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

////                                                              ////

////  uart_wb.v                                                   ////

////                                                              ////

////                                                              ////

////  This file is part of the "UART 16550 compatible" project    ////

////  http://www.opencores.org/cores/uart16550/                   ////

////                                                              ////

////  Documentation related to this project:                      ////

////  - http://www.opencores.org/cores/uart16550/                 ////

////                                                              ////

////  Projects compatibility:                                     ////

////  - WISHBONE                                                  ////

////  RS232 Protocol                                              ////

////  16550D uart (mostly supported)                              ////

////                                                              ////

////  Overview (main Features):                                   ////

////  UART core WISHBONE interface.                               ////

////                                                              ////

////  Known problems (limits):                                    ////

////  Inserts one wait state on all transfers.                    ////

////  Note affected signals and the way they are affected.        ////

////                                                              ////

////  To Do:                                                      ////

////  Nothing.                                                    ////

////                                                              ////

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

////      - gorban@opencores.org                                  ////

////      - Jacob Gorban                                          ////

////      - Igor Mohor (igorm@opencores.org)                      ////

////                                                              ////

////  Created:        2001/05/12                                  ////

////  Last Updated:   2001/05/17                                  ////

////                  (See log for the revision history)          ////

////                                                              ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2000, 2001 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 1.16  2002/07/29 21:16:18  gorban

// The uart_defines.v file is included again in sources.

//

// Revision 1.15  2002/07/22 23:02:23  gorban

// Bug Fixes:

//  * Possible loss of sync and bad reception of stop bit on slow baud rates fixed.

//   Problem reported by Kenny.Tung.

//  * Bad (or lack of ) loopback handling fixed. Reported by Cherry Withers.

//

// Improvements:

//  * Made FIFO's as general inferrable memory where possible.

//  So on FPGA they should be inferred as RAM (Distributed RAM on Xilinx).

//  This saves about 1/3 of the Slice count and reduces P&R and synthesis times.

//

//  * Added optional baudrate output (baud_o).

//  This is identical to BAUDOUT* signal on 16550 chip.

//  It outputs 16xbit_clock_rate - the divided clock.

//  It's disabled by default. Define UART_HAS_BAUDRATE_OUTPUT to use.

//

// Revision 1.12  2001/12/19 08:03:34  mohor

// Warnings cleared.

//

// Revision 1.11  2001/12/06 14:51:04  gorban

// Bug in LSR[0] is fixed.

// All WISHBONE signals are now sampled, so another wait-state is introduced on all transfers.

//

// Revision 1.10  2001/12/03 21:44:29  gorban

// Updated specification documentation.

// Added full 32-bit data bus interface, now as default.

// Address is 5-bit wide in 32-bit data bus mode.

// Added wb_sel_i input to the core. It's used in the 32-bit mode.

// Added debug interface with two 32-bit read-only registers in 32-bit mode.

// Bits 5 and 6 of LSR are now only cleared on TX FIFO write.

// My small test bench is modified to work with 32-bit mode.

//

// Revision 1.9  2001/10/20 09:58:40  gorban

// Small synopsis fixes

//

// Revision 1.8  2001/08/24 21:01:12  mohor

// Things connected to parity changed.

// Clock devider changed.

//

// Revision 1.7  2001/08/23 16:05:05  mohor

// Stop bit bug fixed.

// Parity bug fixed.

// WISHBONE read cycle bug fixed,

// OE indicator (Overrun Error) bug fixed.

// PE indicator (Parity Error) bug fixed.

// Register read bug fixed.

//

// Revision 1.4  2001/05/31 20:08:01  gorban

// FIFO changes and other corrections.

//

// Revision 1.3  2001/05/21 19:12:01  gorban

// Corrected some Linter messages.

//

// Revision 1.2  2001/05/17 18:34:18  gorban

// First 'stable' release. Should be sythesizable now. Also added new header.

//

// Revision 1.0  2001-05-17 21:27:13+02  jacob

// Initial revision

//

//

// UART core WISHBONE interface 

//

// Author: Jacob Gorban   (jacob.gorban@flextronicssemi.com)

// Company: Flextronics Semiconductor

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "uart_defines.v"

module uart_wb (clk, wb_rst_i,

        wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o, wb_adr_i,

        wb_adr_int, wb_dat_i, wb_dat_o, wb_dat8_i, wb_dat8_o, wb_dat32_o, wb_sel_i,

        we_o, re_o // Write and read enable output for the core

);

input             clk;

// WISHBONE interface   

input             wb_rst_i;

input             wb_we_i;

input             wb_stb_i;

input             wb_cyc_i;

input [3:0]   wb_sel_i;

input [`UART_ADDR_WIDTH-1:0]     wb_adr_i; //WISHBONE address line

`ifdef DATA_BUS_WIDTH_8

input [7:0]  wb_dat_i; //input WISHBONE bus 

output [7:0] wb_dat_o;

reg [7:0]         wb_dat_o;

wire [7:0]        wb_dat_i;

reg [7:0]         wb_dat_is;

`else // for 32 data bus mode

input [31:0]  wb_dat_i; //input WISHBONE bus 

output [31:0] wb_dat_o;

reg [31:0]         wb_dat_o;

wire [31:0]   wb_dat_i;

reg [31:0]         wb_dat_is;

`endif // !`ifdef DATA_BUS_WIDTH_8

output [`UART_ADDR_WIDTH-1:0]    wb_adr_int; // internal signal for address bus

input [7:0]   wb_dat8_o; // internal 8 bit output to be put into wb_dat_o

output [7:0]  wb_dat8_i;

input [31:0]  wb_dat32_o; // 32 bit data output (for debug interface)

output            wb_ack_o;

output            we_o;

output            re_o;

wire                      we_o;

reg                       wb_ack_o;

reg [7:0]          wb_dat8_i;

wire [7:0]         wb_dat8_o;

wire [`UART_ADDR_WIDTH-1:0]      wb_adr_int; // internal signal for address bus

reg [`UART_ADDR_WIDTH-1:0]       wb_adr_is;

reg                                                             wb_we_is;

reg                                                             wb_cyc_is;

reg                                                             wb_stb_is;

reg [3:0]                                                wb_sel_is;

wire [3:0]   wb_sel_i;

reg                      wre ;// timing control signal for write or read enable

// wb_ack_o FSM

reg [1:0]         wbstate;

always  @(posedge clk or posedge wb_rst_i)

        if (wb_rst_i) begin

                wb_ack_o <=  1'b0;

                wbstate <=  0;

                wre <=  1'b1;

        end else

                case (wbstate)

                        0: begin

                                if (wb_stb_is & wb_cyc_is) begin

                                        wre <=  0;

                                        wbstate <=  1;

                                        wb_ack_o <=  1;

                                end else begin

                                        wre <=  1;

                                        wb_ack_o <=  0;

                                end

                        end

                        1: begin

                           wb_ack_o <=  0;

                                wbstate <=  2;

                                wre <=  0;

                        end

                        2,3: begin

                                wb_ack_o <=  0;

                                wbstate <=  0;

                                wre <=  0;

                        end

                endcase

assign we_o =  wb_we_is & wb_stb_is & wb_cyc_is & wre ; //WE for registers      

assign re_o = ~wb_we_is & wb_stb_is & wb_cyc_is & wre ; //RE for registers      

// Sample input signals

always  @(posedge clk or posedge wb_rst_i)

        if (wb_rst_i) begin

                wb_adr_is <=  0;

                wb_we_is <=  0;

                wb_cyc_is <=  0;

                wb_stb_is <=  0;

                wb_dat_is <=  0;

                wb_sel_is <=  0;

        end else begin

                wb_adr_is <=  wb_adr_i;

                wb_we_is <=  wb_we_i;

                wb_cyc_is <=  wb_cyc_i;

                wb_stb_is <=  wb_stb_i;

                wb_dat_is <=  wb_dat_i;

                wb_sel_is <=  wb_sel_i;

        end

`ifdef DATA_BUS_WIDTH_8 // 8-bit data bus

always @(posedge clk or posedge wb_rst_i)

        if (wb_rst_i)

                wb_dat_o <=  0;

        else

                wb_dat_o <=  wb_dat8_o;

always @(wb_dat_is)

        wb_dat8_i = wb_dat_is;

assign wb_adr_int = wb_adr_is;

`else // 32-bit bus

// put output to the correct byte in 32 bits using select line

always @(posedge clk or posedge wb_rst_i)

        if (wb_rst_i)

                wb_dat_o <=  0;

        else if (re_o)

                case (wb_sel_is)

                        4'b0001: wb_dat_o <=  {24'b0, wb_dat8_o};

                        4'b0010: wb_dat_o <=  {16'b0, wb_dat8_o, 8'b0};

                        4'b0100: wb_dat_o <=  {8'b0, wb_dat8_o, 16'b0};

                        4'b1000: wb_dat_o <=  {wb_dat8_o, 24'b0};

                        4'b1111: wb_dat_o <=  wb_dat32_o; // debug interface output

                        default: wb_dat_o <=  0;

                endcase // case(wb_sel_i)

reg [1:0] wb_adr_int_lsb;

always @(wb_sel_is or wb_dat_is)

begin

        case (wb_sel_is)

                4'b0001 : wb_dat8_i = wb_dat_is[7:0];

                4'b0010 : wb_dat8_i = wb_dat_is[15:8];

                4'b0100 : wb_dat8_i = wb_dat_is[23:16];

                4'b1000 : wb_dat8_i = wb_dat_is[31:24];

                default : wb_dat8_i = wb_dat_is[7:0];

        endcase // case(wb_sel_i)

  `ifdef LITLE_ENDIAN

        case (wb_sel_is)

                4'b0001 : wb_adr_int_lsb = 2'h0;

                4'b0010 : wb_adr_int_lsb = 2'h1;

                4'b0100 : wb_adr_int_lsb = 2'h2;

                4'b1000 : wb_adr_int_lsb = 2'h3;

                default : wb_adr_int_lsb = 2'h0;

        endcase // case(wb_sel_i)

  `else

        case (wb_sel_is)

                4'b0001 : wb_adr_int_lsb = 2'h3;

                4'b0010 : wb_adr_int_lsb = 2'h2;

                4'b0100 : wb_adr_int_lsb = 2'h1;

                4'b1000 : wb_adr_int_lsb = 2'h0;

                default : wb_adr_int_lsb = 2'h0;

        endcase // case(wb_sel_i)

  `endif

end

assign wb_adr_int = {wb_adr_is[`UART_ADDR_WIDTH-1:2], wb_adr_int_lsb};

`endif // !`ifdef DATA_BUS_WIDTH_8

endmodule