Subversion Repositories cpu65c02_true_cycle

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.std_logic_arith.all;

entity fsm_intnmi is

   port(

      clk_clk_i   : in     std_logic;

      nmi_n_i     : in     std_logic;

      rst_nmi_i   : in     std_logic;

      rst_rst_n_i : in     std_logic;

      nmi_o       : out    std_logic

   );

-- Declarations

end fsm_intnmi ;

-- (C) 2008 - 2021 Jens Gutschmidt

-- (email: opencores@vivare-services.com)

-- 

-- Versions:

-- Revision 1.8  2018/09/01 18:07:00  jens

-- - NMI = '0' need at least 1 cycles for correct

--   operation now (2 cycles in the past)

-- 

-- Revision 1.7  2013/07/21 11:11:00  jens

-- - Changing the title block and internal revision history

-- 

-- Revision 1.6  2009/01/04 10:20:47  eda

-- Changes for cosmetic issues only

-- 

-- Revision 1.5  2009/01/04 09:23:10  eda

-- - Delete unused nets and blocks (same as R6502_TC)

-- - Rename blocks

-- 

-- Revision 1.4  2009/01/03 16:53:02  eda

-- - Unused nets and blocks deleted

-- - Renamed blocks

-- 

-- Revision 1.3  2009/01/03 16:42:02  eda

-- - Unused nets and blocks deleted

-- - Renamed blocks

-- 

-- Revision 1.2  2008/12/31 19:31:24  eda

-- Production Release

--  

-- 

--

-- r65c02_tc.fsm_intnmi.fsm

--

-- Date:    09.01.2021

-- Time:    16:57:49

-- By:        VIVARE GmbH, Switzerland

--

-- COPYRIGHT (C) 2008 - 2021 by Jens Gutschmidt

-- 

-- 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 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/>.

-- 

-- 

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.std_logic_arith.all;

architecture fsm of fsm_intnmi is

   type state_type is (

      idle,

      idle1,

      IMP

   );

   -- State vector declaration

   attribute state_vector : string;

   attribute state_vector of fsm : architecture is "current_state";

   -- Declare current and next state signals

   signal current_state : state_type;

   signal next_state : state_type;

   -- Declare any pre-registered internal signals

   signal nmi_o_cld : std_logic ;

begin

   -----------------------------------------------------------------

   clocked_proc : process (

      clk_clk_i,

      rst_rst_n_i

   )

   -----------------------------------------------------------------

   begin

      if (rst_rst_n_i = '0') then

         current_state <= idle;

         -- Default Reset Values

         nmi_o_cld <= '0';

      elsif (clk_clk_i'event and clk_clk_i = '1') then

         current_state <= next_state;

         -- Default Assignment To Internals

         nmi_o_cld <= '0';

         -- Combined Actions

         case current_state is

            when idle1 =>

               if (nmi_n_i = '0') then

                  nmi_o_cld <= '1';

               end if;

            when IMP =>

               nmi_o_cld <= '1';

               if (rst_nmi_i = '1') then

                  nmi_o_cld <= '0';

               end if;

            when others =>

               null;

         end case;

      end if;

   end process clocked_proc;

   -----------------------------------------------------------------

   nextstate_proc : process (

      current_state,

      nmi_n_i,

      rst_nmi_i

   )

   -----------------------------------------------------------------

   begin

      case current_state is

         when idle =>

            if (nmi_n_i = '1') then

               next_state <= idle1;

            else

               next_state <= idle;

            end if;

         when idle1 =>

            if (nmi_n_i = '0') then

               next_state <= IMP;

            else

               next_state <= idle1;

            end if;

         when IMP =>

            if (rst_nmi_i = '1') then

               next_state <= idle;

            else

               next_state <= IMP;

            end if;

         when others =>

            next_state <= idle;

      end case;

   end process nextstate_proc;

   -- Concurrent Statements

   -- Clocked output assignments

   nmi_o <= nmi_o_cld;

end fsm;