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/* *****************************************************************************
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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_receiver.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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import uart_package:: * ;
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module uart_receiver(
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input wire clk_i,
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input wire nrst_i,
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input wire rxd_clean,
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input wire rec_clk_en,
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input wire rec_sample_pulse,
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input wire leading_edge,
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input wire timeout_signal,
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fifo_bus fifo_push,
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input u_reg_t u_reg,
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output codec_state_t next_state,
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output logic rec_buf_empty,
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output logic overrun
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) ;
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// codec_state_t next_state ;
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u_codec_t rec_codec ;
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always @(posedge clk_i, negedge nrst_i) begin
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if(nrst_i == 1'b0)
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rec_codec.line <= #1 1'b1 ;
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else
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rec_codec.line <= #1 rxd_clean ;
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end
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// --- fifo push --
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assign fifo_push.push_dat = {rec_codec.parity_err, // bit[10]
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rec_codec.framing_err, // 9
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rec_codec.break_err, // 8
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rec_codec.data_r} ; // [7:0]
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logic push_dly ;
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always @(posedge clk_i, negedge nrst_i) begin
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if(nrst_i == 1'b0)
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push_dly <= #1 1'b0 ;
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else
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push_dly <= #1 next_state == STOP && rec_sample_pulse == 1'b1 ;
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end
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assign fifo_push.push = push_dly == 1'b1 ;
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// -- trasmitter state logic --
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uart_codec_state rec_state(.u_reg(u_reg),
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.codec(rec_codec),
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.receiver_mode(1'b1),
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.timeout_signal(timeout_signal),
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.next_state(next_state)) ;
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// -- state register --
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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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rec_codec.state <= #1 IDLE ;
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else if(rec_clk_en == 1'b1 || leading_edge == 1'b1)
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rec_codec.state <= #1 next_state ;
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else
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rec_codec.state <= #1 rec_codec.state ;
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end
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// -- line input --
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always_ff @(posedge clk_i, negedge nrst_i) begin
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if(nrst_i == 1'b0) begin
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rec_codec.data_r <= #1 8'h00 ;
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rec_codec.framing_err <= #1 1'b0 ;
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rec_codec.parity_err <= #1 1'b0 ;
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rec_codec.break_err <= #1 1'b0 ;
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overrun <= #1 1'b0 ;
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end
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else begin
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if(rec_sample_pulse == 1'b1)
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case (next_state)
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IDLE : /* empty */ ;
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START : begin
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overrun <= #1 1'b0 ;
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rec_codec.framing_err <= #1 1'b0 ;
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rec_codec.parity_err <= #1 1'b0 ;
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rec_codec.break_err <= #1 1'b0 ;
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end
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SEL_0 : rec_codec.data_r[0] <= #1 rec_codec.line ;
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SEL_1 : rec_codec.data_r[1] <= #1 rec_codec.line ;
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SEL_2 : rec_codec.data_r[2] <= #1 rec_codec.line ;
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SEL_3 : rec_codec.data_r[3] <= #1 rec_codec.line ;
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SEL_4 : rec_codec.data_r[4] <= #1 rec_codec.line ;
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SEL_5 : rec_codec.data_r[5] <= #1 rec_codec.line ;
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SEL_6 : rec_codec.data_r[6] <= #1 rec_codec.line ;
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DATA_END : begin
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if(u_reg.line_control_reg.char_length == CHAR_7_BIT) begin
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rec_codec.data_r[6] <= #1 rec_codec.line ;
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rec_codec.data_r[7] <= #1 1'b0 ;
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end
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else begin
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rec_codec.data_r[7] <= #1 rec_codec.line ;
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end
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overrun <= #1 fifo_push.full ;
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end
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PARITY : begin
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if(u_reg.line_control_reg.even_parity == 1'b1)
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rec_codec.parity_err <= #1 (^rec_codec.data_r) ^ rec_codec.line ;
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else
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rec_codec.parity_err <= #1 ~(^rec_codec.data_r) ^ rec_codec.line ;
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end
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STOP : begin
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rec_codec.framing_err <= #1 rec_codec.line == 1'b0 &&
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rec_codec.data_r[7:0] != 8'h00 ;
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rec_codec.break_err <= #1 rec_codec.data_r[7:0] == 8'h00 &&
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rec_codec.line == 1'b0 &&
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rec_codec.parity_err == 1'b0 ;
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end
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default : /* empty */ ;
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endcase // case (state)
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end // if (sample_en == 1'b1)
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end // always_ff @ (posedge clk, negedge nrst)
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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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rec_buf_empty <= 1'b0 ;
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else if(next_state == IDLE || next_state == STOP)
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rec_buf_empty <= #1 1'b1 ;
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else
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rec_buf_empty <= #1 1'b0 ;
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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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rec_codec.start <= #1 1'b0 ;
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else if(rec_codec.state == START)
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rec_codec.start <= #1 1'b0 ;
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else if(leading_edge == 1'b1)
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rec_codec.start <= #1 1'b1 ;
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else
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rec_codec.start <= #1 rec_codec.start ;
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end
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endmodule
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/// END OF FILE ///
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