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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  OMS 8051 cores UART Interface Module                        ////

////                                                              ////

////  This file is part of the OMS 8051 cores project             ////

////  http://www.opencores.org/cores/oms8051mini/                 ////

////                                                              ////

////  Description                                                 ////

////  OMS 8051 definitions.                                       ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

////  Author(s):                                                  ////

////      - Dinesh Annayya, dinesha@opencores.org                 ////

////                                                              ////

////  Revision :                                                  //// 

////     v-0.0 : NOV 26, 2016                                     ////

////        1. initial version picked from                        ////

////          http://www.opencores.org/cores/turbo8051/           ////

////     v-0.1 : NOV 28, 2016                                     ////

////        2.  Register access correction                        ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// 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                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

module uart_core

     (

        app_reset_n ,

        app_clk ,

        // Reg Bus Interface Signal

        reg_cs,

        reg_wr,

        reg_addr,

        reg_wdata,

        reg_be,

        // Outputs

        reg_rdata,

        reg_ack,

       // Line Interface

        si,

        so

     );

parameter W  = 8'd8;

parameter DP = 8'd16;

parameter AW = (DP == 2)   ? 1 :

               (DP == 4)   ? 2 :

               (DP == 8)   ? 3 :

               (DP == 16)  ? 4 :

               (DP == 32)  ? 5 :

               (DP == 64)  ? 6 :

               (DP == 128) ? 7 :

               (DP == 256) ? 8 : 0;

input        app_reset_n          ; // application reset

input        app_clk              ; // application clock

//---------------------------------

// Reg Bus Interface Signal

//---------------------------------

input             reg_cs         ;

input             reg_wr         ;

input [3:0]       reg_addr       ;

input [31:0]      reg_wdata      ;

input [3:0]       reg_be         ;

// Outputs

output [31:0]     reg_rdata      ;

output            reg_ack     ;

// Line Interface

input         si                  ; // uart si

output        so                  ; // uart so

// Wire Declaration

wire [W-1: 0]   tx_fifo_rd_data;

wire [W-1: 0]   rx_fifo_wr_data;

wire [W-1: 0]   app_rxfifo_data;

wire [W-1: 0]   app_txfifo_data;

wire [1  : 0]   error_ind;

// Wire 

wire         cfg_tx_enable        ; // Tx Enable

wire         cfg_rx_enable        ; // Rx Enable

wire         cfg_stop_bit         ; // 0 -> 1 Stop, 1 -> 2 Stop

wire   [1:0] cfg_pri_mod          ; // priority mode, 0 -> nop, 1 -> Even, 2 -> Odd

wire        frm_error_o          ; // framing error

wire        par_error_o          ; // par error

wire        rx_fifo_full_err_o   ; // rx fifo full error

wire   [11:0] cfg_baud_16x        ; // 16x Baud clock generation

wire        rx_fifo_wr_full      ;

wire        app_rxfifo_empty     ;

uart_cfg u_cfg (

             . mclk          (app_clk),

             . reset_n       (app_reset_n),

        // Reg Bus Interface Signal

             . reg_cs        (reg_cs),

             . reg_wr        (reg_wr),

             . reg_addr      (reg_addr),

             . reg_wdata     (reg_wdata),

             . reg_be        (reg_be),

            // Outputs

            . reg_rdata      (reg_rdata),

            . reg_ack        (reg_ack),

       // configuration

            . cfg_tx_enable       (cfg_tx_enable),

            . cfg_rx_enable       (cfg_rx_enable),

            . cfg_stop_bit        (cfg_stop_bit),

            . cfg_pri_mod         (cfg_pri_mod),

            . cfg_baud_16x        (cfg_baud_16x),

            . tx_fifo_full        (app_tx_fifo_full),

            . tx_fifo_wr_en       (tx_fifo_wr_en),

            . tx_fifo_data        (app_txfifo_data),

            . rx_fifo_empty       (app_rxfifo_empty),

            . rx_fifo_rd_en       (app_rxfifo_rd_en),

            . rx_fifo_data        (app_rxfifo_data) ,

            . frm_error_o         (frm_error_o),

            . par_error_o         (par_error_o),

            . rx_fifo_full_err_o  (rx_fifo_full_err_o)

        );

// 16x Baud clock generation

// Example: to generate 19200 Baud clock from 50Mhz Link clock

//    50 * 1000 * 1000 / (2 + cfg_baud_16x) = 19200 * 16

//    cfg_baud_16x = 0xA0 (160)

wire line_clk_16x;

clk_ctl #(11) u_clk_ctl (

   // Outputs

       .clk_o          (line_clk_16x),

   // Inputs

       .mclk           (app_clk),

       .reset_n        (app_reset_n),

       .clk_div_ratio  (cfg_baud_16x)

   );

wire line_reset_n = app_reset_n; // todo-> create synchronised reset w.r.t line clock

uart_txfsm u_txfsm (

               . reset_n           ( line_reset_n      ),

               . baud_clk_16x      ( line_clk_16x      ),

               . cfg_tx_enable     ( cfg_tx_enable     ),

               . cfg_stop_bit      ( cfg_stop_bit      ),

               . cfg_pri_mod       ( cfg_pri_mod       ),

       // FIFO control signal

               . fifo_empty        ( tx_fifo_rd_empty  ),

               . fifo_rd           ( tx_fifo_rd        ),

               . fifo_data         ( tx_fifo_rd_data   ),

          // Line Interface

               . so                ( so                )

          );

uart_rxfsm u_rxfsm (

               . reset_n           (  line_reset_n     ),

               . baud_clk_16x      (  line_clk_16x     ) ,

               . cfg_rx_enable     (  cfg_rx_enable    ),

               . cfg_stop_bit      (  cfg_stop_bit     ),

               . cfg_pri_mod       (  cfg_pri_mod      ),

               . error_ind         (  error_ind        ),

       // FIFO control signal

               .  fifo_aval        ( !rx_fifo_wr_full  ),

               .  fifo_wr          ( rx_fifo_wr        ),

               .  fifo_data        ( rx_fifo_wr_data   ),

          // Line Interface

               .  si               (si_ss              )

          );

async_fifo #(W,DP,0,0) u_rxfifo (

               .wr_clk             (line_clk_16x       ),

               .wr_reset_n         (line_reset_n       ),

               .wr_en              (rx_fifo_wr         ),

               .wr_data            (rx_fifo_wr_data    ),

               .full               (rx_fifo_wr_full    ), // sync'ed to wr_clk

               .wr_total_free_space(                   ),

               .rd_clk             (app_clk            ),

               .rd_reset_n         (app_reset_n        ),

               .rd_en              (app_rxfifo_rd_en   ),

               .empty              (app_rxfifo_empty   ),  // sync'ed to rd_clk

               .rd_total_aval      (                   ),

               .rd_data            (app_rxfifo_data    )

                   );

async_fifo #(W,DP,0,0) u_txfifo  (

               .wr_clk             (app_clk            ),

               .wr_reset_n         (app_reset_n        ),

               .wr_en              (tx_fifo_wr_en      ),

               .wr_data            (app_txfifo_data    ),

               .full               (app_tx_fifo_full   ), // sync'ed to wr_clk

               .wr_total_free_space(                   ),

               .rd_clk             (line_clk_16x       ),

               .rd_reset_n         (line_reset_n       ),

               .rd_en              (tx_fifo_rd         ),

               .empty              (tx_fifo_rd_empty   ),  // sync'ed to rd_clk

               .rd_total_aval      (                   ),

               .rd_data            (tx_fifo_rd_data    )

                   );

double_sync_low   u_si_sync (

               . in_data           ( si                ),

               . out_clk           (line_clk_16x       ),

               . out_rst_n         (line_reset_n       ),

               . out_data          (si_ss              )

          );

wire   frm_error          = (error_ind == 2'b01);

wire   par_error          = (error_ind == 2'b10);

wire   rx_fifo_full_err   = (error_ind == 2'b11);

double_sync_low   u_frm_err (

               . in_data           ( frm_error        ),

               . out_clk           ( app_clk          ),

               . out_rst_n         ( app_reset_n      ),

               . out_data          ( frm_error_o      )

          );

double_sync_low   u_par_err (

               . in_data           ( par_error        ),

               . out_clk           ( app_clk          ),

               . out_rst_n         ( app_reset_n      ),

               . out_data          ( par_error_o      )

          );

double_sync_low   u_rxfifo_err (

               . in_data           ( rx_fifo_full_err ),

               . out_clk           ( app_clk          ),

               . out_rst_n         ( app_reset_n      ),

               . out_data          ( rx_fifo_full_err_o  )

          );

endmodule