--===========================================================================--
-- --
-- pia_timer.vhd - Synthesizable Parallel Interface Adapter with Timer --
-- --
--===========================================================================--
--
-- File name : pia_timer.vhd
--
-- Entity name : pia_timer
--
-- Purpose : Implements 2 x 8 bit parallel I/O ports
-- with 8 bit presetable counter.
-- Port A Data = output connected to presettable counter input
-- Port B Data = input connected to counter output
-- Used with Digilent Spartan 3E starter board
-- to implement a single step trace function.
--
-- Dependencies : ieee.std_logic_1164
-- ieee.std_logic_unsigned
-- unisim.vcomponents
--
-- Author : John E. Kent
--
-- Email : dilbert57 at the domain opencores.org
--
-- Web : http://opencores.org/project,system09
--
-- Description : Register Memory Map
--
-- Base + $00 - Port A Data & Direction register
-- Base + $01 - Port A Control register
-- Base + $02 - Port B Data & Direction Direction Register
-- Base + $03 - Port B Control Register
--
-- Copyright (C) 2004 - 2010 John Kent
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program. If not, see <http://www.gnu.org/licenses/>.
--
--===========================================================================--
-- --
-- Revision History --
-- --
--===========================================================================--
--
-- Version Author Date Description
-- 0.0 John Kent 1st May 2004 Initial version developed from ioport.vhd
--
-- 1.0 John Kent 22nd April 2006 Removed I/O ports and hard wired a binary
-- down counter. Port A is the preset output.
-- Port B is the timer count input.
-- CA1 & CB1 are interrupt inputs
-- CA2 is the counter load (active low)
-- CB2 is the counter reset (active high)
-- It may be necessary to offset the counter
-- to compensate for differences in cpu cycle
-- times between FPGA and real 6809 systems.
--
-- 1.1 John Kent 24th May 2006 Modified counter to subtract one from preset
-- so FPGA version of the CMC_BUG monitor is
-- compatible with the reference design.
--
-- 1.2 John Kent 30th May 2010 Revised header and added updated GPL
--
--===========================================================================----
--
-- Memory Map
--
-- IO + $00 - Port A Data & Direction register
-- IO + $01 - Port A Control register
-- IO + $02 - Port B Data & Direction Direction Register
-- IO + $03 - Port B Control Register
--
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
library unisim;
use unisim.vcomponents.all;
--* @brief Synthesizable Parallel Interface Adapter with Timer
--*
--* @author John E. Kent
--* @version 1.2 from 30th May 2010
entity pia_timer is
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector(1 downto 0);
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0);
irqa : out std_logic;
irqb : out std_logic
);
end;
--* Implements 2 x 8 bit parallel I/O ports
--* with 8 bit presetable counter.
--*
--* Port A Data = output connected to presettable counter input
--*
--* Port B Data = input connected to counter output
--*
--* Used with Digilent Spartan 3E starter board
--* to implement a single step trace function.
--*
--* @author John E. Kent
--* @version 1.2 from 30th May 2010
architecture pia_arch of pia_timer is
signal pa : std_logic_vector(7 downto 0);
signal porta_ddr : std_logic_vector(7 downto 0);
signal porta_data : std_logic_vector(7 downto 0);
signal porta_ctrl : std_logic_vector(5 downto 0);
signal porta_read : std_logic;
signal pb : std_logic_vector(7 downto 0);
signal portb_ddr : std_logic_vector(7 downto 0);
signal portb_data : std_logic_vector(7 downto 0);
signal portb_ctrl : std_logic_vector(5 downto 0);
signal portb_read : std_logic;
signal portb_write : std_logic;
signal ca1 : std_logic;
signal ca1_del : std_logic;
signal ca1_rise : std_logic;
signal ca1_fall : std_logic;
signal ca1_edge : std_logic;
signal irqa1 : std_logic := '0';
signal ca2 : std_logic;
signal ca2_del : std_logic;
signal ca2_rise : std_logic;
signal ca2_fall : std_logic;
signal ca2_edge : std_logic;
signal irqa2 : std_logic := '0';
signal ca2_out : std_logic;
signal cb1 : std_logic;
signal cb1_del : std_logic;
signal cb1_rise : std_logic;
signal cb1_fall : std_logic;
signal cb1_edge : std_logic;
signal irqb1 : std_logic := '0';
signal cb2 : std_logic;
signal cb2_del : std_logic;
signal cb2_rise : std_logic;
signal cb2_fall : std_logic;
signal cb2_edge : std_logic;
signal irqb2 : std_logic := '0';
signal cb2_out : std_logic;
-- 74193 down counter
signal timer : std_logic_vector(7 downto 0);
begin
--* read I/O port
--*
pia_read : process( addr, cs,
irqa1, irqa2, irqb1, irqb2,
porta_ddr, portb_ddr,
porta_data, portb_data,
porta_ctrl, portb_ctrl,
pa, pb )
variable count : integer;
begin
data_out <= "00000000";
porta_read <= '0';
portb_read <= '0';
case addr is
when "00" =>
for count in 0 to 7 loop
if porta_ctrl(2) = '0' then
data_out(count) <= porta_ddr(count);
porta_read <= '0';
else
if porta_ddr(count) = '1' then
data_out(count) <= porta_data(count);
else
data_out(count) <= pa(count);
end if;
porta_read <= cs;
end if;
end loop;
portb_read <= '0';
when "01" =>
data_out <= irqa1 & irqa2 & porta_ctrl;
porta_read <= '0';
portb_read <= '0';
when "10" =>
for count in 0 to 7 loop
if portb_ctrl(2) = '0' then
data_out(count) <= portb_ddr(count);
portb_read <= '0';
else
if portb_ddr(count) = '1' then
data_out(count) <= portb_data(count);
else
data_out(count) <= pb(count);
end if;
portb_read <= cs;
end if;
end loop;
porta_read <= '0';
when "11" =>
data_out <= irqb1 & irqb2 & portb_ctrl;
porta_read <= '0';
portb_read <= '0';
when others =>
null;
end case;
end process;
--* Write I/O ports
--*
pia_write : process( clk, rst, addr, cs, rw, data_in,
porta_ctrl, portb_ctrl,
porta_data, portb_data,
porta_ctrl, portb_ctrl,
porta_ddr, portb_ddr )
begin
if rst = '1' then
porta_ddr <= "00000000";
porta_data <= "00000000";
porta_ctrl <= "000000";
portb_ddr <= "00000000";
portb_data <= "00000000";
portb_ctrl <= "000000";
portb_write <= '0';
elsif clk'event and clk = '1' then
if cs = '1' and rw = '0' then
case addr is
when "00" =>
if porta_ctrl(2) = '0' then
porta_ddr <= data_in;
porta_data <= porta_data;
else
porta_ddr <= porta_ddr;
porta_data <= data_in;
end if;
porta_ctrl <= porta_ctrl;
portb_ddr <= portb_ddr;
portb_data <= portb_data;
portb_ctrl <= portb_ctrl;
portb_write <= '0';
when "01" =>
porta_ddr <= porta_ddr;
porta_data <= porta_data;
porta_ctrl <= data_in(5 downto 0);
portb_ddr <= portb_ddr;
portb_data <= portb_data;
portb_ctrl <= portb_ctrl;
portb_write <= '0';
when "10" =>
porta_ddr <= porta_ddr;
porta_data <= porta_data;
porta_ctrl <= porta_ctrl;
if portb_ctrl(2) = '0' then
portb_ddr <= data_in;
portb_data <= portb_data;
portb_write <= '0';
else
portb_ddr <= portb_ddr;
portb_data <= data_in;
portb_write <= '1';
end if;
portb_ctrl <= portb_ctrl;
when "11" =>
porta_ddr <= porta_ddr;
porta_data <= porta_data;
porta_ctrl <= porta_ctrl;
portb_ddr <= portb_ddr;
portb_data <= portb_data;
portb_ctrl <= data_in(5 downto 0);
portb_write <= '0';
when others =>
porta_ddr <= porta_ddr;
porta_data <= porta_data;
porta_ctrl <= porta_ctrl;
portb_ddr <= portb_ddr;
portb_data <= portb_data;
portb_ctrl <= portb_ctrl;
portb_write <= '0';
end case;
else
porta_ddr <= porta_ddr;
porta_data <= porta_data;
porta_ctrl <= porta_ctrl;
portb_data <= portb_data;
portb_ddr <= portb_ddr;
portb_ctrl <= portb_ctrl;
portb_write <= '0';
end if;
end if;
end process;
--* CA1 Edge detect
ca1_input : process( clk, rst, ca1, ca1_del,
ca1_rise, ca1_fall, ca1_edge,
irqa1, porta_ctrl, porta_read )
begin
if rst = '1' then
ca1_del <= '0';
ca1_rise <= '0';
ca1_fall <= '0';
ca1_edge <= '0';
irqa1 <= '0';
elsif clk'event and clk = '0' then
ca1_del <= ca1;
ca1_rise <= (not ca1_del) and ca1;
ca1_fall <= ca1_del and (not ca1);
if ca1_edge = '1' then
irqa1 <= '1';
elsif porta_read = '1' then
irqa1 <= '0';
else
irqa1 <= irqa1;
end if;
end if;
if porta_ctrl(1) = '0' then
ca1_edge <= ca1_fall;
else
ca1_edge <= ca1_rise;
end if;
end process;
--* CA2 Edge detect
ca2_input : process( clk, rst, ca2, ca2_del,
ca2_rise, ca2_fall, ca2_edge,
irqa2, porta_ctrl, porta_read )
begin
if rst = '1' then
ca2_del <= '0';
ca2_rise <= '0';
ca2_fall <= '0';
ca2_edge <= '0';
irqa2 <= '0';
elsif clk'event and clk = '0' then
ca2_del <= ca2;
ca2_rise <= (not ca2_del) and ca2;
ca2_fall <= ca2_del and (not ca2);
if porta_ctrl(5) = '0' and ca2_edge = '1' then
irqa2 <= '1';
elsif porta_read = '1' then
irqa2 <= '0';
else
irqa2 <= irqa2;
end if;
end if;
if porta_ctrl(4) = '0' then
ca2_edge <= ca2_fall;
else
ca2_edge <= ca2_rise;
end if;
end process;
--* CA2 output control
ca2_output : process( clk, rst, porta_ctrl, porta_read, ca1_edge, ca2_out )
begin
if rst='1' then
ca2_out <= '0';
elsif clk'event and clk='0' then
case porta_ctrl(5 downto 3) is
when "100" => -- read PA clears, CA1 edge sets
if porta_read = '1' then
ca2_out <= '0';
elsif ca1_edge = '1' then
ca2_out <= '1';
else
ca2_out <= ca2_out;
end if;
when "101" => -- read PA clears, E sets
ca2_out <= not porta_read;
when "110" => -- set low
ca2_out <= '0';
when "111" => -- set high
ca2_out <= '1';
when others => -- no change
ca2_out <= ca2_out;
end case;
end if;
end process;
--* CB1 Edge detect
cb1_input : process( clk, rst, cb1, cb1_del,
cb1_rise, cb1_fall, cb1_edge,
irqb1, portb_ctrl, portb_read )
begin
if rst = '1' then
cb1_del <= '0';
cb1_rise <= '0';
cb1_fall <= '0';
cb1_edge <= '0';
irqb1 <= '0';
elsif clk'event and clk = '0' then
cb1_del <= cb1;
cb1_rise <= (not cb1_del) and cb1;
cb1_fall <= cb1_del and (not cb1);
if cb1_edge = '1' then
irqb1 <= '1';
elsif portb_read = '1' then
irqb1 <= '0';
else
irqb1 <= irqb1;
end if;
end if;
if portb_ctrl(1) = '0' then
cb1_edge <= cb1_fall;
else
cb1_edge <= cb1_rise;
end if;
end process;
--* CB2 Edge detect
cb2_input : process( clk, rst, cb2, cb2_del,
cb2_rise, cb2_fall, cb2_edge,
irqb2, portb_ctrl, portb_read )
begin
if rst = '1' then
cb2_del <= '0';
cb2_rise <= '0';
cb2_fall <= '0';
cb2_edge <= '0';
irqb2 <= '0';
elsif clk'event and clk = '0' then
cb2_del <= cb2;
cb2_rise <= (not cb2_del) and cb2;
cb2_fall <= cb2_del and (not cb2);
if portb_ctrl(5) = '0' and cb2_edge = '1' then
irqb2 <= '1';
elsif portb_read = '1' then
irqb2 <= '0';
else
irqb2 <= irqb2;
end if;
end if;
if portb_ctrl(4) = '0' then
cb2_edge <= cb2_fall;
else
cb2_edge <= cb2_rise;
end if;
end process;
--* CB2 output control
cb2_output : process( clk, rst, portb_ctrl, portb_write, cb1_edge, cb2_out )
begin
if rst='1' then
cb2_out <= '0';
elsif clk'event and clk='0' then
case portb_ctrl(5 downto 3) is
when "100" => -- write PB clears, CA1 edge sets
if portb_write = '1' then
cb2_out <= '0';
elsif cb1_edge = '1' then
cb2_out <= '1';
else
cb2_out <= cb2_out;
end if;
when "101" => -- write PB clears, E sets
cb2_out <= not portb_write;
when "110" => -- set low
cb2_out <= '0';
when "111" => -- set high
cb2_out <= '1';
when others => -- no change
cb2_out <= cb2_out;
end case;
end if;
end process;
--* IRQ control
pia_irq : process( irqa1, irqa2, irqb1, irqb2, porta_ctrl, portb_ctrl )
begin
irqa <= (irqa1 and porta_ctrl(0)) or (irqa2 and porta_ctrl(3));
irqb <= (irqb1 and portb_ctrl(0)) or (irqb2 and portb_ctrl(3));
end process;
--* 2 x 74193 binary down counter
--*
--* On the reference 6809 board,
--* RTI takes one more clock cycle than System09.
--* So subtract 1 from the porta_data preset value.
--*
--* 11th July 2006 John Kent:
--* RTI in CPU09 has been extended by one bus cycle
--* so remove the subtract by one offset on porta_data
pia_counter : process( clk, timer, porta_data, ca2_out, cb2_out)
begin
if cb2_out = '1' then
timer <= "00000000";
elsif ca2_out = '0' then
-- timer <= porta_data - "00000001";
timer <= porta_data;
elsif clk'event and clk='1' then
timer <= timer - "00000001";
end if;
pa <= "00000000";
pb <= timer;
ca1 <= timer(7);
cb1 <= timer(7);
ca2 <= '0';
cb2 <= '0';
end process;
end pia_arch;