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lal87 |
----------------------------------------------------------------------------
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---- Create Date: 00:12:45 10/23/2010
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---- Design Name: pic
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---- Project Name: PIC
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Description:
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---- A Programmable Interrupt Controller which can handle upto 8 ----
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---- level triggered interrupts.The operating modes available are ----
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---- polling fixed priority modes. ---- ----
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----------------------------------------------------------------------------
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---- ----
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---- This file is a part of the pic project at ----
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---- http://www.opencores.org/ ----
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---- ----
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---- Author(s): ----
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---- Vipin Lal, lalnitt@gmail.com ----
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---- ----
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----------------------------------------------------------------------------
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---- ----
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---- Copyright (C) 2010 Authors and OPENCORES.ORG ----
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---- ----
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---- This source file may be used and distributed without ----
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---- restriction provided that this copyright statement is not ----
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---- removed from the file and that any derivative work contains ----
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---- the original copyright notice and the associated disclaimer. ----
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---- ----
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---- This source file is free software; you can redistribute it ----
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---- and/or modify it under the terms of the GNU Lesser General ----
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---- Public License as published by the Free Software Foundation; ----
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---- either version 2.1 of the License, or (at your option) any ----
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---- later version. ----
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---- ----
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---- This source is distributed in the hope that it will be ----
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---- useful, but WITHOUT ANY WARRANTY; without even the implied ----
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---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ----
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---- PURPOSE. See the GNU Lesser General Public License for more ----
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---- details. ----
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---- ----
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---- You should have received a copy of the GNU Lesser General ----
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---- Public License along with this source; if not, download it ----
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---- from http://www.opencores.org/lgpl.shtml ----
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---- ----
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----------------------------------------------------------------------------
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library IEEE;
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use IEEE.STD_LOGIC_1164.ALL;
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use IEEE.NUMERIC_STD.ALL;
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entity PIC is
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port( CLK_I : in std_logic; --Clock.
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RST_I : in std_logic; --Reset
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IR : in unsigned(7 downto 0); --Interrupt requests from peripherals.
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DataBus : inout unsigned(7 downto 0); --Data bus between processor PIC.
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INTR_O : out std_logic; --Interrupt Request pin of processor.
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INTA_I : in std_logic --Interrupt ack.
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);
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end PIC;
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architecture Behavioral of PIC is
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type state_type is (reset_s,get_commands,jump_int_method,start_polling,tx_int_info_polling,ack_ISR_done,
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ack_txinfo_rxd,start_priority_check,tx_int_info_priority,ack_txinfo_rxd_priority,ack_ISR_done_pt);
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signal next_s : state_type :=reset_s;
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signal int_type : unsigned(1 downto 0):="01";
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signal int_index,count_cmd : integer := 0;
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type prior_table is array (0 to 7) of unsigned(2 downto 0);
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signal pt : prior_table := (others => (others => '0'));
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signal int_pt : unsigned(2 downto 0):="000";
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signal flag,flag1 : std_logic := '0'; --These flags are used for timing purposes.
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begin
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process(CLK_I,RST_I)
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begin
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if( RST_I = '1') then
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next_s <= reset_s;
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elsif( rising_edge(CLK_I) ) then
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flag <= INTA_I;
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case next_s is
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when reset_s =>
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--initialze signals to zero.
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flag <= '0';
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flag1 <= '0';
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int_type <= "00";
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int_index <= 0;
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count_cmd <= 0;
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int_pt <= "000";
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pt <= (others => (others => '0'));
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if( RST_I = '0' ) then
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next_s <= get_commands;
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else
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next_s <= reset_s;
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end if;
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DataBus <= (others => 'Z');
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when get_commands => --Get commands and operating mode from the processor.
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if( DataBus(1 downto 0) = "01" ) then
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int_type <= "01";
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next_s <= jump_int_method;
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elsif( DataBus(1 downto 0) = "10" and count_cmd = 0) then
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pt(0) <= DataBus(7 downto 5);
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pt(1) <= DataBus(4 downto 2);
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count_cmd <= count_cmd + 1;
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next_s <= get_commands;
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elsif( DataBus(1 downto 0) = "10" and count_cmd = 1) then
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pt(2) <= DataBus(7 downto 5);
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pt(3) <= DataBus(4 downto 2);
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count_cmd <= count_cmd + 1;
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next_s <= get_commands;
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elsif( DataBus(1 downto 0) = "10" and count_cmd = 2) then
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pt(4) <= DataBus(7 downto 5);
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pt(5) <= DataBus(4 downto 2);
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count_cmd <= count_cmd + 1;
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next_s <= get_commands;
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elsif( DataBus(1 downto 0) = "10" and count_cmd = 3) then
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pt(6) <= DataBus(7 downto 5);
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pt(7) <= DataBus(4 downto 2);
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count_cmd <= 0;
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int_type <= "10";
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next_s <= jump_int_method;
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else
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next_s <= get_commands;
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end if;
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when jump_int_method => --Check which method is used to determine the interrupts.
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flag <= '0';
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flag1 <= '0';
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int_index <= 0;
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count_cmd <= 0;
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int_pt <= "000";
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if( int_type = "01" ) then
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next_s <= start_polling; --Polling method for checking the interrupts.
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elsif( int_type = "10" ) then
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next_s <= start_priority_check; --Fixed priority scheme.
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else
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next_s <= reset_s; --Error if no method is specified.
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end if;
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DataBus <= (others => 'Z');
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when start_polling => --Check for interrupts(one by one) using polling method.
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if( IR(int_index) = '1' ) then
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INTR_O <= '1';
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next_s <= tx_int_info_polling;
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else
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INTR_O <= '0';
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end if;
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if( int_index = 7 ) then
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int_index <= 0;
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else
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int_index <= int_index+1;
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end if;
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DataBus <= (others => 'Z');
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when tx_int_info_polling => --Transmit interrupt information if an interrupt is found.
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if( INTA_I = '0' ) then
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INTR_O <= '0';
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end if;
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if( flag = '0' ) then
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DataBus <= "01011" & to_unsigned( (int_index-1),3); --MSB "01011" is for matching purpose.
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flag1 <= '1';
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else
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flag1 <= '0';
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end if;
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if ( flag1 = '1' ) then
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next_s <= ack_txinfo_rxd;
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if( INTA_I = '0' ) then
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DataBus <= (others => 'Z');
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end if;
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end if;
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when ack_txinfo_rxd => --ACK send by processor to tell PIC that interrupt info is received correctly.
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if( INTA_I <= '0' ) then
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next_s <= ack_ISR_done;
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DataBus <= (others => 'Z');
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end if;
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when ack_ISR_done => --Wait for the ISR for the particular interrupt to get over.
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if( INTA_I = '0' and DataBus(7 downto 3) = "10100" and DataBus(2 downto 0) = to_unsigned(int_index-1,3) ) then
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next_s <= start_polling;
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else
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next_s <= ack_ISR_done;
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end if;
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when start_priority_check => --Fixed priority method for interrupt handling.
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--Interrupts are checked based on their priority.
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if( IR(to_integer(pt(0))) = '1' ) then
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int_pt <= pt(0);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(1))) = '1' ) then
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int_pt <= pt(1);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(2))) = '1' ) then
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int_pt <= pt(2);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(3))) = '1' ) then
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int_pt <= pt(3);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(4))) = '1' ) then
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int_pt <= pt(4);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(5))) = '1' ) then
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int_pt <= pt(5);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(6))) = '1' ) then
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int_pt <= pt(6);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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elsif( IR(to_integer(pt(7))) = '1' ) then
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int_pt <= pt(7);
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INTR_O <= '1';
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next_s <= tx_int_info_priority;
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else
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next_s <= start_priority_check;
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end if;
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DataBus <= (others => 'Z');
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when tx_int_info_priority => --Transmit interrupt information if an interrupt is found.
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if( INTA_I = '0' ) then
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INTR_O <= '0';
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end if;
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if( flag = '0' ) then
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DataBus <= "10011" & int_pt; --MSB "10011" is for matching purpose.
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flag1 <= '1';
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else
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flag1 <= '0';
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end if;
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if ( flag1 = '1' ) then
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next_s <= ack_txinfo_rxd_priority;
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if( INTA_I = '0' ) then
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DataBus <= (others => 'Z');
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end if;
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end if;
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when ack_txinfo_rxd_priority => --ACK send by processor to tell PIC that interrupt info is received correctly.
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if( INTA_I <= '0' ) then
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next_s <= ack_ISR_done_pt;
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DataBus <= (others => 'Z');
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end if;
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when ack_ISR_done_pt => --Wait for the ISR for the particular interrupt to get over.
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if( INTA_I = '0' and DataBus(7 downto 3) = "01100" and DataBus(2 downto 0) = int_pt ) then
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next_s <= start_priority_check;
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elsif( DataBus(7 downto 3) /= "01100" or DataBus(2 downto 0) /= int_pt ) then
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next_s <= reset_s; --Error.
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else
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next_s <= ack_ISR_done_pt;
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end if;
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when others =>
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DataBus <= (others => 'Z');
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end case;
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end if;
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end process;
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end Behavioral;
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