-- Copyright (c)2006, 2016, 2019 Jeremy Seth Henry
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-- Copyright (c)2006, 2016, 2019, 2020 Jeremy Seth Henry
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-- All rights reserved.
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-- All rights reserved.
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--
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--
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-- Redistribution and use in source and binary forms, with or without
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-- Redistribution and use in source and binary forms, with or without
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-- modification, are permitted provided that the following conditions are met:
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-- modification, are permitted provided that the following conditions are met:
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-- * Redistributions of source code must retain the above copyright
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-- * Redistributions of source code must retain the above copyright
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-- notice, this list of conditions and the following disclaimer.
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-- notice, this list of conditions and the following disclaimer.
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-- * Redistributions in binary form must reproduce the above copyright
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-- * Redistributions in binary form must reproduce the above copyright
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-- notice, this list of conditions and the following disclaimer in the
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-- notice, this list of conditions and the following disclaimer in the
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-- documentation and/or other materials provided with the distribution,
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-- documentation and/or other materials provided with the distribution,
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-- where applicable (as part of a user interface, debugging port, etc.)
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-- where applicable (as part of a user interface, debugging port, etc.)
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--
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--
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-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY
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-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY
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-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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-- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY
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-- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY
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-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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-- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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--
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--
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-- VHDL Units : o8_sys_timer
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-- VHDL Units : o8_sys_timer
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-- Description: Provides an 8-bit microsecond resolution timer for generating
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-- Description: Provides an 8-bit microsecond resolution timer for generating
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-- : periodic interrupts for the Open8 CPU.
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-- : periodic interrupts for the Open8 CPU.
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--
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--
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-- Notes : It is possible to set the value to zero, resulting in the
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-- Notes : It is possible to set the value to zero, resulting in the
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-- : output staying high indefinitely. This may cause an issue if
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-- : output staying high indefinitely. This may cause an issue if
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-- : the output is connected to an interrupt input.
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-- : the output is connected to an interrupt input.
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-- : Also provides uSec_Tick as an output
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-- : Also provides uSec_Tick as an output
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--
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--
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-- Revision History
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-- Revision History
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-- Author Date Change
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-- Author Date Change
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------------------ -------- ---------------------------------------------------
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------------------ -------- ---------------------------------------------------
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-- Seth Henry 07/28/11 Design Start
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-- Seth Henry 07/28/11 Design Start
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-- Seth Henry 12/19/19 Renamed Tmr_Out to Interrupt
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-- Seth Henry 12/19/19 Renamed Tmr_Out to Interrupt
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library ieee;
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_misc.all;
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use ieee.std_logic_misc.all;
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library work;
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library work;
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use work.open8_pkg.all;
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use work.open8_pkg.all;
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entity o8_sys_timer is
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entity o8_sys_timer is
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generic(
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generic(
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Sys_Freq : real;
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Sys_Freq : real;
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Reset_Level : std_logic;
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Reset_Level : std_logic;
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Address : ADDRESS_TYPE
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Address : ADDRESS_TYPE
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);
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);
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port(
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port(
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Clock : in std_logic;
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Clock : in std_logic;
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Reset : in std_logic;
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Reset : in std_logic;
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uSec_Tick : out std_logic;
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uSec_Tick : out std_logic;
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--
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--
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Bus_Address : in ADDRESS_TYPE;
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Bus_Address : in ADDRESS_TYPE;
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Wr_Enable : in std_logic;
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Wr_Enable : in std_logic;
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Wr_Data : in DATA_TYPE;
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Wr_Data : in DATA_TYPE;
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Rd_Enable : in std_logic;
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Rd_Enable : in std_logic;
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Rd_Data : out DATA_TYPE;
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Rd_Data : out DATA_TYPE;
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Interrupt : out std_logic
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Interrupt : out std_logic
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);
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);
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end entity;
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end entity;
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architecture behave of o8_sys_timer is
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architecture behave of o8_sys_timer is
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constant User_Addr : ADDRESS_TYPE := Address;
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constant User_Addr : ADDRESS_TYPE := Address;
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alias Comp_Addr is Bus_Address(15 downto 0);
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alias Comp_Addr is Bus_Address(15 downto 0);
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signal Addr_Match : std_logic := '0';
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signal Addr_Match : std_logic := '0';
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signal Wr_En : std_logic := '0';
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signal Wr_En : std_logic := '0';
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signal Wr_Data_q : DATA_TYPE := OPEN8_NULLBUS;
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signal Wr_Data_q : DATA_TYPE := OPEN8_NULLBUS;
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signal Rd_En : std_logic := '0';
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signal Rd_En : std_logic := '0';
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signal Rd_En_q : std_logic := '0';
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signal Rd_En_q : std_logic := '0';
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signal Interval : DATA_TYPE := x"00";
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signal Interval : DATA_TYPE := x"00";
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signal Timer_Cnt : DATA_TYPE := x"00";
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signal Timer_Cnt : DATA_TYPE := x"00";
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constant DLY_1USEC_VAL: integer := integer(Sys_Freq / 1000000.0);
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constant DLY_1USEC_VAL: integer := integer(Sys_Freq / 1000000.0);
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constant DLY_1USEC_WDT: integer := ceil_log2(DLY_1USEC_VAL - 1);
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constant DLY_1USEC_WDT: integer := ceil_log2(DLY_1USEC_VAL - 1);
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constant DLY_1USEC : std_logic_vector :=
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constant DLY_1USEC : std_logic_vector :=
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conv_std_logic_vector(DLY_1USEC_VAL - 1, DLY_1USEC_WDT);
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conv_std_logic_vector(DLY_1USEC_VAL - 1, DLY_1USEC_WDT);
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signal uSec_Cntr : std_logic_vector( DLY_1USEC_WDT - 1 downto 0 )
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signal uSec_Cntr : std_logic_vector( DLY_1USEC_WDT - 1 downto 0 )
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:= (others => '0');
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:= (others => '0');
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signal uSec_Tick_i : std_logic := '0';
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signal uSec_Tick_i : std_logic := '0';
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begin
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begin
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uSec_Tick <= uSec_Tick_i;
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uSec_Tick <= uSec_Tick_i;
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Addr_Match <= '1' when Comp_Addr = User_Addr else '0';
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Addr_Match <= '1' when Comp_Addr = User_Addr else '0';
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io_reg: process( Clock, Reset )
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io_reg: process( Clock, Reset )
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begin
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begin
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if( Reset = Reset_Level )then
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if( Reset = Reset_Level )then
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Wr_En <= '0';
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Wr_En <= '0';
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Wr_Data_q <= x"00";
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Wr_Data_q <= x"00";
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Rd_En <= '0';
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Rd_En <= '0';
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Rd_Data <= OPEN8_NULLBUS;
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Rd_Data <= OPEN8_NULLBUS;
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Interval <= x"00";
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Interval <= x"00";
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elsif( rising_edge( Clock ) )then
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elsif( rising_edge( Clock ) )then
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Wr_En <= Addr_Match and Wr_Enable;
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Wr_En <= Addr_Match and Wr_Enable;
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Wr_Data_q <= Wr_Data;
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Wr_Data_q <= Wr_Data;
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if( Wr_En = '1' )then
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if( Wr_En = '1' )then
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Interval <= Wr_Data_q;
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Interval <= Wr_Data_q;
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end if;
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end if;
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Rd_Data <= (others => '0');
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Rd_Data <= (others => '0');
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Rd_En <= Addr_Match and Rd_Enable;
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Rd_En <= Addr_Match and Rd_Enable;
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if( Rd_En = '1' )then
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if( Rd_En = '1' )then
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Rd_Data <= Interval;
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Rd_Data <= Interval;
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end if;
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end if;
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end if;
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end if;
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end process;
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end process;
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uSec_Tick_i_proc: process( Clock, Reset )
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uSec_Tick_i_proc: process( Clock, Reset )
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begin
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begin
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if( Reset = Reset_Level )then
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if( Reset = Reset_Level )then
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uSec_Cntr <= (others => '0');
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uSec_Cntr <= (others => '0');
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uSec_Tick_i <= '0';
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uSec_Tick_i <= '0';
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elsif( rising_edge( Clock ) )then
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elsif( rising_edge( Clock ) )then
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uSec_Cntr <= uSec_Cntr - 1;
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uSec_Cntr <= uSec_Cntr - 1;
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uSec_Tick_i <= '0';
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uSec_Tick_i <= '0';
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if( uSec_Cntr = 0 )then
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if( uSec_Cntr = 0 )then
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uSec_Cntr <= DLY_1USEC;
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uSec_Cntr <= DLY_1USEC;
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uSec_Tick_i <= '1';
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uSec_Tick_i <= '1';
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end if;
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end if;
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end if;
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end if;
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end process;
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end process;
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Interval_proc: process( Clock, Reset )
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Interval_proc: process( Clock, Reset )
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begin
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begin
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if( Reset = Reset_Level )then
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if( Reset = Reset_Level )then
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Timer_Cnt <= x"00";
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Timer_Cnt <= x"00";
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Interrupt <= '0';
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Interrupt <= '0';
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elsif( rising_edge(Clock) )then
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elsif( rising_edge(Clock) )then
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Interrupt <= '0';
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Interrupt <= '0';
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Timer_Cnt <= Timer_Cnt - uSec_Tick_i;
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Timer_Cnt <= Timer_Cnt - uSec_Tick_i;
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if( or_reduce(Timer_Cnt) = '0' )then
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if( or_reduce(Timer_Cnt) = '0' )then
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Timer_Cnt <= Interval;
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Timer_Cnt <= Interval;
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Interrupt <= or_reduce(Interval); -- Only trigger on Int > 0
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Interrupt <= or_reduce(Interval); -- Only trigger on Int > 0
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end if;
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end if;
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end if;
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end if;
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end process;
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end process;
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end architecture;
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end architecture;
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