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Diffstat (limited to 'src/rtl/eim_arbiter_cdc.v')
| -rw-r--r-- | src/rtl/eim_arbiter_cdc.v | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/src/rtl/eim_arbiter_cdc.v b/src/rtl/eim_arbiter_cdc.v new file mode 100644 index 0000000..15dc433 --- /dev/null +++ b/src/rtl/eim_arbiter_cdc.v @@ -0,0 +1,143 @@ +//====================================================================== +// +// 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) 2015, 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 + ( + 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) // request detected? + begin + 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 // no request active + begin + 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) + ) + 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 +//====================================================================== |