acc = '1' then
Read_To_Reg_r(3 downto 0) <= "0111";
Read_To_Reg_r(4) <= '1';
end if;
end if;
if TState = 1 and I_BT = '1' then
F(Flag_X) <= ALU_Q(3);
F(Flag_Y) <= ALU_Q(1);
F(Flag_H) <= '0';
F(Flag_N) <= '0';
end if;
if I_BC = '1' or I_BT = '1' then
F(Flag_P) <= IncDecZ;
end if;
if (TState = 1 and Save_ALU_r = '0') or
(Save_ALU_r = '1' and ALU_OP_r /= "0111") then
case Read_To_Reg_r is
when "10111" =>
ACC <= Save_Mux;
when "10110" =>
DO <= Save_Mux;
when "11000" =>
SP(7 downto 0) <= unsigned(Save_Mux);
when "11001" =>
SP(15 downto 8) <= unsigned(Save_Mux);
when "11011" =>
F <= Save_Mux;
when others =>
end case;
end if;
end if;
end if;
end process;
---------------------------------------------------------------------------
--
-- BC('), DE('), HL('), IX and IY
--
---------------------------------------------------------------------------
process (CLK_n)
begin
if CLK_n'event and CLK_n = '1' then
if ClkEn = '1' then
-- Bus A / Write
RegAddrA_r <= Alternate & Set_BusA_To(2 downto 1);
if XY_Ind = '0' and XY_State /= "00" and Set_BusA_To(2 downto 1) = "10" then
RegAddrA_r <= XY_State(1) & "11";
end if;
-- Bus B
RegAddrB_r <= Alternate & Set_BusB_To(2 downto 1);
if XY_Ind = '0' and XY_State /= "00" and Set_BusB_To(2 downto 1) = "10" then
RegAddrB_r <= XY_State(1) & "11";
end if;
-- Address from register
RegAddrC <= Alternate & Set_Addr_To(1 downto 0);
-- Jump (HL), LD SP,HL
if (JumpXY = '1' or LDSPHL = '1') then
RegAddrC <= Alternate & "10";
end if;
if ((JumpXY = '1' or LDSPHL = '1') and XY_State /= "00") or (MCycle = "110") then
RegAddrC <= XY_State(1) & "11";
end if;
if I_DJNZ = '1' and Save_ALU_r = '1' and Mode < 2 then
IncDecZ <= F_Out(Flag_Z);
end if;
if (TState = 2 or (TState = 3 and MCycle = "001")) and IncDec_16(2 downto 0) = "100" then
if ID16 = 0 then
IncDecZ <= '0';
else
IncDecZ <= '1';
end if;
end if;
RegBusA_r <= RegBusA;
end if;
end if;
end process;
RegAddrA <=
-- 16 bit increment/decrement
Alternate & IncDec_16(1 downto 0) when (TState = 2 or
(TState = 3 and MCycle = "001" and IncDec_16(2) = '1')) and XY_State = "00" else
XY_State(1) & "11" when (TState = 2 or
(TState = 3 and MCycle = "001" and IncDec_16(2) = '1')) and IncDec_16(1 downto 0) = "10" else
-- EX HL,DL
Alternate & "10" when ExchangeDH = '1' and TState = 3 else
Alternate & "01" when ExchangeDH = '1' and TState = 4 else
-- Bus A / Write
RegAddrA_r;
RegAddrB <=
-- EX HL,DL
Alternate & "01" when ExchangeDH = '1' and TState = 3 else
-- Bus B
RegAddrB_r;
ID16 <= signed(RegBusA) - 1 when IncDec_16(3) = '1' else
signed(RegBusA) + 1;
process (Save_ALU_r, Auto_Wait_t1, ALU_OP_r, Read_To_Reg_r,
ExchangeDH, IncDec_16, MCycle, TState, Wait_n)
begin
RegWEH <= '0';
RegWEL <= '0';
if (TState = 1 and Save_ALU_r = '0') or
(Save_ALU_r = '1' and ALU_OP_r /= "0111") then
case Read_To_Reg_r is
when "10000" | "10001" | "10010" | "10011" | "10100" | "10101" =>
RegWEH <= not Read_To_Reg_r(0);
RegWEL <= Read_To_Reg_r(0);
when others =>
end case;
end if;
if ExchangeDH = '1' and (TState = 3 or TState = 4) then
RegWEH <= '1';
RegWEL <= '1';
end if;
if IncDec_16(2) = '1' and ((TState = 2 and Wait_n = '1' and MCycle /= "001") or (TState = 3 and MCycle = "001")) then
case IncDec_16(1 downto 0) is
when "00" | "01" | "10" =>
RegWEH <= '1';
RegWEL <= '1';
when others =>
end case;
end if;
end process;
process (Save_Mux, RegBusB, RegBusA_r, ID16,
ExchangeDH, IncDec_16, MCycle, TState, Wait_n)
begin
RegDIH <= Save_Mux;
RegDIL <= Save_Mux;
if ExchangeDH = '1' and TState = 3 then
RegDIH <= RegBusB(15 downto 8);
RegDIL <= RegBusB(7 downto 0);
end if;
if ExchangeDH = '1' and TState = 4 then
RegDIH <= RegBusA_r(15 downto 8);
RegDIL <= RegBusA_r(7 downto 0);
end if;
if IncDec_16(2) = '1' and ((TState = 2 and MCycle /= "001") or (TState = 3 and MCycle = "001")) then
RegDIH <= std_logic_vector(ID16(15 downto 8));
RegDIL <= std_logic_vector(ID16(7 downto 0));
end if;
end process;
Regs : T80_Reg
port map(
Clk => CLK_n,
CEN => ClkEn,
WEH => RegWEH,
WEL => RegWEL,
AddrA => RegAddrA,
AddrB => RegAddrB,
AddrC => RegAddrC,
DIH => RegDIH,
DIL => RegDIL,
DOAH => RegBusA(15 downto 8),
DOAL => RegBusA(7 downto 0),
DOBH => RegBusB(15 downto 8),
DOBL => RegBusB(7 downto 0),
DOCH => RegBusC(15 downto 8),
DOCL => RegBusC(7 downto 0));
---------------------------------------------------------------------------
--
-- Buses
--
---------------------------------------------------------------------------
process (CLK_n)
begin
if CLK_n'event and CLK_n = '1' then
if ClkEn = '1' then
case Set_BusB_To is
when "0111" =>
BusB <= ACC;
when "0000" | "0001" | "0010" | "0011" | "0100" | "0101" =>
if Set_BusB_To(0) = '1' then
BusB <= RegBusB(7 downto 0);
else
BusB <= RegBusB(15 downto 8);
end if;
when "0110" =>
BusB <= DI_Reg;
when "1000" =>
BusB <= std_logic_vector(SP(7 downto 0));
when "1001" =>
BusB <= std_logic_vector(SP(15 downto 8));
when "1010" =>
BusB <= "00000001";
when "1011" =>
BusB <= F;
when "1100" =>
BusB <= std_logic_vector(PC(7 downto 0));
when "1101" =>
BusB <= std_logic_vector(PC(15 downto 8));
when "1110" =>
BusB <= "00000000";
when others =>
BusB <= "--------";
end case;
case Set_BusA_To is
when "0111" =>
BusA <= ACC;
when "0000" | "0001" | "0010" | "0011" | "0100" | "0101" =>
if Set_BusA_To(0) = '1' then
BusA <= RegBusA(7 downto 0);
else
BusA <= RegBusA(15 downto 8);
end if;
when "0110" =>
BusA <= DI_Reg;
when "1000" =>
BusA <= std_logic_vector(SP(7 downto 0));
when "1001" =>
BusA <= std_logic_vector(SP(15 downto 8));
when "1010" =>
BusA <= "00000000";
when others =>
BusB <= "--------";
end case;
end if;
end if;
end process;
---------------------------------------------------------------------------
--
-- Generate external control signals
--
---------------------------------------------------------------------------
process (RESET_n,CLK_n)
begin
if RESET_n = '0' then
RFSH_n <= '1';
elsif CLK_n'event and CLK_n = '1' then
if CEN = '1' then
if MCycle = "001" and ((TState = 2 and Wait_n = '1') or TState = 3) then
RFSH_n <= '0';
else
RFSH_n <= '1';
end if;
end if;
end if;
end process;
MC <= std_logic_vector(MCycle);
TS <= std_logic_vector(TState);
DI_Reg <= DI;
HALT_n <= not Halt_FF;
BUSAK_n <= not BusAck;
IntCycle_n <= not IntCycle;
IntE <= IntE_FF1;
IORQ <= IORQ_i;
Stop <= I_DJNZ;
-------------------------------------------------------------------------
--
-- Syncronise inputs
--
-------------------------------------------------------------------------
process (RESET_n, CLK_n)
variable OldNMI_n : std_logic;
begin
if RESET_n = '0' then
BusReq_s <= '0';
INT_s <= '0';
NMI_s <= '0';
OldNMI_n := '0';
elsif CLK_n'event and CLK_n = '1' then
if CEN = '1' then
BusReq_s <= not BUSRQ_n;
INT_s <= not INT_n;
if NMICycle = '1' then
NMI_s <= '0';
elsif NMI_n = '0' and OldNMI_n = '1' then
NMI_s <= '1';
end if;
OldNMI_n := NMI_n;
end if;
end if;
end process;
-------------------------------------------------------------------------
--
-- Main state machine
--
-------------------------------------------------------------------------
process (RESET_n, CLK_n)
begin
if RESET_n = '0' then
MCycle <= "001";
TState <= "000";
Pre_XY_F_M <= "000";
Halt_FF <= '0';
BusAck <= '0';
NMICycle <= '0';
IntCycle <= '0';
IntE_FF1 <= '0';
IntE_FF2 <= '0';
No_BTR <= '0';
Auto_Wait_t1 <= '0';
Auto_Wait_t2 <= '0';
M1_n <= '1';
elsif CLK_n'event and CLK_n = '1' then
if CEN = '1' then
Auto_Wait_t1 <= Auto_Wait;
Auto_Wait_t2 <= Auto_Wait_t1;
No_BTR <= (I_BT and (not IR(4) or not F(Flag_P))) or
(I_BC and (not IR(4) or F(Flag_Z) or not F(Flag_P))) or
(I_BTR and (not IR(4) or F(Flag_Z)));
if TState = 2 then
if SetEI = '1' then
IntE_FF1 <= '1';
IntE_FF2 <= '1';
end if;
if I_RETN = '1' then
IntE_FF1 <= IntE_FF2;
end if;
end if;
if TState = 3 then
if SetDI = '1' then
IntE_FF1 <= '0';
IntE_FF2 <= '0';
end if;
end if;
if IntCycle = '1' or NMICycle = '1' then
Halt_FF <= '0';
end if;
if MCycle = "001" and TState = 2 and Wait_n = '1' then
M1_n <= '1';
end if;
if BusReq_s = '1' and BusAck = '1' then
else
BusAck <= '0';
if TState = 2 and Wait_n = '0' then
elsif T_Res = '1' then
if Halt = '1' then
Halt_FF <= '1';
end if;
if BusReq_s = '1' then
BusAck <= '1';
else
TState <= "001";
if NextIs_XY_Fetch = '1' then
MCycle <= "110";
Pre_XY_F_M <= MCycle;
if IR = "00110110" and Mode = 0 then
Pre_XY_F_M <= "010";
end if;
elsif (MCycle = "111") or
(MCycle = "110" and Mode = 1 and ISet /= "01") then
MCycle <= std_logic_vector(unsigned(Pre_XY_F_M) + 1);
elsif (MCycle = MCycles) or
No_BTR = '1' or
(MCycle = "010" and I_DJNZ = '1' and IncDecZ = '1') then
M1_n <= '0';
MCycle <= "001";
IntCycle <= '0';
NMICycle <= '0';
if NMI_s = '1' and Prefix = "00" then
NMICycle <= '1';
IntE_FF1 <= '0';
elsif (IntE_FF1 = '1' and INT_s = '1') and Prefix = "00" and SetEI = '0' then
IntCycle <= '1';
IntE_FF1 <= '0';
IntE_FF2 <= '0';
end if;
else
MCycle <= std_logic_vector(unsigned(MCycle) + 1);
end if;
end if;
else
if Auto_Wait = '1' nand Auto_Wait_t2 = '0' then
TState <= TState + 1;
end if;
end if;
end if;
if TState = 0 then
M1_n <= '0';
end if;
end if;
end if;
end process;
process (IntCycle, NMICycle, MCycle)
begin
Auto_Wait <= '0';
if IntCycle = '1' or NMICycle = '1' then
if MCycle = "001" then
Auto_Wait <= '1';
end if;
end if;
end process;
end;