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mohor |
//////////////////////////////////////////////////////////////////////
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//// ////
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//// uart_receiver.v ////
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//// ////
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//// ////
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//// This file is part of the "UART 16550 compatible" project ////
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//// http://www.opencores.org/cores/uart16550/ ////
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//// ////
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//// Documentation related to this project: ////
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//// - http://www.opencores.org/cores/uart16550/ ////
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//// ////
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//// Projects compatibility: ////
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//// - WISHBONE ////
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//// RS232 Protocol ////
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//// 16550D uart (mostly supported) ////
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//// ////
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//// Overview (main Features): ////
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//// UART core receiver logic ////
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//// ////
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//// Known problems (limits): ////
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//// None known ////
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//// ////
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//// To Do: ////
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//// Thourough testing. ////
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//// ////
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//// Author(s): ////
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//// - gorban@opencores.org ////
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//// - Jacob Gorban ////
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mohor |
//// - Igor Mohor (igorm@opencores.org) ////
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27 |
mohor |
//// ////
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//// Created: 2001/05/12 ////
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//// Last Updated: 2001/05/17 ////
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//// (See log for the revision history) ////
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//// ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//// ////
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mohor |
//// Copyright (C) 2000, 2001 Authors ////
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mohor |
//// ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer. ////
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//// ////
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//// This source file is free software; you can redistribute it ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// later version. ////
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//// ////
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//// This source is distributed in the hope that it will be ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// details. ////
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//// ////
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//// You should have received a copy of the GNU Lesser General ////
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//// Public License along with this source; if not, download it ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//
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// CVS Revision History
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//
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// $Log: not supported by cvs2svn $
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47 |
gorban |
// Revision 1.16 2001/11/27 22:17:09 gorban
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// Fixed bug that prevented synthesis in uart_receiver.v
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//
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gorban |
// Revision 1.15 2001/11/26 21:38:54 gorban
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// Lots of fixes:
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// Break condition wasn't handled correctly at all.
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// LSR bits could lose their values.
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// LSR value after reset was wrong.
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// Timing of THRE interrupt signal corrected.
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// LSR bit 0 timing corrected.
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//
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gorban |
// Revision 1.14 2001/11/10 12:43:21 gorban
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// Synthesis bugs fixed. Some other minor changes
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//
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gorban |
// Revision 1.13 2001/11/08 14:54:23 mohor
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// Comments in Slovene language deleted, few small fixes for better work of
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// old tools. IRQs need to be fix.
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//
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mohor |
// Revision 1.12 2001/11/07 17:51:52 gorban
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// Heavily rewritten interrupt and LSR subsystems.
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// Many bugs hopefully squashed.
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//
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gorban |
// Revision 1.11 2001/10/31 15:19:22 gorban
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// Fixes to break and timeout conditions
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//
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gorban |
// Revision 1.10 2001/10/20 09:58:40 gorban
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// Small synopsis fixes
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//
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gorban |
// Revision 1.9 2001/08/24 21:01:12 mohor
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// Things connected to parity changed.
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// Clock devider changed.
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//
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mohor |
// Revision 1.8 2001/08/23 16:05:05 mohor
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// Stop bit bug fixed.
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// Parity bug fixed.
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// WISHBONE read cycle bug fixed,
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// OE indicator (Overrun Error) bug fixed.
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// PE indicator (Parity Error) bug fixed.
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// Register read bug fixed.
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//
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27 |
mohor |
// Revision 1.6 2001/06/23 11:21:48 gorban
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// DL made 16-bit long. Fixed transmission/reception bugs.
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//
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// Revision 1.5 2001/06/02 14:28:14 gorban
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// Fixed receiver and transmitter. Major bug fixed.
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//
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// Revision 1.4 2001/05/31 20:08:01 gorban
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// FIFO changes and other corrections.
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//
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// Revision 1.3 2001/05/27 17:37:49 gorban
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// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.
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//
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// Revision 1.2 2001/05/21 19:12:02 gorban
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// Corrected some Linter messages.
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//
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// Revision 1.1 2001/05/17 18:34:18 gorban
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// First 'stable' release. Should be sythesizable now. Also added new header.
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//
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// Revision 1.0 2001-05-17 21:27:11+02 jacob
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// Initial revision
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//
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//
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33 |
gorban |
// synopsys translate_off
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27 |
mohor |
`include "timescale.v"
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gorban |
// synopsys translate_on
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27 |
mohor |
`include "uart_defines.v"
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module uart_receiver (clk, wb_rst_i, lcr, rf_pop, srx_pad_i, enable, rda_int,
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gorban |
counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask);
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mohor |
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input clk;
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input wb_rst_i;
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mohor |
input [7:0] lcr;
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27 |
mohor |
input rf_pop;
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input srx_pad_i;
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input enable;
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input rda_int;
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input rx_reset;
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gorban |
input lsr_mask;
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mohor |
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gorban |
output [9:0] counter_t;
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mohor |
output [`UART_FIFO_COUNTER_W-1:0] rf_count;
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output [`UART_FIFO_REC_WIDTH-1:0] rf_data_out;
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output rf_overrun;
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output rf_error_bit;
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reg [3:0] rstate;
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reg [3:0] rcounter16;
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reg [2:0] rbit_counter;
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reg [7:0] rshift; // receiver shift register
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reg rparity; // received parity
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reg rparity_error;
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reg rframing_error; // framing error flag
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reg rbit_in;
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reg rparity_xor;
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gorban |
reg [7:0] counter_b; // counts the 0 (low) signals
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27 |
mohor |
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// RX FIFO signals
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reg [`UART_FIFO_REC_WIDTH-1:0] rf_data_in;
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wire [`UART_FIFO_REC_WIDTH-1:0] rf_data_out;
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reg rf_push;
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wire rf_pop;
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wire rf_underrun;
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wire rf_overrun;
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wire [`UART_FIFO_COUNTER_W-1:0] rf_count;
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wire rf_error_bit; // an error (parity or framing) is inside the fifo
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gorban |
wire break_error = (counter_b == 0);
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mohor |
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// RX FIFO instance
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uart_fifo #(`UART_FIFO_REC_WIDTH) fifo_rx(
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.clk( clk ),
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.wb_rst_i( wb_rst_i ),
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.data_in( rf_data_in ),
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.data_out( rf_data_out ),
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.push( rf_push ),
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.pop( rf_pop ),
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.underrun( rf_underrun ),
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.overrun( rf_overrun ),
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.count( rf_count ),
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.error_bit( rf_error_bit ),
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.fifo_reset( rx_reset ),
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gorban |
.reset_status(lsr_mask)
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mohor |
);
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wire rcounter16_eq_7 = (rcounter16 == 4'd7);
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wire rcounter16_eq_0 = (rcounter16 == 4'd0);
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wire rcounter16_eq_1 = (rcounter16 == 4'd1);
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mohor |
wire [3:0] rcounter16_minus_1 = rcounter16 - 1'b1;
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mohor |
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parameter sr_idle = 4'd0;
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parameter sr_rec_start = 4'd1;
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parameter sr_rec_bit = 4'd2;
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parameter sr_rec_parity = 4'd3;
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parameter sr_rec_stop = 4'd4;
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parameter sr_check_parity = 4'd5;
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parameter sr_rec_prepare = 4'd6;
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parameter sr_end_bit = 4'd7;
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parameter sr_ca_lc_parity = 4'd8;
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parameter sr_wait1 = 4'd9;
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parameter sr_push = 4'd10;
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parameter sr_last = 4'd11;
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always @(posedge clk or posedge wb_rst_i)
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begin
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if (wb_rst_i)
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begin
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rstate <= #1 sr_idle;
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rbit_in <= #1 1'b0;
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rcounter16 <= #1 0;
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rbit_counter <= #1 0;
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rparity_xor <= #1 1'b0;
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rframing_error <= #1 1'b0;
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rparity_error <= #1 1'b0;
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rparity <= #1 1'b0;
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rshift <= #1 0;
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rf_push <= #1 1'b0;
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rf_data_in <= #1 0;
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end
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else
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gorban |
if (break_error && rstate != sr_idle) // break condition met while receiver is not idle
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begin
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rstate <= #1 sr_idle;
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rf_data_in <= #1 {8'b0, 3'b100}; // break input (empty character) to receiver FIFO
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rf_push <= #1 1'b1;
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end
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gorban |
else
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mohor |
if (enable)
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begin
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case (rstate)
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gorban |
sr_idle : begin
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rf_push <= #1 1'b0;
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rf_data_in <= #1 0;
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if (srx_pad_i==1'b0) // detected a pulse (start bit?)
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mohor |
begin
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| 243 |
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gorban |
rstate <= #1 sr_rec_start;
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rcounter16 <= #1 4'b1110;
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mohor |
end
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45 |
gorban |
end
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mohor |
sr_rec_start : begin
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if (rcounter16_eq_7) // check the pulse
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if (srx_pad_i==1'b1) // no start bit
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rstate <= #1 sr_idle;
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else // start bit detected
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rstate <= #1 sr_rec_prepare;
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rcounter16 <= #1 rcounter16_minus_1;
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end
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sr_rec_prepare:begin
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case (lcr[/*`UART_LC_BITS*/1:0]) // number of bits in a word
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2'b00 : rbit_counter <= #1 3'b100;
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2'b01 : rbit_counter <= #1 3'b101;
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2'b10 : rbit_counter <= #1 3'b110;
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2'b11 : rbit_counter <= #1 3'b111;
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endcase
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if (rcounter16_eq_0)
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| 263 |
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begin
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| 264 |
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rstate <= #1 sr_rec_bit;
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rcounter16 <= #1 4'b1110;
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rshift <= #1 0;
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end
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| 268 |
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else
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| 269 |
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rstate <= #1 sr_rec_prepare;
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| 270 |
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rcounter16 <= #1 rcounter16_minus_1;
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| 271 |
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end
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| 272 |
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sr_rec_bit : begin
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if (rcounter16_eq_0)
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rstate <= #1 sr_end_bit;
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| 275 |
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if (rcounter16_eq_7) // read the bit
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| 276 |
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case (lcr[/*`UART_LC_BITS*/1:0]) // number of bits in a word
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2'b00 : rshift[4:0] <= #1 {srx_pad_i, rshift[4:1]};
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| 278 |
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2'b01 : rshift[5:0] <= #1 {srx_pad_i, rshift[5:1]};
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| 279 |
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2'b10 : rshift[6:0] <= #1 {srx_pad_i, rshift[6:1]};
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2'b11 : rshift[7:0] <= #1 {srx_pad_i, rshift[7:1]};
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| 281 |
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endcase
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| 282 |
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rcounter16 <= #1 rcounter16_minus_1;
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| 283 |
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end
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| 284 |
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sr_end_bit : begin
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| 285 |
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if (rbit_counter==3'b0) // no more bits in word
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| 286 |
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if (lcr[`UART_LC_PE]) // choose state based on parity
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| 287 |
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rstate <= #1 sr_rec_parity;
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| 288 |
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else
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| 289 |
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begin
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| 290 |
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rstate <= #1 sr_rec_stop;
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| 291 |
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rparity_error <= #1 1'b0; // no parity - no error :)
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| 292 |
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end
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| 293 |
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else // else we have more bits to read
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| 294 |
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begin
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| 295 |
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rstate <= #1 sr_rec_bit;
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| 296 |
39 |
mohor |
rbit_counter <= #1 rbit_counter - 1'b1;
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| 297 |
27 |
mohor |
end
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| 298 |
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rcounter16 <= #1 4'b1110;
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| 299 |
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end
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| 300 |
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sr_rec_parity: begin
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| 301 |
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if (rcounter16_eq_7) // read the parity
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| 302 |
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begin
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| 303 |
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rparity <= #1 srx_pad_i;
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| 304 |
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rstate <= #1 sr_ca_lc_parity;
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| 305 |
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end
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| 306 |
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rcounter16 <= #1 rcounter16_minus_1;
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| 307 |
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end
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| 308 |
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sr_ca_lc_parity : begin // rcounter equals 6
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| 309 |
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rcounter16 <= #1 rcounter16_minus_1;
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| 310 |
37 |
gorban |
rparity_xor <= #1 ^{rshift,rparity}; // calculate parity on all incoming data
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| 311 |
27 |
mohor |
rstate <= #1 sr_check_parity;
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| 312 |
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end
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| 313 |
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sr_check_parity: begin // rcounter equals 5
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| 314 |
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|
case ({lcr[`UART_LC_EP],lcr[`UART_LC_SP]})
|
| 315 |
37 |
gorban |
2'b00: rparity_error <= #1 rparity_xor == 0; // no error if parity 1
|
| 316 |
|
|
2'b01: rparity_error <= #1 ~rparity; // parity should sticked to 1
|
| 317 |
|
|
2'b10: rparity_error <= #1 rparity_xor == 1; // error if parity is odd
|
| 318 |
|
|
2'b11: rparity_error <= #1 rparity; // parity should be sticked to 0
|
| 319 |
27 |
mohor |
endcase
|
| 320 |
|
|
rcounter16 <= #1 rcounter16_minus_1;
|
| 321 |
|
|
rstate <= #1 sr_wait1;
|
| 322 |
|
|
end
|
| 323 |
|
|
sr_wait1 : if (rcounter16_eq_0)
|
| 324 |
|
|
begin
|
| 325 |
|
|
rstate <= #1 sr_rec_stop;
|
| 326 |
|
|
rcounter16 <= #1 4'b1110;
|
| 327 |
|
|
end
|
| 328 |
|
|
else
|
| 329 |
|
|
rcounter16 <= #1 rcounter16_minus_1;
|
| 330 |
|
|
sr_rec_stop : begin
|
| 331 |
|
|
if (rcounter16_eq_7) // read the parity
|
| 332 |
|
|
begin
|
| 333 |
|
|
rframing_error <= #1 !srx_pad_i; // no framing error if input is 1 (stop bit)
|
| 334 |
|
|
rstate <= #1 sr_push;
|
| 335 |
|
|
end
|
| 336 |
|
|
rcounter16 <= #1 rcounter16_minus_1;
|
| 337 |
|
|
end
|
| 338 |
|
|
sr_push : begin
|
| 339 |
|
|
///////////////////////////////////////
|
| 340 |
|
|
// $display($time, ": received: %b", rf_data_in);
|
| 341 |
45 |
gorban |
rf_data_in <= #1 {rshift, 1'b0, rparity_error, rframing_error};
|
| 342 |
27 |
mohor |
rf_push <= #1 1'b1;
|
| 343 |
|
|
rstate <= #1 sr_last;
|
| 344 |
|
|
end
|
| 345 |
|
|
sr_last : begin
|
| 346 |
|
|
if (rcounter16_eq_1)
|
| 347 |
|
|
rstate <= #1 sr_idle;
|
| 348 |
|
|
rcounter16 <= #1 rcounter16_minus_1;
|
| 349 |
|
|
rf_push <= #1 1'b0;
|
| 350 |
|
|
end
|
| 351 |
|
|
default : rstate <= #1 sr_idle;
|
| 352 |
|
|
endcase
|
| 353 |
|
|
end // if (enable)
|
| 354 |
|
|
end // always of receiver
|
| 355 |
|
|
|
| 356 |
|
|
//
|
| 357 |
|
|
// Break condition detection.
|
| 358 |
|
|
// Works in conjuction with the receiver state machine
|
| 359 |
|
|
|
| 360 |
47 |
gorban |
reg [9:0] toc_value; // value to be set to timeout counter
|
| 361 |
|
|
|
| 362 |
|
|
always @(lcr)
|
| 363 |
|
|
case (lcr[3:0])
|
| 364 |
|
|
4'b0000 : toc_value = 447; // 7 bits
|
| 365 |
|
|
4'b0100 : toc_value = 479; // 7.5 bits
|
| 366 |
|
|
4'b0001, 4'b1000 : toc_value = 511; // 8 bits
|
| 367 |
|
|
4'b1100 : toc_value = 543; // 8.5 bits
|
| 368 |
|
|
4'b0010, 4'b0101, 4'b1001 : toc_value = 575; // 9 bits
|
| 369 |
|
|
4'b0011, 4'b0110, 4'b1010, 4'b1101 : toc_value = 639; // 10 bits
|
| 370 |
|
|
4'b0111, 4'b1011, 4'b1110 : toc_value = 703; // 11 bits
|
| 371 |
|
|
4'b1111 : toc_value = 767; // 12 bits
|
| 372 |
|
|
endcase // case(lcr[3:0])
|
| 373 |
|
|
|
| 374 |
|
|
wire [7:0] brc_value; // value to be set to break counter
|
| 375 |
|
|
assign brc_value = toc_value[9:2]; // the same as timeout but 1 insead of 4 character times
|
| 376 |
|
|
|
| 377 |
27 |
mohor |
always @(posedge clk or posedge wb_rst_i)
|
| 378 |
|
|
begin
|
| 379 |
|
|
if (wb_rst_i)
|
| 380 |
47 |
gorban |
counter_b <= #1 8'd159;
|
| 381 |
27 |
mohor |
else
|
| 382 |
39 |
mohor |
if(lsr_mask)
|
| 383 |
47 |
gorban |
counter_b <= #1 brc_value;
|
| 384 |
39 |
mohor |
else
|
| 385 |
27 |
mohor |
if (enable) // only work on enable times
|
| 386 |
39 |
mohor |
if (srx_pad_i)
|
| 387 |
47 |
gorban |
counter_b <= #1 brc_value; // character time length - 1
|
| 388 |
27 |
mohor |
else
|
| 389 |
40 |
gorban |
if (counter_b != 8'b0) // break not reached it
|
| 390 |
|
|
counter_b <= #1 counter_b - 1; // decrement break counter
|
| 391 |
27 |
mohor |
end // always of break condition detection
|
| 392 |
|
|
|
| 393 |
|
|
///
|
| 394 |
|
|
/// Timeout condition detection
|
| 395 |
35 |
gorban |
reg [9:0] counter_t; // counts the timeout condition clocks
|
| 396 |
27 |
mohor |
|
| 397 |
|
|
always @(posedge clk or posedge wb_rst_i)
|
| 398 |
|
|
begin
|
| 399 |
|
|
if (wb_rst_i)
|
| 400 |
47 |
gorban |
counter_t <= #1 10'd639; // 10 bits for the default 8N1
|
| 401 |
27 |
mohor |
else
|
| 402 |
35 |
gorban |
if(rf_push || rf_pop || rda_int || rf_count == 0) // counter is reset when RX FIFO is empty, accessed or above trigger level
|
| 403 |
47 |
gorban |
counter_t <= #1 toc_value;
|
| 404 |
27 |
mohor |
else
|
| 405 |
39 |
mohor |
if (enable && counter_t != 10'b0) // we don't want to underflow
|
| 406 |
|
|
counter_t <= #1 counter_t - 1;
|
| 407 |
27 |
mohor |
end
|
| 408 |
|
|
|
| 409 |
|
|
endmodule
|
