Subversion Repositories raytrac

--! @file im.vhd

--! @brief Maquina de Interrupciones. Circuito que detecta eventos que generan interrupciones para que el usuario externo del RayTrac detecte eventos como el final de una instrucción.  

--! @author Julián Andrés Guarín Reyes

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

-- RAYTRAC

-- Author Julian Andres Guarin

-- sm.vhd

-- This file is part of raytrac.

-- 

--     raytrac 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.

-- 

--     raytrac 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 raytrac.  If not, see <http://www.gnu.org/licenses/>.

--! 

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use work.arithpack.all;

entity im is

        generic (

                num_events : integer :=4;

                cycles_to_wait : integer := 1023

        );

        port (

                clk,rst:                in std_logic;

                rfull_event:    in std_logic;

                eoi_event:              in std_logic;   --! end of instruction related events

                int:                    out std_logic;  --! interruption

                state:                  out iCtrlState

        );

end entity;

architecture im_arch of im is

        signal s_state : iCtrlState;

begin

        state <= s_state;

        --! Existen 2 estados para disparar la señal de interrupción : WAITING_FOR_A_RFULL_EVENT y INHIBIT_RFULL_INT. Siempre que haya el final de una instrucción en cualquiera de los dos estados se notificará el evento sin importar el estado en que se encuentre la máquina.

        --! Si cualquiera de las señales de cola llena se encuentra activa, el evento será notificado en el estado WAITING_FOR_A_RFULL_EVENT, inmediatamente se cambia al estado INHIBIT_RFULL_INT, donde durante un n&uacte;mero de ciclos (parametrizado) se ignora la señal de full de las colas de resultados.

        --! Despues que han transcurrido los ciclos mencionados, se vuelve al estado WAITING_FOR_A_RFULL_EVENT.

        sm_proc:

        process (clk,rst)

                variable tempo : integer range 0 to cycles_to_wait:=cycles_to_wait;

        begin

                if rst=rstMasterValue then

                        tempo := cycles_to_wait;

                        int <= '0';

                elsif clk'event and clk='1' then

                        case s_state is

                                when WAITING_FOR_A_RFULL_EVENT =>

                                        int <= rfull_event or eoi_event;

                                        if rfull_event='1' then

                                                s_state <= INHIBIT_RFULL_INT;

                                        end if;

                                when INHIBIT_RFULL_INT =>

                                        int <= eoi_event;

                                        if tempo=0 then

                                                s_state <= WAITING_FOR_A_RFULL_EVENT;

                                                tempo := cycles_to_wait;

                                        else

                                                tempo:=tempo-1;

                                        end if;

                                when others => null;

                        end case;

                end if;

        end process;

end architecture;