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6bb256b7ab
AtomBusMon/src/T6502/T65.vhd
David Banks 6bb256b7ab Added Blank design and T65-based 6502 design 
Change-Id: I3b426484bfad6843d6346064e0eb22b9bf3a9c82
2015-06-14 17:57:26 +01:00

565 lines
20 KiB
VHDL
Executable File
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-- ****
-- T65(b) core. In an effort to merge and maintain bug fixes ....
--
--
-- Ver 301 more merging
-- Ver 300 Bugfixes by ehenciak added, started tidyup *bust*
-- MikeJ March 2005
-- Latest version from www.fpgaarcade.com (original www.opencores.org)
--
-- ****
--
-- 65xx compatible microprocessor core
--
-- Version : 0246
--
-- Copyright (c) 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/t65/
--
-- Limitations :
--
-- 65C02 and 65C816 modes are incomplete
-- Undocumented instructions are not supported
-- Some interface signals behaves incorrect
--
-- File history :
--
-- 0246 : First release
--
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use work.T65_Pack.all;
-- ehenciak 2-23-2005 : Added the enable signal so that one doesn't have to use
-- the ready signal to limit the CPU.
entity T65 is
port(
Mode : in std_logic_vector(1 downto 0); -- "00" => 6502, "01" => 65C02, "10" => 65C816
Res_n : in std_logic;
Enable : in std_logic;
Clk : in std_logic;
Rdy : in std_logic;
Abort_n : in std_logic;
IRQ_n : in std_logic;
NMI_n : in std_logic;
SO_n : in std_logic;
R_W_n : out std_logic;
Sync : out std_logic;
EF : out std_logic;
MF : out std_logic;
XF : out std_logic;
ML_n : out std_logic;
VP_n : out std_logic;
VDA : out std_logic;
VPA : out std_logic;
A : out std_logic_vector(23 downto 0);
DI : in std_logic_vector(7 downto 0);
DO : out std_logic_vector(7 downto 0)
);
end T65;
architecture rtl of T65 is
-- Registers
signal ABC, X, Y, D : std_logic_vector(15 downto 0);
signal P, AD, DL : std_logic_vector(7 downto 0) := x"00";
signal BAH : std_logic_vector(7 downto 0);
signal BAL : std_logic_vector(8 downto 0);
signal PBR : std_logic_vector(7 downto 0);
signal DBR : std_logic_vector(7 downto 0);
signal PC : unsigned(15 downto 0);
signal S : unsigned(15 downto 0);
signal EF_i : std_logic;
signal MF_i : std_logic;
signal XF_i : std_logic;
signal IR : std_logic_vector(7 downto 0);
signal MCycle : std_logic_vector(2 downto 0);
signal Mode_r : std_logic_vector(1 downto 0);
signal ALU_Op_r : std_logic_vector(3 downto 0);
signal Write_Data_r : std_logic_vector(2 downto 0);
signal Set_Addr_To_r : std_logic_vector(1 downto 0);
signal PCAdder : unsigned(8 downto 0);
signal RstCycle : std_logic;
signal IRQCycle : std_logic;
signal NMICycle : std_logic;
signal B_o : std_logic;
signal SO_n_o : std_logic;
signal IRQ_n_o : std_logic;
signal NMI_n_o : std_logic;
signal NMIAct : std_logic;
signal Break : std_logic;
-- ALU signals
signal BusA : std_logic_vector(7 downto 0);
signal BusA_r : std_logic_vector(7 downto 0);
signal BusB : std_logic_vector(7 downto 0);
signal ALU_Q : std_logic_vector(7 downto 0);
signal P_Out : std_logic_vector(7 downto 0);
-- Micro code outputs
signal LCycle : std_logic_vector(2 downto 0);
signal ALU_Op : std_logic_vector(3 downto 0);
signal Set_BusA_To : std_logic_vector(2 downto 0);
signal Set_Addr_To : std_logic_vector(1 downto 0);
signal Write_Data : std_logic_vector(2 downto 0);
signal Jump : std_logic_vector(1 downto 0);
signal BAAdd : std_logic_vector(1 downto 0);
signal BreakAtNA : std_logic;
signal ADAdd : std_logic;
signal AddY : std_logic;
signal PCAdd : std_logic;
signal Inc_S : std_logic;
signal Dec_S : std_logic;
signal LDA : std_logic;
signal LDP : std_logic;
signal LDX : std_logic;
signal LDY : std_logic;
signal LDS : std_logic;
signal LDDI : std_logic;
signal LDALU : std_logic;
signal LDAD : std_logic;
signal LDBAL : std_logic;
signal LDBAH : std_logic;
signal SaveP : std_logic;
signal Write : std_logic;
signal really_rdy : std_logic;
signal R_W_n_i : std_logic;
begin
-- ehenciak : gate Rdy with read/write to make an "OK, it's
-- really OK to stop the processor now if Rdy is
-- deasserted" signal
really_rdy <= Rdy or not(R_W_n_i);
-- ehenciak : Drive R_W_n_i off chip.
R_W_n <= R_W_n_i;
Sync <= '1' when MCycle = "000" else '0';
EF <= EF_i;
MF <= MF_i;
XF <= XF_i;
ML_n <= '0' when IR(7 downto 6) /= "10" and IR(2 downto 1) = "11" and MCycle(2 downto 1) /= "00" else '1';
VP_n <= '0' when IRQCycle = '1' and (MCycle = "101" or MCycle = "110") else '1';
VDA <= '1' when Set_Addr_To_r /= "00" else '0'; -- Incorrect !!!!!!!!!!!!
VPA <= '1' when Jump(1) = '0' else '0'; -- Incorrect !!!!!!!!!!!!
mcode : T65_MCode
port map(
Mode => Mode_r,
IR => IR,
MCycle => MCycle,
P => P,
LCycle => LCycle,
ALU_Op => ALU_Op,
Set_BusA_To => Set_BusA_To,
Set_Addr_To => Set_Addr_To,
Write_Data => Write_Data,
Jump => Jump,
BAAdd => BAAdd,
BreakAtNA => BreakAtNA,
ADAdd => ADAdd,
AddY => AddY,
PCAdd => PCAdd,
Inc_S => Inc_S,
Dec_S => Dec_S,
LDA => LDA,
LDP => LDP,
LDX => LDX,
LDY => LDY,
LDS => LDS,
LDDI => LDDI,
LDALU => LDALU,
LDAD => LDAD,
LDBAL => LDBAL,
LDBAH => LDBAH,
SaveP => SaveP,
Write => Write
);
alu : T65_ALU
port map(
Mode => Mode_r,
Op => ALU_Op_r,
BusA => BusA_r,
BusB => BusB,
P_In => P,
P_Out => P_Out,
Q => ALU_Q
);
process (Res_n, Clk)
begin
if Res_n = '0' then
PC <= (others => '0'); -- Program Counter
IR <= "00000000";
S <= (others => '0'); -- Dummy !!!!!!!!!!!!!!!!!!!!!
D <= (others => '0');
PBR <= (others => '0');
DBR <= (others => '0');
Mode_r <= (others => '0');
ALU_Op_r <= "1100";
Write_Data_r <= "000";
Set_Addr_To_r <= "00";
R_W_n_i <= '1';
EF_i <= '1';
MF_i <= '1';
XF_i <= '1';
elsif Clk'event and Clk = '1' then
if (Enable = '1') then
if (really_rdy = '1') then
R_W_n_i <= not Write or RstCycle;
D <= (others => '1'); -- Dummy
PBR <= (others => '1'); -- Dummy
DBR <= (others => '1'); -- Dummy
EF_i <= '0'; -- Dummy
MF_i <= '0'; -- Dummy
XF_i <= '0'; -- Dummy
if MCycle = "000" then
Mode_r <= Mode;
if IRQCycle = '0' and NMICycle = '0' then
PC <= PC + 1;
end if;
if IRQCycle = '1' or NMICycle = '1' then
IR <= "00000000";
else
IR <= DI;
end if;
end if;
ALU_Op_r <= ALU_Op;
Write_Data_r <= Write_Data;
if Break = '1' then
Set_Addr_To_r <= "00";
else
Set_Addr_To_r <= Set_Addr_To;
end if;
if Inc_S = '1' then
S <= S + 1;
end if;
if Dec_S = '1' and RstCycle = '0' then
S <= S - 1;
end if;
if LDS = '1' then
S(7 downto 0) <= unsigned(ALU_Q);
end if;
if IR = "00000000" and MCycle = "001" and IRQCycle = '0' and NMICycle = '0' then
PC <= PC + 1;
end if;
--
-- jump control logic
--
case Jump is
when "01" =>
PC <= PC + 1;
when "10" =>
PC <= unsigned(DI & DL);
when "11" =>
if PCAdder(8) = '1' then
if DL(7) = '0' then
PC(15 downto 8) <= PC(15 downto 8) + 1;
else
PC(15 downto 8) <= PC(15 downto 8) - 1;
end if;
end if;
PC(7 downto 0) <= PCAdder(7 downto 0);
when others => null;
end case;
end if;
end if;
end if;
end process;
PCAdder <= resize(PC(7 downto 0), 9) + resize(unsigned(DL(7) & DL), 9) when PCAdd = '1'
else "0" & PC(7 downto 0);
process (Clk)
begin
if Clk'event and Clk = '1' then
if (Enable = '1') then
if (really_rdy = '1') then
if MCycle = "000" then
if LDA = '1' then
ABC(7 downto 0) <= ALU_Q;
end if;
if LDX = '1' then
X(7 downto 0) <= ALU_Q;
end if;
if LDY = '1' then
Y(7 downto 0) <= ALU_Q;
end if;
if (LDA or LDX or LDY) = '1' then
P <= P_Out;
end if;
end if;
if SaveP = '1' then
P <= P_Out;
end if;
if LDP = '1' then
P <= ALU_Q;
end if;
if IR(4 downto 0) = "11000" then
case IR(7 downto 5) is
when "000" =>
P(Flag_C) <= '0';
when "001" =>
P(Flag_C) <= '1';
when "010" =>
P(Flag_I) <= '0';
when "011" =>
P(Flag_I) <= '1';
when "101" =>
P(Flag_V) <= '0';
when "110" =>
P(Flag_D) <= '0';
when "111" =>
P(Flag_D) <= '1';
when others =>
end case;
end if;
--if IR = "00000000" and MCycle = "011" and RstCycle = '0' and NMICycle = '0' and IRQCycle = '0' then
-- P(Flag_B) <= '1';
--end if;
--if IR = "00000000" and MCycle = "100" and RstCycle = '0' and (NMICycle = '1' or IRQCycle = '1') then
-- P(Flag_I) <= '1';
-- P(Flag_B) <= B_o;
--end if;
-- B=1 always on the 6502
P(Flag_B) <= '1';
if IR = "00000000" and RstCycle = '0' and (NMICycle = '1' or IRQCycle = '1') then
if MCycle = "011" then
-- B=0 in *copy* of P pushed onto the stack
P(Flag_B) <= '0';
elsif MCycle = "100" then
P(Flag_I) <= '1';
end if;
end if;
if SO_n_o = '1' and SO_n = '0' then
P(Flag_V) <= '1';
end if;
if RstCycle = '1' and Mode_r /= "00" then
P(Flag_1) <= '1';
P(Flag_D) <= '0';
P(Flag_I) <= '1';
end if;
P(Flag_1) <= '1';
B_o <= P(Flag_B);
SO_n_o <= SO_n;
IRQ_n_o <= IRQ_n;
NMI_n_o <= NMI_n;
end if;
end if;
end if;
end process;
---------------------------------------------------------------------------
--
-- Buses
--
---------------------------------------------------------------------------
process (Res_n, Clk)
begin
if Res_n = '0' then
BusA_r <= (others => '0');
BusB <= (others => '0');
AD <= (others => '0');
BAL <= (others => '0');
BAH <= (others => '0');
DL <= (others => '0');
elsif Clk'event and Clk = '1' then
if (Enable = '1') then
if (Rdy = '1') then
BusA_r <= BusA;
BusB <= DI;
case BAAdd is
when "01" =>
-- BA Inc
AD <= std_logic_vector(unsigned(AD) + 1);
BAL <= std_logic_vector(unsigned(BAL) + 1);
when "10" =>
-- BA Add
BAL <= std_logic_vector(resize(unsigned(BAL(7 downto 0)), 9) + resize(unsigned(BusA), 9));
when "11" =>
-- BA Adj
if BAL(8) = '1' then
BAH <= std_logic_vector(unsigned(BAH) + 1);
end if;
when others =>
end case;
-- ehenciak : modified to use Y register as well (bugfix)
if ADAdd = '1' then
if (AddY = '1') then
AD <= std_logic_vector(unsigned(AD) + unsigned(Y(7 downto 0)));
else
AD <= std_logic_vector(unsigned(AD) + unsigned(X(7 downto 0)));
end if;
end if;
if IR = "00000000" then
BAL <= (others => '1');
BAH <= (others => '1');
if RstCycle = '1' then
BAL(2 downto 0) <= "100";
elsif NMICycle = '1' then
BAL(2 downto 0) <= "010";
else
BAL(2 downto 0) <= "110";
end if;
if Set_addr_To_r = "11" then
BAL(0) <= '1';
end if;
end if;
if LDDI = '1' then
DL <= DI;
end if;
if LDALU = '1' then
DL <= ALU_Q;
end if;
if LDAD = '1' then
AD <= DI;
end if;
if LDBAL = '1' then
BAL(7 downto 0) <= DI;
end if;
if LDBAH = '1' then
BAH <= DI;
end if;
end if;
end if;
end if;
end process;
Break <= (BreakAtNA and not BAL(8)) or (PCAdd and not PCAdder(8));
with Set_BusA_To select
BusA <= DI when "000",
ABC(7 downto 0) when "001",
X(7 downto 0) when "010",
Y(7 downto 0) when "011",
std_logic_vector(S(7 downto 0)) when "100",
P when "101",
(others => '-') when others;
with Set_Addr_To_r select
A <= "0000000000000001" & std_logic_vector(S(7 downto 0)) when "01",
DBR & "00000000" & AD when "10",
"00000000" & BAH & BAL(7 downto 0) when "11",
PBR & std_logic_vector(PC(15 downto 8)) & std_logic_vector(PCAdder(7 downto 0)) when others;
with Write_Data_r select
DO <= DL when "000",
ABC(7 downto 0) when "001",
X(7 downto 0) when "010",
Y(7 downto 0) when "011",
std_logic_vector(S(7 downto 0)) when "100",
P when "101",
std_logic_vector(PC(7 downto 0)) when "110",
std_logic_vector(PC(15 downto 8)) when others;
-------------------------------------------------------------------------
--
-- Main state machine
--
-------------------------------------------------------------------------
process (Res_n, Clk)
begin
if Res_n = '0' then
MCycle <= "001";
RstCycle <= '1';
IRQCycle <= '0';
NMICycle <= '0';
NMIAct <= '0';
elsif Clk'event and Clk = '1' then
if (Enable = '1') then
if (really_rdy = '1') then
if MCycle = LCycle or Break = '1' then
MCycle <= "000";
RstCycle <= '0';
IRQCycle <= '0';
NMICycle <= '0';
if NMIAct = '1' then
NMICycle <= '1';
elsif IRQ_n_o = '0' and P(Flag_I) = '0' then
IRQCycle <= '1';
end if;
else
MCycle <= std_logic_vector(unsigned(MCycle) + 1);
end if;
if NMICycle = '1' then
NMIAct <= '0';
end if;
if NMI_n_o = '1' and NMI_n = '0' then
NMIAct <= '1';
end if;
end if;
end if;
end if;
end process;
end;
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