/*******************************************************************************
* Module: simul_clk_mult
* Date:2015-10-10
* Author: Andrey Filippov
* Description: Clock multiplier
*
* Copyright (c) 2015 Elphel, Inc .
* simul_clk_mult.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.
*
* simul_clk_mult.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 .
*
* 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 simul_clk_mult#(
parameter MULTIPLIER = 3,
parameter SKIP_FIRST = 5
) (
input clk_in,
input en,
output clk_out
);
real phase;
real prev_phase = 0.0;
real out_half_period = 0.0;
integer num_period = 0;
reg en1 = 0;
reg clk_out_r = 0;
assign clk_out = (MULTIPLIER == 1)? clk_in: clk_out_r;
always @ (posedge clk_in) begin
phase = $realtime;
if (num_period >= SKIP_FIRST) begin
out_half_period = (phase - prev_phase) / (2 * MULTIPLIER);
en1 = 1;
end
prev_phase = phase;
num_period = num_period + 1;
end
always @ (posedge clk_in) if (en && en1) begin
clk_out_r = 1;
repeat (MULTIPLIER - 1) begin
#out_half_period clk_out_r = 0;
#out_half_period clk_out_r = 1;
end
#out_half_period clk_out_r = 0;
end
endmodule