pluto_hdl_adi/projects/daq3/common/daq3_spi.v

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// ***************************************************************************
// ***************************************************************************
// Copyright 2011(c) Analog Devices, Inc.
//
// 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.
// ***************************************************************************
// ***************************************************************************
`timescale 1ns/100ps
module daq3_spi (
spi_csn,
spi_clk,
spi_mosi,
spi_miso,
spi_sdio,
spi_dir);
// 4 wire
input [ 2:0] spi_csn;
input spi_clk;
input spi_mosi;
output spi_miso;
// 3 wire
inout spi_sdio;
output spi_dir;
// internal registers
reg [ 5:0] spi_count = 'd0;
reg spi_rd_wr_n = 'd0;
reg spi_enable = 'd0;
// internal signals
wire spi_csn_s;
wire spi_enable_s;
// check on rising edge and change on falling edge
assign spi_csn_s = & spi_csn;
assign spi_dir = ~spi_enable_s;
assign spi_enable_s = spi_enable & ~spi_csn_s;
always @(posedge spi_clk or posedge spi_csn_s) begin
if (spi_csn_s == 1'b1) begin
spi_count <= 6'd0;
spi_rd_wr_n <= 1'd0;
end else begin
spi_count <= spi_count + 1'b1;
if (spi_count == 6'd0) begin
spi_rd_wr_n <= spi_mosi;
end
end
end
always @(negedge spi_clk or posedge spi_csn_s) begin
if (spi_csn_s == 1'b1) begin
spi_enable <= 1'b0;
end else begin
if (spi_count == 6'd16) begin
spi_enable <= spi_rd_wr_n;
end
end
end
// io butter
IOBUF i_iobuf_sdio (
.T (spi_enable_s),
.I (spi_mosi),
.O (spi_miso),
.IO (spi_sdio));
endmodule
// ***************************************************************************
// ***************************************************************************