-- ****
-- T80(b) core. In an effort to merge and maintain bug fixes ....
--
--
-- Ver 300 started tidyup
-- MikeJ March 2005
-- Latest version from www.fpgaarcade.com (original www.opencores.org)
--
-- ****
--
-- Z80 compatible microprocessor core, asynchronous top level
--
-- 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
--
-- 0211 : Fixed interrupt cycle
--
-- 0235 : Updated for T80 interface change
--
-- 0238 : Updated for T80 interface change
--
-- 0240 : Updated for T80 interface change
--
-- 0242 : Updated for T80 interface change
--
-- 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 T80a 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;
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;
MREQ_n : out std_logic;
IORQ_n : out std_logic;
RD_n : out std_logic;
WR_n : 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);
D : inout std_logic_vector(7 downto 0);
D_I : in std_logic_vector(7 downto 0);
D_O : out std_logic_vector(7 downto 0)
);
end T80a;
architecture rtl of T80a is
signal CEN : std_logic;
signal Reset_s : std_logic;
signal IntCycle_n : std_logic;
signal IORQ : std_logic;
signal NoRead : std_logic;
signal Write : std_logic;
signal MREQ : std_logic;
signal MReq_Inhibit : std_logic;
signal Req_Inhibit : std_logic;
signal RD : std_logic;
signal MREQ_n_i : std_logic;
signal IORQ_n_i : std_logic;
signal RD_n_i : std_logic;
signal WR_n_i : std_logic;
signal RFSH_n_i : std_logic;
signal BUSAK_n_i : std_logic;
signal A_i : std_logic_vector(15 downto 0);
signal DO : std_logic_vector(7 downto 0);
signal DI_Reg : std_logic_vector (7 downto 0); -- Input synchroniser
signal Wait_s : std_logic;
signal MCycle : std_logic_vector(2 downto 0);
signal TState : std_logic_vector(2 downto 0);
begin
CEN <= '1';
BUSAK_n <= BUSAK_n_i;
MREQ_n_i <= not MREQ or (Req_Inhibit and MReq_Inhibit);
RD_n_i <= not RD or Req_Inhibit;
MREQ_n <= MREQ_n_i when BUSAK_n_i = '1' else 'Z';
IORQ_n <= IORQ_n_i when BUSAK_n_i = '1' else 'Z';
RD_n <= RD_n_i when BUSAK_n_i = '1' else 'Z';
WR_n <= WR_n_i when BUSAK_n_i = '1' else 'Z';
RFSH_n <= RFSH_n_i when BUSAK_n_i = '1' else 'Z';
A <= A_i when BUSAK_n_i = '1' else (others => 'Z');
D <= DO when Write = '1' and BUSAK_n_i = '1' else (others => 'Z');
D_O <= DO when Write = '1' and BUSAK_n_i = '1' else (others => 'Z');
process (RESET_n, CLK_n)
begin
if RESET_n = '0' then
Reset_s <= '0';
elsif CLK_n'event and CLK_n = '1' then
Reset_s <= '1';
end if;
end process;
u0 : T80
generic map(
Mode => Mode,
IOWait => 1)
port map(
CEN => CEN,
M1_n => M1_n,
IORQ => IORQ,
NoRead => NoRead,
Write => Write,
RFSH_n => RFSH_n_i,
HALT_n => HALT_n,
WAIT_n => Wait_s,
INT_n => INT_n,
NMI_n => NMI_n,
RESET_n => Reset_s,
BUSRQ_n => BUSRQ_n,
BUSAK_n => BUSAK_n_i,
CLK_n => CLK_n,
A => A_i,
DInst => D_I, -- D -> D_I
DI => DI_Reg,
DO => DO,
MC => MCycle,
TS => TState,
IntCycle_n => IntCycle_n);
process (CLK_n)
begin
if CLK_n'event and CLK_n = '0' then
Wait_s <= WAIT_n;
if TState = "011" and BUSAK_n_i = '1' then
DI_Reg <= to_x01(D_I); -- D -> D_I
end if;
end if;
end process;
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
WR_n_i <= '1';
elsif CLK_n'event and CLK_n = '1' then
WR_n_i <= '1';
if TState = "001" then -- To short for IO writes !!!!!!!!!!!!!!!!!!!
WR_n_i <= not Write;
end if;
end if;
end process;
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
Req_Inhibit <= '0';
elsif CLK_n'event and CLK_n = '1' then
if MCycle = "001" and TState = "010" then
Req_Inhibit <= '1';
else
Req_Inhibit <= '0';
end if;
end if;
end process;
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
MReq_Inhibit <= '0';
elsif CLK_n'event and CLK_n = '0' then
if MCycle = "001" and TState = "010" then
MReq_Inhibit <= '1';
else
MReq_Inhibit <= '0';
end if;
end if;
end process;
process(Reset_s,CLK_n)
begin
if Reset_s = '0' then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '0';
elsif CLK_n'event and CLK_n = '0' then
if MCycle = "001" then
if TState = "001" then
RD <= IntCycle_n;
MREQ <= IntCycle_n;
IORQ_n_i <= IntCycle_n;
end if;
if TState = "011" then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '1';
end if;
if TState = "100" then
MREQ <= '0';
end if;
else
if TState = "001" and NoRead = '0' then
RD <= not Write;
IORQ_n_i <= not IORQ;
MREQ <= not IORQ;
end if;
if TState = "011" then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '0';
end if;
end if;
end if;
end process;
end;