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jshamlet |
-- Copyright (c)2020 Jeremy Seth Henry
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-- All rights reserved.
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--
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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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-- * 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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-- * 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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-- 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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--
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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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-- 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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-- 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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-- 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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-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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-- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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--
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-- VHDL Entity: o8_vector_rx
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-- Description: Receives a 6-bit vector command and 16-bit argument from the
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-- vector_tx entity. Issues interrupt to the CPU on receipt of
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-- three bytes.
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--
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-- Register Map:
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-- Offset Bitfield Description Read/Write
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-- 0x0 --AAAAAA Vector Select
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-- 0x1 AAAAAAAA Vector Argument LB
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-- 0x2 AAAAAAAA Vector Argument UB
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--
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-- Revision History
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-- Author Date Change
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------------------ -------- ---------------------------------------------------
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-- Seth Henry 04/15/20 Created from o8_epoch_timer due to requirement
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-- change.
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-- Seth Henry 04/16/20 Modified to make use of Open8 bus record
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-- Seth Henry 05/06/20 Modified to eliminate request line and detect idle
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-- conditions instead
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library ieee;
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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_arith.all;
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use ieee.std_logic_misc.all;
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library work;
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use work.Open8_pkg.all;
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entity o8_vector_rx is
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generic(
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Bit_Rate : real;
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Enable_Parity : boolean;
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Parity_Odd_Even_n : std_logic;
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Clock_Frequency : real;
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Address : ADDRESS_TYPE
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);
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port(
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Open8_Bus : in OPEN8_BUS_TYPE;
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Rd_Data : out DATA_TYPE;
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Interrupt : out std_logic;
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--
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Rx_In : in std_logic
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);
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end entity;
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architecture behave of o8_vector_rx is
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alias Clock is Open8_Bus.Clock;
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alias Reset is Open8_Bus.Reset;
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constant User_Addr : std_logic_vector(15 downto 2) :=
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Address(15 downto 2);
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alias Comp_Addr is Open8_Bus.Address(15 downto 2);
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signal Addr_Match : std_logic := '0';
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alias Reg_Sel_d is Open8_Bus.Address(1 downto 0);
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signal Reg_Sel_q : std_logic_vector(1 downto 0) := "00";
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signal Rd_En_d : std_logic := '0';
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signal Rd_En_q : std_logic := '0';
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jshamlet |
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constant BAUD_RATE_DIV : integer := integer(Clock_Frequency / Bit_Rate);
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-- Period of each bit in sub-clocks (subtract one to account for zero)
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constant Full_Per_i : integer := BAUD_RATE_DIV - 1;
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constant Baud_Bits : integer := ceil_log2(Full_Per_i);
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constant FULL_PERIOD : std_logic_vector(Baud_Bits - 1 downto 0) :=
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conv_std_logic_vector(Full_Per_i, Baud_Bits);
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signal Rx_Baud_Cntr : std_logic_vector(Baud_Bits - 1 downto 0) :=
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(others => '0');
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signal Rx_Baud_Tick : std_logic;
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signal Rx_In_SR : std_logic_vector(2 downto 0);
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alias Rx_In_MS is Rx_In_SR(2);
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signal Rx_Idle_Cntr : std_logic_vector(3 downto 0);
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signal RX_Idle : std_logic;
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type VECTOR_RX_STATES is ( GET_VECTOR_CMD, GET_VECTOR_ARG_LB, GET_VECTOR_ARG_UB,
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SEND_INTERRUPT );
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signal Vector_State : VECTOR_RX_STATES := GET_VECTOR_CMD;
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signal Vector_Cmd : DATA_TYPE := x"00";
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signal Vector_Arg_LB : DATA_TYPE := x"00";
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signal Vector_Arg_UB : DATA_TYPE := x"00";
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signal Rx_Data : DATA_TYPE := x"00";
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signal Rx_Valid : std_logic;
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begin
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Addr_Match <= '1' when Comp_Addr = User_Addr else '0';
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Rd_En_d <= Addr_Match and Open8_Bus.Rd_En;
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jshamlet |
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io_reg: process( Clock, Reset )
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begin
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if( Reset = Reset_Level )then
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Reg_Sel_q <= (others => '0');
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Rd_En_q <= '0';
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Rd_Data <= OPEN8_NULLBUS;
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elsif( rising_edge( Clock ) )then
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Reg_Sel_q <= Reg_Sel_d;
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Rd_Data <= OPEN8_NULLBUS;
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Rd_En_q <= Rd_En_d;
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if( Rd_En_q = '1' )then
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case( Reg_Sel_q )is
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when "00" =>
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Rd_Data <= Vector_Cmd;
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when "01" =>
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Rd_Data <= Vector_Arg_LB;
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when "10" =>
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Rd_Data <= Vector_Arg_UB;
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when others =>
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null;
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end case;
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end if;
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end if;
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end process;
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RX_Idle_proc: process( Clock, Reset )
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begin
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if( Reset = Reset_Level )then
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Rx_Baud_Cntr <= (others => '0');
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Rx_Baud_Tick <= '0';
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Rx_In_SR <= (others => '1');
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Rx_Idle_Cntr <= (others => '0');
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Rx_Idle <= '0';
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elsif( rising_edge(Clock) )then
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Rx_Baud_Cntr <= Rx_Baud_Cntr - 1;
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Rx_Baud_Tick <= '0';
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if( Rx_Baud_Cntr = 0 )then
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Rx_Baud_Cntr <= FULL_PERIOD;
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Rx_Baud_Tick <= '1';
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end if;
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Rx_In_SR <= Rx_In_SR(1 downto 0) & Rx_In;
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Rx_Idle_Cntr <= Rx_Idle_Cntr - Rx_Baud_Tick;
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if( Rx_In_MS = '0' )then
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Rx_Idle_Cntr <= (others => '1');
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elsif( Rx_Idle_Cntr = 0 )then
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Rx_Idle_Cntr <= (others => '0');
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end if;
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Rx_Idle <= nor_reduce(Rx_Idle_Cntr);
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end if;
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end process;
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U_RX : entity work.async_ser_rx
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generic map(
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Reset_Level => Reset_Level,
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Enable_Parity => Enable_Parity,
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Parity_Odd_Even_n => Parity_Odd_Even_n,
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Clock_Divider => BAUD_RATE_DIV
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)
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port map(
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Clock => Clock,
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Reset => Reset,
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--
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Rx_In => RX_In,
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--
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Rx_Data => RX_Data,
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Rx_Valid => RX_Valid,
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Rx_PErr => open
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);
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Vector_RX_proc: process( Clock, Reset )
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begin
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if( Reset = Reset_Level )then
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Vector_State <= GET_VECTOR_CMD;
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Vector_Cmd <= x"00";
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Vector_Arg_LB <= x"00";
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Vector_Arg_UB <= x"00";
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Interrupt <= '0';
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elsif( rising_edge(Clock) )then
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Interrupt <= '0';
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case( Vector_State )is
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when GET_VECTOR_CMD =>
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if( Rx_Valid = '1' )then
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Vector_Cmd <= Rx_Data;
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Vector_State <= GET_VECTOR_ARG_LB;
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end if;
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when GET_VECTOR_ARG_LB =>
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if( Rx_Valid = '1' )then
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Vector_Arg_LB <= Rx_Data;
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Vector_State <= GET_VECTOR_ARG_UB;
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end if;
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when GET_VECTOR_ARG_UB =>
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if( Rx_Valid = '1' )then
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Vector_Arg_UB <= Rx_Data;
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Vector_State <= SEND_INTERRUPT;
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end if;
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when SEND_INTERRUPT =>
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Interrupt <= '1';
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Vector_State <= GET_VECTOR_CMD;
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when others => null;
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end case;
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if( Rx_Idle = '1' )then
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Vector_State <= GET_VECTOR_CMD;
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end if;
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end if;
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end process;
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end architecture;
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