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hiroshi |
/* *****************************************************************************
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* title: uart_16550_rll module *
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* description: RS232 Protocol 16550D uart (mostly supported) *
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* languages: systemVerilog *
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* *
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* Copyright (C) 2010 miyagi.hiroshi *
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* *
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* This library is free software; you can redistribute it and/or *
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* modify it under the terms of the GNU Lesser General Public *
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* License as published by the Free Software Foundation; either *
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* version 2.1 of the License, or (at your option) any later version. *
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* *
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* This library is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
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* Lesser General Public License for more details. *
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* *
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* You should have received a copy of the GNU Lesser General Public *
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* License along with this library; if not, write to the Free Software *
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111*1307 USA *
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* *
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* *** GNU LESSER GENERAL PUBLIC LICENSE *** *
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* from http://www.gnu.org/licenses/lgpl.txt *
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*****************************************************************************
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* redleaflogic,ltd *
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* miyagi.hiroshi@redleaflogic.biz *
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* $Id: uart_noize_shaver.sv 108 2010-03-30 02:56:26Z hiroshi $ *
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***************************************************************************** */
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`ifdef SYN
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/* empty */
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`else
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timeunit 1ps ;
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timeprecision 1ps ;
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`endif
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module uart_noize_shaver
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(
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input wire clk_i,
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input wire nrst_i,
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input wire rxd_i,
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output rxd_clean
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) ;
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// -- receiver baud --
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logic [3:0] count ;
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logic [3:0] shift ;
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always_ff @(posedge clk_i, negedge nrst_i) begin
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if(nrst_i == 1'b0)
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count <= #1 0 ;
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else
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count <= #1 count + 4'h1 ;
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end
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always_ff @(posedge clk_i, negedge nrst_i) begin
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if(nrst_i == 1'b0)
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shift <= #1 4'b1111 ;
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else if(count == 4'h0)
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shift <= #1 {shift[2:0], rxd_i} ;
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else
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shift <= #1 shift ;
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end
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assign rxd_clean = shift == 4'hf ||
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shift == 4'he ||
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shift == 4'hd ||
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shift == 4'hb ||
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shift == 4'h7 ;
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endmodule
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