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Gehstock.Mist_FPGA/common/CPU/t48/int.vhd
Gehstock 3656363a3c Some work on Donkey Kong + Clean up
2020-05-13 15:54:31 +02:00

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-------------------------------------------------------------------------------
--
-- The Interrupt Controller.
-- It collects the interrupt sources and notifies the decoder.
--
-- $Id: int.vhd,v 1.7 2006/06/20 00:46:03 arniml Exp $
--
-- Copyright (c) 2004, Arnim Laeuger (arniml@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/t48/
--
-------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use work.t48_pack.mstate_t;
entity t48_int is
port (
clk_i : in std_logic;
res_i : in std_logic;
en_clk_i : in boolean;
xtal_i : in std_logic;
xtal_en_i : in boolean;
clk_mstate_i : in mstate_t;
jtf_executed_i : in boolean;
tim_overflow_i : in boolean;
tf_o : out std_logic;
en_tcnti_i : in boolean;
dis_tcnti_i : in boolean;
int_n_i : in std_logic;
ale_i : in boolean;
last_cycle_i : in boolean;
en_i_i : in boolean;
dis_i_i : in boolean;
ext_int_o : out boolean;
tim_int_o : out boolean;
retr_executed_i : in boolean;
int_executed_i : in boolean;
int_pending_o : out boolean;
int_in_progress_o : out boolean
);
end t48_int;
use work.t48_pack.all;
architecture rtl of t48_int is
constant tim_int_c : std_logic := '0';
constant ext_int_c : std_logic := '1';
type int_state_t is (IDLE, PENDING, INT);
signal int_state_s,
int_state_q : int_state_t;
signal timer_flag_q : boolean;
signal timer_overflow_q : boolean;
signal timer_int_enable_q : boolean;
signal int_q : boolean;
signal int_enable_q : boolean;
signal ale_q : boolean;
signal int_type_q : std_logic;
signal int_in_progress_q : boolean;
begin
-----------------------------------------------------------------------------
-- Process nstate
--
-- Purpose:
-- Determines the next state of the Interrupt controller FSM.
--
nstate: process (int_state_q,
int_type_q,
int_in_progress_q,
int_executed_i,
retr_executed_i,
clk_mstate_i,
last_cycle_i)
begin
int_state_s <= int_state_q;
case int_state_q is
when IDLE =>
if int_in_progress_q and
last_cycle_i and clk_mstate_i = MSTATE5 then
int_state_s <= PENDING;
end if;
when PENDING =>
if int_executed_i then
int_state_s <= INT;
end if;
when INT =>
if retr_executed_i then
int_state_s <= IDLE;
end if;
when others =>
int_state_s <= IDLE;
end case;
end process nstate;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process regs
--
-- Purpose:
-- Implement the various registers.
-- They are designed according Figure "Interrupt Logic" of
-- "The Single Component MCS-48 System".
--
regs: process (res_i, clk_i)
begin
if res_i = res_active_c then
timer_flag_q <= false;
timer_overflow_q <= false;
timer_int_enable_q <= false;
int_enable_q <= false;
int_type_q <= '0';
int_state_q <= IDLE;
int_in_progress_q <= false;
elsif clk_i'event and clk_i = clk_active_c then
if en_clk_i then
int_state_q <= int_state_s;
if jtf_executed_i then
timer_flag_q <= false;
elsif tim_overflow_i then
timer_flag_q <= true;
end if;
if (int_type_q = tim_int_c and int_executed_i) or
not timer_int_enable_q then
timer_overflow_q <= false;
elsif tim_overflow_i then
timer_overflow_q <= true;
end if;
if dis_tcnti_i then
timer_int_enable_q <= false;
elsif en_tcnti_i then
timer_int_enable_q <= true;
end if;
if dis_i_i then
int_enable_q <= false;
elsif en_i_i then
int_enable_q <= true;
end if;
if retr_executed_i then
int_in_progress_q <= false;
elsif (int_q and int_enable_q) or
timer_overflow_q then
int_in_progress_q <= true;
if not int_in_progress_q then
int_type_q <= to_stdLogic(int_q and int_enable_q);
end if;
end if;
end if;
end if;
end process regs;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process xtal_regs
--
-- Purpose:
-- Implements the sequential registers clocked with XTAL.
--
xtal_regs: process (res_i, xtal_i)
begin
if res_i = res_active_c then
int_q <= false;
ale_q <= false;
elsif xtal_i'event and xtal_i = clk_active_c then
if xtal_en_i then
ale_q <= ale_i;
if last_cycle_i and
ale_q and not ale_i then
int_q <= not to_boolean(int_n_i);
end if;
end if;
end if;
end process xtal_regs;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Output Mapping.
-----------------------------------------------------------------------------
tf_o <= to_stdLogic(timer_flag_q);
ext_int_o <= int_type_q = ext_int_c;
tim_int_o <= int_type_q = tim_int_c;
int_pending_o <= int_state_q = PENDING;
int_in_progress_o <= int_in_progress_q and int_state_q /= IDLE;
end rtl;
-------------------------------------------------------------------------------
-- File History:
--
-- $Log: int.vhd,v $
-- Revision 1.7 2006/06/20 00:46:03 arniml
-- new input xtal_en_i
--
-- Revision 1.6 2005/11/01 21:26:24 arniml
-- operate ale_q and int_q with xtal_i after shift of ALE assertion to XTAL3
--
-- Revision 1.5 2005/09/13 21:00:16 arniml
-- Fix bug reports:
-- "Target address of JMP to Program Memory Bank 1 corrupted by interrupt"
-- "Return address of CALL to Program Memory Bank 1 corrupted by interrupt"
-- int_in_progress_o was active one cycle before int_pending_o is
-- asserted. this confused the mb multiplexer which determines the state of
-- the memory bank selection flag
--
-- Revision 1.4 2005/06/11 10:08:43 arniml
-- introduce prefix 't48_' for all packages, entities and configurations
--
-- Revision 1.3 2004/07/11 16:51:33 arniml
-- cleanup copyright notice
--
-- Revision 1.2 2004/06/30 21:18:28 arniml
-- Fix bug report:
-- "Program Memory bank can be switched during interrupt"
-- int module emits int_in_progress signal that is used inside the decoder
-- to hold mb low for JMP and CALL during interrupts
--
-- Revision 1.1 2004/03/23 21:31:52 arniml
-- initial check-in
--
-------------------------------------------------------------------------------
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