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[/] [xulalx25soc/] [trunk/] [rtl/] [rtcdate.v] - Rev 72
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/////////////////////////////////////////////////////////////////////////// // // Filename: rtcdate.v // // Project: A Wishbone Controlled Real--time Clock Core // // Purpose: // This core provides a real-time date function that can be coupled with // a real-time clock. The date provided is in Binary Coded Decimal (bcd) // form, and available for reading and writing over the Wishbone Bus. // // WARNING: Race conditions exist when updating the date across the Wishbone // bus at or near midnight. (This should be obvious, but it bears // stating.) Specifically, if the update command shows up at the same // clock as the ppd clock, then the ppd clock will be ignored and the // new date will be the date of the day following midnight. However, // if the update command shows up one clock before the ppd, then the date // may be updated, but may have problems dealing with the last day of the // month or year. To avoid race conditions, update the date sometime // after the stroke of midnight and before 5 clocks before the next // midnight. If you are concerned that you might hit a race condition, // just read the clock again (5+ clocks later) to make certain you set // it correctly. // // // Creator: Dan Gisselquist, Ph.D. // Gisselquist Technology, LLC // /////////////////////////////////////////////////////////////////////////// // // Copyright (C) 2015, Gisselquist Technology, LLC // // This program is free software (firmware): 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 MERCHANTIBILITY 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. (It's in the $(ROOT)/doc directory. Run make with no // target there if the PDF file isn't present.) If not, see // <http://www.gnu.org/licenses/> for a copy. // // License: GPL, v3, as defined and found on www.gnu.org, // http://www.gnu.org/licenses/gpl.html // // /////////////////////////////////////////////////////////////////////////// module rtcdate(i_clk, i_ppd, i_wb_cyc, i_wb_stb, i_wb_we, i_wb_data, o_wb_ack, o_wb_stall, o_wb_data); input i_clk; // A one part per day signal, i.e. basically a clock enable line that // controls when the beginning of the day happens. This line should // be high on the very last second of any day in order for the rtcdate // module to always have the right date. input i_ppd; // Wishbone inputs input i_wb_cyc, i_wb_stb, i_wb_we; input [31:0] i_wb_data; // Wishbone outputs output reg o_wb_ack; output wire o_wb_stall; output wire [31:0] o_wb_data; reg [5:0] r_day; reg [4:0] r_mon; reg [13:0] r_year; reg last_day_of_month, last_day_of_year, is_leap_year; always @(posedge i_clk) last_day_of_year <= (last_day_of_month) && (r_mon == 5'h12); always @(posedge i_clk) begin case(r_mon) 5'h01: last_day_of_month <= (r_day >= 6'h31); // Jan 5'h02: last_day_of_month <= (r_day >= 6'h29) ||((~is_leap_year)&&(r_day == 6'h28)); 5'h03: last_day_of_month <= (r_day >= 6'h31); // March 5'h04: last_day_of_month <= (r_day >= 6'h30); // April 5'h05: last_day_of_month <= (r_day >= 6'h31); // May 5'h06: last_day_of_month <= (r_day >= 6'h30); // June 5'h07: last_day_of_month <= (r_day >= 6'h31); // July 5'h08: last_day_of_month <= (r_day >= 6'h31); // August 5'h09: last_day_of_month <= (r_day >= 6'h30); // Sept 5'h10: last_day_of_month <= (r_day >= 6'h31); // October 5'h11: last_day_of_month <= (r_day >= 6'h30); // November 5'h12: last_day_of_month <= (r_day >= 6'h31); // December default: last_day_of_month <= 1'b0; endcase end reg year_divisible_by_four, century_year, four_century_year; always @(posedge i_clk) year_divisible_by_four<= ((~r_year[0])&&(r_year[4]==r_year[1])); always @(posedge i_clk) century_year <= (r_year[7:0] == 8'h00); always @(posedge i_clk) four_century_year <= ((~r_year[8])&&((r_year[12]==r_year[9]))); always @(posedge i_clk) is_leap_year <= (year_divisible_by_four)&&((~century_year) ||((century_year)&&(four_century_year))); // Adjust the day of month initial r_day = 6'h01; always @(posedge i_clk) begin if ((r_day == 0)||(r_day > 6'h31)||(r_day[3:0] > 4'h9)) r_day <= 6'h01; else if ((i_ppd)&&(last_day_of_month)) r_day <= 6'h01; else if ((i_ppd)&&(r_day[3:0] != 4'h9)) r_day[3:0] <= r_day[3:0] + 4'h1; else if (i_ppd) begin r_day[3:0] <= 4'h0; r_day[5:4] <= r_day[5:4] + 2'h1; end if ((i_wb_cyc)&&(i_wb_stb)&&(i_wb_we)&&(i_wb_data[7:0]!=8'hff)) r_day <= i_wb_data[5:0]; end // Adjust the month of the year initial r_mon = 5'h01; always @(posedge i_clk) begin if ((r_mon == 0)||(r_mon > 5'h12)||(r_mon[3:0] > 4'h9)) r_mon <= 5'h01; else if ((i_ppd)&&(last_day_of_year)) r_mon <= 5'h01; else if ((i_ppd)&&(last_day_of_month)&&(r_mon[3:0] != 4'h9)) r_mon[3:0] <= r_mon[3:0] + 4'h1; else if ((i_ppd)&&(last_day_of_month)) begin r_mon[3:0] <= 4'h0; r_mon[4] <= 1; end if ((i_wb_cyc)&&(i_wb_stb)&&(i_wb_we)&&(i_wb_data[15:8]!=8'hff)) r_mon <= i_wb_data[12:8]; end // Adjust the year initial r_year = 14'h2000; always @(posedge i_clk) begin // Deal with any out of bounds conditions if (r_year[3:0] > 4'h9) r_year[3:0] <= 4'h0; if (r_year[7:4] > 4'h9) r_year[7:4] <= 4'h0; if (r_year[11:8] > 4'h9) r_year[11:8] <= 4'h0; if ((i_ppd)&&(last_day_of_year)) begin if (r_year[3:0] != 4'h9) r_year[3:0] <= r_year[3:0] + 4'h1; else begin r_year[3:0] <= 4'h0; if (r_year[7:4] != 4'h9) r_year[7:4] <= r_year[7:4] + 4'h1; else begin r_year[7:4] <= 4'h0; if (r_year[11:8] != 4'h9) r_year[11:8] <= r_year[11:8]+4'h1; else begin r_year[11:8] <= 4'h0; r_year[13:12] <= r_year[13:12]+2'h1; end end end end if ((i_wb_cyc)&&(i_wb_stb)&&(i_wb_we)&&(i_wb_data[31:16]!=16'hffff)) r_year <= i_wb_data[29:16]; end always @(posedge i_clk) o_wb_ack <= ((i_wb_cyc)&&(i_wb_stb)); assign o_wb_stall = 1'b0; assign o_wb_data = { 2'h0, r_year, 3'h0, r_mon, 2'h0, r_day }; endmodule
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