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[/] [can/] [tags/] [rel_10/] [rtl/] [verilog/] [can_btl.v] - Rev 6
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////////////////////////////////////////////////////////////////////// //// //// //// can_btl.v //// //// //// //// //// //// This file is part of the CAN Protocal Controller //// //// http://www.opencores.org/projects/can/ //// //// //// //// //// //// Author(s): //// //// Igor Mohor //// //// igorm@opencores.org //// //// //// //// //// //// All additional information is avaliable in the README.txt //// //// file. //// //// //// ////////////////////////////////////////////////////////////////////// //// //// //// Copyright (C) 2002 Authors //// //// //// //// This source file may be used and distributed without //// //// restriction provided that this copyright statement is not //// //// removed from the file and that any derivative work contains //// //// the original copyright notice and the associated disclaimer. //// //// //// //// This source file is free software; you can redistribute it //// //// and/or modify it under the terms of the GNU Lesser General //// //// Public License as published by the Free Software Foundation; //// //// either version 2.1 of the License, or (at your option) any //// //// later version. //// //// //// //// This source 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 Lesser General Public License for more //// //// details. //// //// //// //// You should have received a copy of the GNU Lesser General //// //// Public License along with this source; if not, download it //// //// from http://www.opencores.org/lgpl.shtml //// //// //// ////////////////////////////////////////////////////////////////////// // // CVS Revision History // // $Log: not supported by cvs2svn $ // Revision 1.2 2002/12/25 14:17:00 mohor // Synchronization working. // // Revision 1.1.1.1 2002/12/20 16:39:21 mohor // Initial // // // // synopsys translate_off `include "timescale.v" // synopsys translate_on `include "can_defines.v" module can_btl ( clk, rst, rx, /* Mode register */ reset_mode, // Not used !!! /* Bus Timing 0 register */ baud_r_presc, sync_jump_width, /* Bus Timing 1 register */ time_segment1, time_segment2, triple_sampling, /* Output signals from this module */ take_sample, clk_en, /* States */ idle, /* bit stream processor (can_bsp.v) */ sync_mode ); parameter Tp = 1; input clk; input rst; input rx; /* Mode register */ input reset_mode; /* Bus Timing 0 register */ input [5:0] baud_r_presc; input [1:0] sync_jump_width; /* Bus Timing 1 register */ input [3:0] time_segment1; input [2:0] time_segment2; input triple_sampling; /* Output signals from this module */ output take_sample; output clk_en; input idle; /* bit stream processor (can_bsp.v) */ input sync_mode; // NOT USED, YET reg [8:0] clk_cnt; reg clk_en; reg sync_blocked; reg sampled_bit; reg [7:0] quant_cnt; reg [3:0] delay; reg sync; reg seg1; reg seg2; reg resync_latched; reg sample_pulse; wire go_sync; wire go_seg1; wire go_seg2; wire [8:0] preset_cnt; wire hard_sync; wire resync; wire sync_window; assign preset_cnt = (baud_r_presc + 1'b1)<<1; // (BRP+1)*2 assign hard_sync = idle & (~rx) & sampled_bit & (~sync_blocked); // Hard synchronization assign resync = (~idle) & (~rx) & sampled_bit & (~sync_blocked); // Re-synchronization /* Generating general enable signal that defines baud rate. */ always @ (posedge clk or posedge rst) begin if (rst) begin clk_cnt <= 0; clk_en <= 1'b0; end else if (clk_cnt == (preset_cnt-1)) begin clk_cnt <=#Tp 0; clk_en <=#Tp 1'b1; end else begin clk_cnt <=#Tp clk_cnt + 1; clk_en <=#Tp 1'b0; end end /* Changing states */ assign go_sync = clk_en & (seg2 & (~resync) & ((quant_cnt == time_segment2))); assign go_seg1 = clk_en & (sync | hard_sync | (resync & seg2 & sync_window) | (resync_latched & sync_window)); assign go_seg2 = clk_en & (seg1 & (quant_cnt == (time_segment1 + delay))); /* When early edge is detected outside of the SJW field, synchronization request is latched and performed when SJW is reached */ always @ (posedge clk or posedge rst) begin if (rst) resync_latched <= 1'b0; else if (resync & seg2 & (~sync_window)) resync_latched <=#Tp 1'b1; else if (go_seg1) resync_latched <= 1'b0; end /* Synchronization stage/segment */ always @ (posedge clk or posedge rst) begin if (rst) sync <= 1; else if (go_sync) sync <=#Tp 1'b1; else if (go_seg1) sync <=#Tp 1'b0; end /* Seg1 stage/segment (together with propagation segment which is 1 quant long) */ always @ (posedge clk or posedge rst) begin if (rst) seg1 <= 0; else if (go_seg1) seg1 <=#Tp 1'b1; else if (go_seg2) seg1 <=#Tp 1'b0; end /* Seg2 stage/segment */ always @ (posedge clk or posedge rst) begin if (rst) seg2 <= 0; else if (go_seg2) seg2 <=#Tp 1'b1; else if (go_sync | go_seg1) seg2 <=#Tp 1'b0; end /* Quant counter */ always @ (posedge clk or posedge rst) begin if (rst) quant_cnt <= 0; else if (go_sync || go_seg1 || go_seg2) quant_cnt <=#Tp 0; else if (clk_en) quant_cnt <=#Tp quant_cnt + 1'b1; end /* When late edge is detected (in seg1 stage), stage seg1 is prolonged. */ always @ (posedge clk or posedge rst) begin if (rst) delay <= 0; else if (clk_en & resync & seg1) delay <=#Tp (quant_cnt > sync_jump_width)? (sync_jump_width + 1) : (quant_cnt + 1); else if (go_sync | go_seg1) delay <=#Tp 0; end // If early edge appears within this window (in seg2 stage), phase error is fully compensated assign sync_window = ((time_segment2 - quant_cnt) < ( sync_jump_width + 1)); // Sampling data always @ (posedge clk or posedge rst) begin if (rst) begin sampled_bit <= 1; sample_pulse <= 0; end else if (go_seg2) begin sampled_bit <=#Tp rx; sample_pulse <=#Tp 1; end else sample_pulse <=#Tp 0; // Sample pulse is for development purposes only. REMOVE ME. end /* Blocking synchronization (can occur only once in a bit time) */ always @ (posedge clk or posedge rst) begin if (rst) sync_blocked <=#Tp 1'b0; else if (clk_en) begin if (hard_sync || resync) sync_blocked <=#Tp 1'b1; else if (seg2 & quant_cnt == time_segment2) sync_blocked <=#Tp 1'b0; end end endmodule
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