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//
// Copyright 2013 Ettus Research LLC
//
// This program 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.
//
// This program 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/>.
//
module timekeeper
#(parameter BASE = 0)
(input clk, input reset, input pps,
input set_stb, input [7:0] set_addr, input [31:0] set_data,
output reg [63:0] vita_time, output reg [63:0] vita_time_lastpps);
//////////////////////////////////////////////////////////////////////////
// timer settings for this module
//////////////////////////////////////////////////////////////////////////
wire [63:0] time_at_next_event;
wire set_time_pps, set_time_now;
wire cmd_trigger;
setting_reg #(.my_addr(BASE), .width()) sr_time_hi
(.clk(clk), .rst(reset), .strobe(set_stb), .addr(set_addr), .in(set_data),
.out(time_at_next_event[63:32]), .changed());
setting_reg #(.my_addr(BASE+1), .width()) sr_time_lo
(.clk(clk), .rst(reset), .strobe(set_stb), .addr(set_addr), .in(set_data),
.out(time_at_next_event[31:0]), .changed());
setting_reg #(.my_addr(BASE+2), .width(2)) sr_ctrl
(.clk(clk), .rst(reset), .strobe(set_stb), .addr(set_addr), .in(set_data),
.out({set_time_pps, set_time_now}), .changed(cmd_trigger));
//////////////////////////////////////////////////////////////////////////
// PPS edge detection logic
//////////////////////////////////////////////////////////////////////////
reg pps_del, pps_del2;
always @(posedge clk)
{pps_del2,pps_del} <= {pps_del, pps};
wire pps_edge = !pps_del2 & pps_del;
//////////////////////////////////////////////////////////////////////////
// track the time at last pps so host can detect the pps
//////////////////////////////////////////////////////////////////////////
always @(posedge clk)
if(pps_edge) vita_time_lastpps <= vita_time;
//////////////////////////////////////////////////////////////////////////
// arm the trigger to latch a new time when the ctrl register is written
//////////////////////////////////////////////////////////////////////////
reg armed;
wire time_event = armed && ((set_time_now) || (set_time_pps && pps_edge));
always @(posedge clk) begin
if (reset) armed <= 1'b0;
else if (cmd_trigger) armed <= 1'b1;
else if (time_event) armed <= 1'b0;
end
//////////////////////////////////////////////////////////////////////////
// vita time tracker - update every tick or when we get an "event"
//////////////////////////////////////////////////////////////////////////
always @(posedge clk)
if(reset)
vita_time <= 64'h0;
else if (time_event)
vita_time <= time_at_next_event;
else
vita_time <= vita_time + 64'h1;
endmodule // timekeeper
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