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//======================================================================
//
// eim_arbiter_cdc.v
// -----------------
// The actual clock domain crossing handler od the EIM arbiter
// for the Cryptech Novena FPGA framework.
//
//
// Author: Pavel Shatov
// Copyright (c) 2014, NORDUnet A/S 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 the NORDUnet nor the names of its contributors may
// be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, 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 eim_arbiter_cdc
(
eim_clk, eim_req, eim_ack, eim_din, eim_dout,
sys_clk, sys_addr,
sys_wren, sys_data_out,
sys_rden, sys_data_in
);
input wire eim_clk; // eim clock
input wire eim_req; // eim transaction request
output wire eim_ack; // eim transaction acknowledge
input wire [50: 0] eim_din; // data from cpu to fpga (write access)
output wire [31: 0] eim_dout; // data from fpga to cpu (read access)
input wire sys_clk; // user internal clock
output wire [16: 0] sys_addr; // user access address
output wire sys_wren; // user write flag
output wire [31: 0] sys_data_out; // user write data
output wire sys_rden; // user read flag
input wire [31: 0] sys_data_in; // user read data
//
// EIM_CLK -> SYS_CLK Request
//
wire sys_req; // request pulse in sys_clk clock domain
wire [50: 0] sys_dout; // transaction data in sys_clk clock domain
cdc_bus_pulse #
(
.DATA_WIDTH (51) // {write, read, msb addr, lsb addr, data}
)
cdc_eim_sys
(
.src_clk (eim_clk),
.src_din (eim_din),
.src_req (eim_req),
.dst_clk (sys_clk),
.dst_dout (sys_dout),
.dst_pulse (sys_req)
);
//
// Output Registers
//
reg sys_wren_reg = 1'b0; //
reg sys_rden_reg = 1'b0; //
reg [16: 0] sys_addr_reg = {17{1'bX}}; //
reg [31: 0] sys_data_out_reg = {32{1'bX}}; //
assign sys_wren = sys_wren_reg;
assign sys_rden = sys_rden_reg;
assign sys_addr = sys_addr_reg;
assign sys_data_out = sys_data_out_reg;
//
// System (User) Clock Access Handler
//
always @(posedge sys_clk)
//
if (sys_req) begin // request detected?
sys_wren_reg <= sys_dout[50]; // set write flag if needed
sys_rden_reg <= sys_dout[49]; // set read flag if needed
sys_addr_reg <= sys_dout[48:32]; // set operation address
sys_data_out_reg <= sys_dout[31: 0]; // set data to write
end else begin // no request active
sys_wren_reg <= 1'b0; // clear write flag
sys_rden_reg <= 1'b0; // clear read flag
end
//
// System Request 2-cycle delay to compensate registered mux delay in user-side logic
//
reg [ 1: 0] sys_req_dly = 2'b00;
always @(posedge sys_clk)
sys_req_dly <= {sys_req_dly[0], sys_req};
//
// SYS_CLK -> EIM_CLK Acknowledge
//
cdc_bus_pulse #
(
.DATA_WIDTH (32) // {data}
)
cdc_sys_eim
(
.src_clk (sys_clk),
.src_din (sys_data_in),
.src_req (sys_req_dly[1]),
.dst_clk (eim_clk),
.dst_dout (eim_dout),
.dst_pulse (eim_ack)
);
endmodule
//======================================================================
// EOF eim_arbiter_cdc.v
//======================================================================
|
