diff --git a/library/common/ad_sysref_gen.v b/library/common/ad_sysref_gen.v new file mode 100644 index 000000000..0bf970890 --- /dev/null +++ b/library/common/ad_sysref_gen.v @@ -0,0 +1,87 @@ +// *************************************************************************** +// *************************************************************************** +// Copyright 2016(c) Analog Devices, Inc. +// +// 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 Analog Devices, Inc. nor the names of its +// contributors may be used to endorse or promote products derived +// from this software without specific prior written permission. +// - The use of this software may or may not infringe the patent rights +// of one or more patent holders. This license does not release you +// from the requirement that you obtain separate licenses from these +// patent holders to use this software. +// - Use of the software either in source or binary form, must be run +// on or directly connected to an Analog Devices Inc. component. +// +// THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, +// INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A +// PARTICULAR PURPOSE ARE DISCLAIMED. +// +// IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, +// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, INTELLECTUAL PROPERTY +// RIGHTS, 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. +// *************************************************************************** +// *************************************************************************** +// *************************************************************************** +// *************************************************************************** + +`timescale 1ns/100ps + +module ad_sysref_gen ( + + input core_clk, + + input sysref_en, + output reg sysref_out +); + + // SYSREF period is multiple of core_clk, and has a duty cycle of 50% + // NOTE: if SYSREF always on (this is a JESD204 IP configuration), + // the period must be a correct multiple of the multiframe period + parameter SYSREF_PERIOD = 128; + + localparam SYSREF_HALFPERIOD = SYSREF_PERIOD/2 - 1; + + reg [ 7:0] counter; + reg sysref_en_m1; + reg sysref_en_m2; + reg sysref_en_int; + + // bring the enable signal to JESD core clock domain + always @(posedge core_clk) begin + sysref_en_m1 <= sysref_en; + sysref_en_m2 <= sysref_en_m1; + sysref_en_int <= sysref_en_m2; + end + + // free running counter for periodic SYSREF generation + always @(posedge core_clk) begin + if (sysref_en_int) begin + counter <= (counter < SYSREF_HALFPERIOD) ? counter + 1 : 0; + end else begin + counter <= 0; + end + end + + // generate SYSREF + always @(posedge core_clk) begin + if (counter == SYSREF_HALFPERIOD) begin + sysref_out <= ~sysref_out; + end else begin + sysref_out <= 1'b0; + end + end + +endmodule