pluto_hdl_adi/library/axi_i2s_adi/fifo_synchronizer.vhd

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-- ***************************************************************************
-- ***************************************************************************
-- Copyright 2013(c) Analog Devices, Inc.
-- Author: Lars-Peter Clausen <lars-peter.clausen@analog.com>
--
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without modification,
-- are permitted provided that the following conditions are met:
-- - Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
-- - Redistributions in binary form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in
-- the documentation and/or other materials provided with the
-- distribution.
-- - Neither the name of Analog Devices, Inc. nor the names of its
-- contributors may be used to endorse or promote products derived
-- from this software without specific prior written permission.
-- - The use of this software may or may not infringe the patent rights
-- of one or more patent holders. This license does not release you
-- from the requirement that you obtain separate licenses from these
-- patent holders to use this software.
-- - Use of the software either in source or binary form, must be run
-- on or directly connected to an Analog Devices Inc. component.
--
-- THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
-- INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A
-- PARTICULAR PURPOSE ARE DISCLAIMED.
--
-- IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
-- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, INTELLECTUAL PROPERTY
-- RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
-- BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-- STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-- THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-- ***************************************************************************
-- ***************************************************************************
library ieee;
use ieee.std_logic_1164.all;
entity fifo_synchronizer is
generic (
DEPTH : integer := 4;
WIDTH : integer := 2
);
port (
in_clk : in std_logic;
in_resetn : in std_logic;
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in_data : in std_logic_vector(WIDTH - 1 downto 0);
in_tick : in std_logic;
out_clk : in std_logic;
out_resetn : in std_logic;
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out_data : out std_logic_vector(WIDTH - 1 downto 0);
out_tick : out std_logic
);
end fifo_synchronizer;
architecture impl of fifo_synchronizer is
type DATA_SYNC_FIFO_TYPE is array (0 to DEPTH - 1) of std_logic_vector(WIDTH - 1 downto 0);
signal fifo: DATA_SYNC_FIFO_TYPE;
signal rd_addr : natural range 0 to DEPTH - 1;
signal wr_addr : natural range 0 to DEPTH - 1;
signal cdc_sync_stage0_tick : std_logic;
signal cdc_sync_stage1_tick : std_logic;
signal cdc_sync_stage2_tick : std_logic;
signal cdc_sync_stage3_tick : std_logic;
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signal tick : std_logic;
begin
process (in_clk)
begin
if rising_edge(in_clk) then
if in_tick = '1' then
cdc_sync_stage0_tick <= not cdc_sync_stage0_tick;
fifo(wr_addr) <= in_data;
end if;
end if;
end process;
process (in_clk)
begin
if rising_edge(in_clk) then
if in_resetn = '0' then
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wr_addr <= 0;
else
if in_tick = '1' then
wr_addr <= (wr_addr + 1) mod DEPTH;
end if;
end if;
end if;
end process;
process (out_clk)
begin
if rising_edge(out_clk) then
cdc_sync_stage1_tick <= cdc_sync_stage0_tick;
cdc_sync_stage2_tick <= cdc_sync_stage1_tick;
cdc_sync_stage3_tick <= cdc_sync_stage2_tick;
end if;
end process;
tick <= cdc_sync_stage2_tick xor cdc_sync_stage3_tick;
out_tick <= tick;
process (out_clk)
begin
if rising_edge(out_clk) then
if tick = '1' then
out_data <= fifo(rd_addr);
end if;
end if;
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end process;
process (out_clk)
begin
if rising_edge(out_clk) then
if out_resetn = '0' then
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rd_addr <= 0;
else
if tick = '1' then
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rd_addr <= (rd_addr + 1) mod DEPTH;
end if;
end if;
end if;
end process;
end;