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// ***************************************************************************
// ***************************************************************************
// Copyright 2013(c) Analog Devices, Inc.
// Author: Lars-Peter Clausen <lars@metafoo.de>
//
// 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.
// ***************************************************************************
// ***************************************************************************
module fifo_address_gray (
input m_axis_aclk,
input m_axis_aresetn,
input m_axis_ready,
output reg m_axis_valid,
output reg [ADDRESS_WIDTH:0] m_axis_level,
input s_axis_aclk,
input s_axis_aresetn,
output reg s_axis_ready,
input s_axis_valid,
output reg s_axis_empty,
output [ADDRESS_WIDTH-1:0] s_axis_waddr,
output reg [ADDRESS_WIDTH:0] s_axis_room
);
parameter ADDRESS_WIDTH = 4;
reg [ADDRESS_WIDTH:0] _s_axis_waddr = 'h00;
reg [ADDRESS_WIDTH:0] _s_axis_waddr_next;
reg [ADDRESS_WIDTH:0] _m_axis_raddr = 'h00;
reg [ADDRESS_WIDTH:0] _m_axis_raddr_next;
reg [ADDRESS_WIDTH:0] s_axis_waddr_gray = 'h00;
wire [ADDRESS_WIDTH:0] s_axis_waddr_gray_next;
wire [ADDRESS_WIDTH:0] s_axis_raddr_gray;
reg [ADDRESS_WIDTH:0] m_axis_raddr_gray = 'h00;
wire [ADDRESS_WIDTH:0] m_axis_raddr_gray_next;
wire [ADDRESS_WIDTH:0] m_axis_waddr_gray;
assign s_axis_waddr = _s_axis_waddr[ADDRESS_WIDTH-1:0];
always @(*)
begin
if (s_axis_ready && s_axis_valid)
_s_axis_waddr_next <= _s_axis_waddr + 1;
else
_s_axis_waddr_next <= _s_axis_waddr;
end
assign s_axis_waddr_gray_next = _s_axis_waddr_next ^ _s_axis_waddr_next[ADDRESS_WIDTH:1];
always @(posedge s_axis_aclk)
begin
if (s_axis_aresetn == 1'b0) begin
_s_axis_waddr <= 'h00;
s_axis_waddr_gray <= 'h00;
end else begin
_s_axis_waddr <= _s_axis_waddr_next;
s_axis_waddr_gray <= s_axis_waddr_gray_next;
end
end
always @(*)
begin
if (m_axis_ready && m_axis_valid)
_m_axis_raddr_next <= _m_axis_raddr + 1;
else
_m_axis_raddr_next <= _m_axis_raddr;
end
assign m_axis_raddr_gray_next = _m_axis_raddr_next ^ _m_axis_raddr_next[ADDRESS_WIDTH:1];
always @(posedge m_axis_aclk)
begin
if (m_axis_aresetn == 1'b0) begin
_m_axis_raddr <= 'h00;
m_axis_raddr_gray <= 'h00;
end else begin
_m_axis_raddr <= _m_axis_raddr_next;
m_axis_raddr_gray <= m_axis_raddr_gray_next;
end
end
sync_bits #(
.NUM_OF_BITS(ADDRESS_WIDTH + 1)
) i_waddr_sync (
.out_clk(m_axis_aclk),
.out_resetn(m_axis_aresetn),
.in(s_axis_waddr_gray),
.out(m_axis_waddr_gray)
);
sync_bits #(
.NUM_OF_BITS(ADDRESS_WIDTH + 1)
) i_raddr_sync (
.out_clk(s_axis_aclk),
.out_resetn(s_axis_aresetn),
.in(m_axis_raddr_gray),
.out(s_axis_raddr_gray)
);
always @(posedge s_axis_aclk)
begin
if (s_axis_aresetn == 1'b0) begin
s_axis_ready <= 1'b1;
s_axis_empty <= 1'b1;
end else begin
s_axis_ready <= (s_axis_raddr_gray[ADDRESS_WIDTH] == s_axis_waddr_gray_next[ADDRESS_WIDTH] ||
s_axis_raddr_gray[ADDRESS_WIDTH-1] == s_axis_waddr_gray_next[ADDRESS_WIDTH-1] ||
s_axis_raddr_gray[ADDRESS_WIDTH-2:0] != s_axis_waddr_gray_next[ADDRESS_WIDTH-2:0]);
s_axis_empty <= s_axis_raddr_gray == s_axis_waddr_gray_next;
end
end
always @(posedge m_axis_aclk)
begin
if (s_axis_aresetn == 1'b0)
m_axis_valid <= 1'b0;
else begin
m_axis_valid <= m_axis_waddr_gray != m_axis_raddr_gray_next;
end
end
endmodule
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