dly01_var.v 2.46 KB
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/*!
 * <b>Module:</b>dly01_var
 * @file dly01_var.v
 * @date 2014-05-30  
 * @author Andrey Filippov
 *
 * @brief Synchronous delay by 1-2^N clock cycles with reset (will map to primitive)
 *
 * @copyright Copyright (c) 2016 Elphel, Inc.
 *
 * <b>License:</b>
 *
 * dly01_var.v is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 *  dly01_var.v 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.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/> .
 *
 * Additional permission under GNU GPL version 3 section 7:
 * If you modify this Program, or any covered work, by linking or combining it
 * with independent modules provided by the FPGA vendor only (this permission
 * does not extend to any 3-rd party modules, "soft cores" or macros) under
 * different license terms solely for the purpose of generating binary "bitstream"
 * files and/or simulating the code, the copyright holders of this Program give
 * you the right to distribute the covered work without those independent modules
 * as long as the source code for them is available from the FPGA vendor free of
 * charge, and there is no dependence on any encrypted modules for simulating of
 * the combined code. This permission applies to you if the distributed code
 * contains all the components and scripts required to completely simulate it
 * with at least one of the Free Software programs.
 */
`timescale 1ns/1ps

module  dly01_var#(
    parameter WIDTH = 4 
)(
    input             clk,
    input             rst,
    input [WIDTH-1:0] dly,
    input             din,
    output            dout
);
    localparam LENGTH = (1 << WIDTH); 
    reg [LENGTH -1:0] sr=0;
`ifdef SHREG_SEQUENTIAL_RESET
    always @ (posedge clk) begin
        sr <= {sr[LENGTH-2:0], din & ~rst}; 
    end
`else 
//    always @ (posedge rst or posedge clk) begin
    always @ (posedge clk) begin
       if (rst) sr <=0;
       else     sr <= {sr[LENGTH-2:0],din}; 
    end
`endif
`ifdef SIMULATION
    assign dout = (|sr) ? ((&sr) ? 1'b1 : sr[dly]) :  1'b0 ;
`else
    assign dout =sr[dly];
`endif        
endmodule