-- ****
-- T80(b) core. In an effort to merge and maintain bug fixes ....
--
--
-- Ver 301 parity flag is just parity for 8080, also overflow for Z80, by Sean Riddle
-- Ver 300 started tidyup
-- 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 :
--
-- 0214 : Fixed mostly flags, only the block instructions now fail the zex regression test
--
-- 0238 : Fixed zero flag for 16 bit SBC and ADC
--
-- 0240 : Added GB operations
--
-- 0242 : Cleanup
--
-- 0247 : Cleanup
--
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
entity T80_ALU is
generic(
Mode : integer := 0;
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(
Arith16 : in std_logic;
Z16 : in std_logic;
ALU_Op : in std_logic_vector(3 downto 0);
IR : in std_logic_vector(5 downto 0);
ISet : in std_logic_vector(1 downto 0);
BusA : in std_logic_vector(7 downto 0);
BusB : in std_logic_vector(7 downto 0);
F_In : in std_logic_vector(7 downto 0);
Q : out std_logic_vector(7 downto 0);
F_Out : out std_logic_vector(7 downto 0)
);
end T80_ALU;
architecture rtl of T80_ALU is
procedure AddSub(A : std_logic_vector;
B : std_logic_vector;
Sub : std_logic;
Carry_In : std_logic;
signal Res : out std_logic_vector;
signal Carry : out std_logic) is
variable B_i : unsigned(A'length - 1 downto 0);
variable Res_i : unsigned(A'length + 1 downto 0);
begin
if Sub = '1' then
B_i := not unsigned(B);
else
B_i := unsigned(B);
end if;
Res_i := unsigned("0" & A & Carry_In) + unsigned("0" & B_i & "1");
Carry <= Res_i(A'length + 1);
Res <= std_logic_vector(Res_i(A'length downto 1));
end;
-- AddSub variables (temporary signals)
signal UseCarry : std_logic;
signal Carry7_v : std_logic;
signal Overflow_v : std_logic;
signal HalfCarry_v : std_logic;
signal Carry_v : std_logic;
signal Q_v : std_logic_vector(7 downto 0);
signal BitMask : std_logic_vector(7 downto 0);
begin
with IR(5 downto 3) select BitMask <= "00000001" when "000",
"00000010" when "001",
"00000100" when "010",
"00001000" when "011",
"00010000" when "100",
"00100000" when "101",
"01000000" when "110",
"10000000" when others;
UseCarry <= not ALU_Op(2) and ALU_Op(0);
AddSub(BusA(3 downto 0), BusB(3 downto 0), ALU_Op(1), ALU_Op(1) xor (UseCarry and F_In(Flag_C)), Q_v(3 downto 0), HalfCarry_v);
AddSub(BusA(6 downto 4), BusB(6 downto 4), ALU_Op(1), HalfCarry_v, Q_v(6 downto 4), Carry7_v);
AddSub(BusA(7 downto 7), BusB(7 downto 7), ALU_Op(1), Carry7_v, Q_v(7 downto 7), Carry_v);
-- bug fix - parity flag is just parity for 8080, also overflow for Z80
process (Carry_v, Carry7_v, Q_v)
begin
if(Mode=2) then
OverFlow_v <= not (Q_v(0) xor Q_v(1) xor Q_v(2) xor Q_v(3) xor
Q_v(4) xor Q_v(5) xor Q_v(6) xor Q_v(7)); else
OverFlow_v <= Carry_v xor Carry7_v;
end if;
end process;
process (Arith16, ALU_OP, F_In, BusA, BusB, IR, Q_v, Carry_v, HalfCarry_v, OverFlow_v, BitMask, ISet, Z16)
variable Q_t : std_logic_vector(7 downto 0);
variable DAA_Q : unsigned(8 downto 0);
begin
Q_t := "--------";
F_Out <= F_In;
DAA_Q := "---------";
case ALU_Op is
when "0000" | "0001" | "0010" | "0011" | "0100" | "0101" | "0110" | "0111" =>
F_Out(Flag_N) <= '0';
F_Out(Flag_C) <= '0';
case ALU_OP(2 downto 0) is
when "000" | "001" => -- ADD, ADC
Q_t := Q_v;
F_Out(Flag_C) <= Carry_v;
F_Out(Flag_H) <= HalfCarry_v;
F_Out(Flag_P) <= OverFlow_v;
when "010" | "011" | "111" => -- SUB, SBC, CP
Q_t := Q_v;
F_Out(Flag_N) <= '1';
F_Out(Flag_C) <= not Carry_v;
F_Out(Flag_H) <= not HalfCarry_v;
F_Out(Flag_P) <= OverFlow_v;
when "100" => -- AND
Q_t(7 downto 0) := BusA and BusB;
F_Out(Flag_H) <= '1';
when "101" => -- XOR
Q_t(7 downto 0) := BusA xor BusB;
F_Out(Flag_H) <= '0';
when others => -- OR "110"
Q_t(7 downto 0) := BusA or BusB;
F_Out(Flag_H) <= '0';
end case;
if ALU_Op(2 downto 0) = "111" then -- CP
F_Out(Flag_X) <= BusB(3);
F_Out(Flag_Y) <= BusB(5);
else
F_Out(Flag_X) <= Q_t(3);
F_Out(Flag_Y) <= Q_t(5);
end if;
if Q_t(7 downto 0) = "00000000" then
F_Out(Flag_Z) <= '1';
if Z16 = '1' then
F_Out(Flag_Z) <= F_In(Flag_Z); -- 16 bit ADC,SBC
end if;
else
F_Out(Flag_Z) <= '0';
end if;
F_Out(Flag_S) <= Q_t(7);
case ALU_Op(2 downto 0) is
when "000" | "001" | "010" | "011" | "111" => -- ADD, ADC, SUB, SBC, CP
when others =>
F_Out(Flag_P) <= not (Q_t(0) xor Q_t(1) xor Q_t(2) xor Q_t(3) xor
Q_t(4) xor Q_t(5) xor Q_t(6) xor Q_t(7));
end case;
if Arith16 = '1' then
F_Out(Flag_S) <= F_In(Flag_S);
F_Out(Flag_Z) <= F_In(Flag_Z);
F_Out(Flag_P) <= F_In(Flag_P);
end if;
when "1100" =>
-- DAA
F_Out(Flag_H) <= F_In(Flag_H);
F_Out(Flag_C) <= F_In(Flag_C);
DAA_Q(7 downto 0) := unsigned(BusA);
DAA_Q(8) := '0';
if F_In(Flag_N) = '0' then
-- After addition
-- Alow > 9 or H = 1
if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
if (DAA_Q(3 downto 0) > 9) then
F_Out(Flag_H) <= '1';
else
F_Out(Flag_H) <= '0';
end if;
DAA_Q := DAA_Q + 6;
end if;
-- new Ahigh > 9 or C = 1
if DAA_Q(8 downto 4) > 9 or F_In(Flag_C) = '1' then
DAA_Q := DAA_Q + 96; -- 0x60
end if;
else
-- After subtraction
if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
if DAA_Q(3 downto 0) > 5 then
F_Out(Flag_H) <= '0';
end if;
DAA_Q(7 downto 0) := DAA_Q(7 downto 0) - 6;
end if;
if unsigned(BusA) > 153 or F_In(Flag_C) = '1' then
DAA_Q := DAA_Q - 352; -- 0x160
end if;
end if;
F_Out(Flag_X) <= DAA_Q(3);
F_Out(Flag_Y) <= DAA_Q(5);
F_Out(Flag_C) <= F_In(Flag_C) or DAA_Q(8);
Q_t := std_logic_vector(DAA_Q(7 downto 0));
if DAA_Q(7 downto 0) = "00000000" then
F_Out(Flag_Z) <= '1';
else
F_Out(Flag_Z) <= '0';
end if;
F_Out(Flag_S) <= DAA_Q(7);
F_Out(Flag_P) <= not (DAA_Q(0) xor DAA_Q(1) xor DAA_Q(2) xor DAA_Q(3) xor
DAA_Q(4) xor DAA_Q(5) xor DAA_Q(6) xor DAA_Q(7));
when "1101" | "1110" =>
-- RLD, RRD
Q_t(7 downto 4) := BusA(7 downto 4);
if ALU_Op(0) = '1' then
Q_t(3 downto 0) := BusB(7 downto 4);
else
Q_t(3 downto 0) := BusB(3 downto 0);
end if;
F_Out(Flag_H) <= '0';
F_Out(Flag_N) <= '0';
F_Out(Flag_X) <= Q_t(3);
F_Out(Flag_Y) <= Q_t(5);
if Q_t(7 downto 0) = "00000000" then
F_Out(Flag_Z) <= '1';
else
F_Out(Flag_Z) <= '0';
end if;
F_Out(Flag_S) <= Q_t(7);
F_Out(Flag_P) <= not (Q_t(0) xor Q_t(1) xor Q_t(2) xor Q_t(3) xor
Q_t(4) xor Q_t(5) xor Q_t(6) xor Q_t(7));
when "1001" =>
-- BIT
Q_t(7 downto 0) := BusB and BitMask;
F_Out(Flag_S) <= Q_t(7);
if Q_t(7 downto 0) = "00000000" then
F_Out(Flag_Z) <= '1';
F_Out(Flag_P) <= '1';
else
F_Out(Flag_Z) <= '0';
F_Out(Flag_P) <= '0';
end if;
F_Out(Flag_H) <= '1';
F_Out(Flag_N) <= '0';
F_Out(Flag_X) <= '0';
F_Out(Flag_Y) <= '0';
if IR(2 downto 0) /= "110" then
F_Out(Flag_X) <= BusB(3);
F_Out(Flag_Y) <= BusB(5);
end if;
when "1010" =>
-- SET
Q_t(7 downto 0) := BusB or BitMask;
when "1011" =>
-- RES
Q_t(7 downto 0) := BusB and not BitMask;
when "1000" =>
-- ROT
case IR(5 downto 3) is
when "000" => -- RLC
Q_t(7 downto 1) := BusA(6 downto 0);
Q_t(0) := BusA(7);
F_Out(Flag_C) <= BusA(7);
when "010" => -- RL
Q_t(7 downto 1) := BusA(6 downto 0);
Q_t(0) := F_In(Flag_C);
F_Out(Flag_C) <= BusA(7);
when "001" => -- RRC
Q_t(6 downto 0) := BusA(7 downto 1);
Q_t(7) := BusA(0);
F_Out(Flag_C) <= BusA(0);
when "011" => -- RR
Q_t(6 downto 0) := BusA(7 downto 1);
Q_t(7) := F_In(Flag_C);
F_Out(Flag_C) <= BusA(0);
when "100" => -- SLA
Q_t(7 downto 1) := BusA(6 downto 0);
Q_t(0) := '0';
F_Out(Flag_C) <= BusA(7);
when "110" => -- SLL (Undocumented) / SWAP
if Mode = 3 then
Q_t(7 downto 4) := BusA(3 downto 0);
Q_t(3 downto 0) := BusA(7 downto 4);
F_Out(Flag_C) <= '0';
else
Q_t(7 downto 1) := BusA(6 downto 0);
Q_t(0) := '1';
F_Out(Flag_C) <= BusA(7);
end if;
when "101" => -- SRA
Q_t(6 downto 0) := BusA(7 downto 1);
Q_t(7) := BusA(7);
F_Out(Flag_C) <= BusA(0);
when others => -- SRL
Q_t(6 downto 0) := BusA(7 downto 1);
Q_t(7) := '0';
F_Out(Flag_C) <= BusA(0);
end case;
F_Out(Flag_H) <= '0';
F_Out(Flag_N) <= '0';
F_Out(Flag_X) <= Q_t(3);
F_Out(Flag_Y) <= Q_t(5);
F_Out(Flag_S) <= Q_t(7);
if Q_t(7 downto 0) = "00000000" then
F_Out(Flag_Z) <= '1';
else
F_Out(Flag_Z) <= '0';
end if;
F_Out(Flag_P) <= not (Q_t(0) xor Q_t(1) xor Q_t(2) xor Q_t(3) xor
Q_t(4) xor Q_t(5) xor Q_t(6) xor Q_t(7));
if ISet = "00" then
F_Out(Flag_P) <= F_In(Flag_P);
F_Out(Flag_S) <= F_In(Flag_S);
F_Out(Flag_Z) <= F_In(Flag_Z);
end if;
when others =>
null;
end case;
Q <= Q_t;
end process;
end;