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Diffstat (limited to 'T65/T65_ALU.vhd')
| -rw-r--r-- | T65/T65_ALU.vhd | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/T65/T65_ALU.vhd b/T65/T65_ALU.vhd new file mode 100644 index 0000000..d9d25e1 --- /dev/null +++ b/T65/T65_ALU.vhd @@ -0,0 +1,260 @@ +-- ****
+-- T65(b) core. In an effort to merge and maintain bug fixes ....
+--
+--
+-- Ver 300 Bugfixes by ehenciak added
+-- MikeJ March 2005
+-- Latest version from www.fpgaarcade.com (original www.opencores.org)
+--
+-- ****
+--
+-- 6502 compatible microprocessor core
+--
+-- Version : 0245
+--
+-- 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 :
+--
+-- File history :
+--
+-- 0245 : First version
+--
+
+library IEEE;
+use IEEE.std_logic_1164.all;
+use IEEE.numeric_std.all;
+use work.T65_Pack.all;
+
+entity T65_ALU is
+ port(
+ Mode : in std_logic_vector(1 downto 0); -- "00" => 6502, "01" => 65C02, "10" => 65816
+ Op : in std_logic_vector(3 downto 0);
+ BusA : in std_logic_vector(7 downto 0);
+ BusB : in std_logic_vector(7 downto 0);
+ P_In : in std_logic_vector(7 downto 0);
+ P_Out : out std_logic_vector(7 downto 0);
+ Q : out std_logic_vector(7 downto 0)
+ );
+end T65_ALU;
+
+architecture rtl of T65_ALU is
+
+ -- AddSub variables (temporary signals)
+ signal ADC_Z : std_logic;
+ signal ADC_C : std_logic;
+ signal ADC_V : std_logic;
+ signal ADC_N : std_logic;
+ signal ADC_Q : std_logic_vector(7 downto 0);
+ signal SBC_Z : std_logic;
+ signal SBC_C : std_logic;
+ signal SBC_V : std_logic;
+ signal SBC_N : std_logic;
+ signal SBC_Q : std_logic_vector(7 downto 0);
+
+begin
+
+ process (P_In, BusA, BusB)
+ variable AL : unsigned(6 downto 0);
+ variable AH : unsigned(6 downto 0);
+ variable C : std_logic;
+ begin
+ AL := resize(unsigned(BusA(3 downto 0) & P_In(Flag_C)), 7) + resize(unsigned(BusB(3 downto 0) & "1"), 7);
+ AH := resize(unsigned(BusA(7 downto 4) & AL(5)), 7) + resize(unsigned(BusB(7 downto 4) & "1"), 7);
+
+-- pragma translate_off
+ if is_x(std_logic_vector(AL)) then AL := "0000000"; end if;
+ if is_x(std_logic_vector(AH)) then AH := "0000000"; end if;
+-- pragma translate_on
+
+ if AL(4 downto 1) = 0 and AH(4 downto 1) = 0 then
+ ADC_Z <= '1';
+ else
+ ADC_Z <= '0';
+ end if;
+
+ if AL(5 downto 1) > 9 and P_In(Flag_D) = '1' then
+ AL(6 downto 1) := AL(6 downto 1) + 6;
+ end if;
+
+ C := AL(6) or AL(5);
+ AH := resize(unsigned(BusA(7 downto 4) & C), 7) + resize(unsigned(BusB(7 downto 4) & "1"), 7);
+
+ ADC_N <= AH(4);
+ ADC_V <= (AH(4) xor BusA(7)) and not (BusA(7) xor BusB(7));
+
+-- pragma translate_off
+ if is_x(std_logic_vector(AH)) then AH := "0000000"; end if;
+-- pragma translate_on
+
+ if AH(5 downto 1) > 9 and P_In(Flag_D) = '1' then
+ AH(6 downto 1) := AH(6 downto 1) + 6;
+ end if;
+
+ ADC_C <= AH(6) or AH(5);
+
+ ADC_Q <= std_logic_vector(AH(4 downto 1) & AL(4 downto 1));
+ end process;
+
+ process (Op, P_In, BusA, BusB)
+ variable AL : unsigned(6 downto 0);
+ variable AH : unsigned(5 downto 0);
+ variable C : std_logic;
+ begin
+ C := P_In(Flag_C) or not Op(0);
+ AL := resize(unsigned(BusA(3 downto 0) & C), 7) - resize(unsigned(BusB(3 downto 0) & "1"), 6);
+ AH := resize(unsigned(BusA(7 downto 4) & "0"), 6) - resize(unsigned(BusB(7 downto 4) & AL(5)), 6);
+
+-- pragma translate_off
+ if is_x(std_logic_vector(AL)) then AL := "0000000"; end if;
+ if is_x(std_logic_vector(AH)) then AH := "000000"; end if;
+-- pragma translate_on
+
+ if AL(4 downto 1) = 0 and AH(4 downto 1) = 0 then
+ SBC_Z <= '1';
+ else
+ SBC_Z <= '0';
+ end if;
+
+ SBC_C <= not AH(5);
+ SBC_V <= (AH(4) xor BusA(7)) and (BusA(7) xor BusB(7));
+ SBC_N <= AH(4);
+
+ if P_In(Flag_D) = '1' then
+ if AL(5) = '1' then
+ AL(5 downto 1) := AL(5 downto 1) - 6;
+ end if;
+ AH := resize(unsigned(BusA(7 downto 4) & "0"), 6) - resize(unsigned(BusB(7 downto 4) & AL(6)), 6);
+ if AH(5) = '1' then
+ AH(5 downto 1) := AH(5 downto 1) - 6;
+ end if;
+ end if;
+
+ SBC_Q <= std_logic_vector(AH(4 downto 1) & AL(4 downto 1));
+ end process;
+
+ process (Op, P_In, BusA, BusB,
+ ADC_Z, ADC_C, ADC_V, ADC_N, ADC_Q,
+ SBC_Z, SBC_C, SBC_V, SBC_N, SBC_Q)
+ variable Q_t : std_logic_vector(7 downto 0);
+ begin
+ -- ORA, AND, EOR, ADC, NOP, LD, CMP, SBC
+ -- ASL, ROL, LSR, ROR, BIT, LD, DEC, INC
+ P_Out <= P_In;
+ Q_t := BusA;
+ case Op(3 downto 0) is
+ when "0000" =>
+ -- ORA
+ Q_t := BusA or BusB;
+ when "0001" =>
+ -- AND
+ Q_t := BusA and BusB;
+ when "0010" =>
+ -- EOR
+ Q_t := BusA xor BusB;
+ when "0011" =>
+ -- ADC
+ P_Out(Flag_V) <= ADC_V;
+ P_Out(Flag_C) <= ADC_C;
+ Q_t := ADC_Q;
+ when "0101" | "1101" =>
+ -- LDA
+ when "0110" =>
+ -- CMP
+ P_Out(Flag_C) <= SBC_C;
+ when "0111" =>
+ -- SBC
+ P_Out(Flag_V) <= SBC_V;
+ P_Out(Flag_C) <= SBC_C;
+ Q_t := SBC_Q;
+ when "1000" =>
+ -- ASL
+ Q_t := BusA(6 downto 0) & "0";
+ P_Out(Flag_C) <= BusA(7);
+ when "1001" =>
+ -- ROL
+ Q_t := BusA(6 downto 0) & P_In(Flag_C);
+ P_Out(Flag_C) <= BusA(7);
+ when "1010" =>
+ -- LSR
+ Q_t := "0" & BusA(7 downto 1);
+ P_Out(Flag_C) <= BusA(0);
+ when "1011" =>
+ -- ROR
+ Q_t := P_In(Flag_C) & BusA(7 downto 1);
+ P_Out(Flag_C) <= BusA(0);
+ when "1100" =>
+ -- BIT
+ P_Out(Flag_V) <= BusB(6);
+ when "1110" =>
+ -- DEC
+ Q_t := std_logic_vector(unsigned(BusA) - 1);
+ when "1111" =>
+ -- INC
+ Q_t := std_logic_vector(unsigned(BusA) + 1);
+ when others =>
+ end case;
+
+ case Op(3 downto 0) is
+ when "0011" =>
+ P_Out(Flag_N) <= ADC_N;
+ P_Out(Flag_Z) <= ADC_Z;
+ when "0110" | "0111" =>
+ P_Out(Flag_N) <= SBC_N;
+ P_Out(Flag_Z) <= SBC_Z;
+ when "0100" =>
+ when "1100" =>
+ P_Out(Flag_N) <= BusB(7);
+ if (BusA and BusB) = "00000000" then
+ P_Out(Flag_Z) <= '1';
+ else
+ P_Out(Flag_Z) <= '0';
+ end if;
+ when others =>
+ P_Out(Flag_N) <= Q_t(7);
+ if Q_t = "00000000" then
+ P_Out(Flag_Z) <= '1';
+ else
+ P_Out(Flag_Z) <= '0';
+ end if;
+ end case;
+
+ Q <= Q_t;
+ end process;
+
+end;
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