pluto_hdl_adi/projects/fmcomms8/common/fmcomms8_spi.v

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2019-10-31 14:56:21 +00:00
// ***************************************************************************
// ***************************************************************************
// Copyright 2014 - 2019 (c) Analog Devices, Inc. All rights reserved.
//
// In this HDL repository, there are many different and unique modules, consisting
// of various HDL (Verilog or VHDL) components. The individual modules are
// developed independently, and may be accompanied by separate and unique license
// terms.
//
// The user should read each of these license terms, and understand the
// freedoms and responsibilities that he or she has by using this source/core.
//
// This core is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE.
//
// Redistribution and use of source or resulting binaries, with or without modification
// of this file, are permitted under one of the following two license terms:
//
// 1. The GNU General Public License version 2 as published by the
// Free Software Foundation, which can be found in the top level directory
// of this repository (LICENSE_GPL2), and also online at:
// <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
//
// OR
//
// 2. An ADI specific BSD license, which can be found in the top level directory
// of this repository (LICENSE_ADIBSD), and also on-line at:
// https://github.com/analogdevicesinc/hdl/blob/master/LICENSE_ADIBSD
// This will allow to generate bit files and not release the source code,
// as long as it attaches to an ADI device.
//
// ***************************************************************************
// ***************************************************************************
`timescale 1ns/100ps
module fmcomms8_spi (
input [ 7:0] spi_csn,
input spi_clk,
input spi_mosi,
input spi_miso_i,
output spi_miso_o,
inout spi_sdio);
// 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;
wire spi_miso_io;
// check on rising edge and change on falling edge
assign spi_csn_s = & spi_csn;
assign spi_enable_s = spi_enable & (~spi_csn[2]);
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 < 6'h3f) ? spi_count + 1'b1 : spi_count;
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 buffer
ad_iobuf #(.DATA_WIDTH(1)) i_iobuf_sdio (
.dio_t (spi_enable_s),
.dio_i (spi_mosi),
.dio_o (spi_miso_io),
.dio_p (spi_sdio));
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assign spi_miso_o = spi_enable_s ? spi_miso_io : spi_miso_i;
endmodule
// ***************************************************************************
// ***************************************************************************