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//////////////////////////////////////////////////////////////////////
//// ////
//// uart_tfifo.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 transmitter FIFO ////
//// ////
//// To Do: ////
//// Nothing. ////
//// ////
//// Author(s): ////
//// - gorban@opencores.org ////
//// - Jacob Gorban ////
//// - Igor Mohor (igorm@opencores.org) ////
//// ////
//// Created: 2001/05/12 ////
//// Last Updated: 2002/07/22 ////
//// (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: uart_tfifo.v,v $
// Revision 1.2 2002/07/29 21:16:18 gorban
// The uart_defines.v file is included again in sources.
//
// Revision 1.1 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 1.16 2001/12/20 13:25:46 mohor
// rx push changed to be only one cycle wide.
//
// Revision 1.15 2001/12/18 09:01:07 mohor
// Bug that was entered in the last update fixed (rx state machine).
//
// Revision 1.14 2001/12/17 14:46:48 mohor
// overrun signal was moved to separate block because many sequential lsr
// reads were preventing data from being written to rx fifo.
// underrun signal was not used and was removed from the project.
//
// Revision 1.13 2001/11/26 21:38:54 gorban
// Lots of fixes:
// Break condition wasn't handled correctly at all.
// LSR bits could lose their values.
// LSR value after reset was wrong.
// Timing of THRE interrupt signal corrected.
// LSR bit 0 timing corrected.
//
// Revision 1.12 2001/11/08 14:54:23 mohor
// Comments in Slovene language deleted, few small fixes for better work of
// old tools. IRQs need to be fix.
//
// Revision 1.11 2001/11/07 17:51:52 gorban
// Heavily rewritten interrupt and LSR subsystems.
// Many bugs hopefully squashed.
//
// Revision 1.10 2001/10/20 09:58:40 gorban
// Small synopsis fixes
//
// Revision 1.9 2001/08/24 21:01:12 mohor
// Things connected to parity changed.
// Clock devider changed.
//
// Revision 1.8 2001/08/24 08:48:10 mohor
// FIFO was not cleared after the data was read bug fixed.
//
// 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 1.3 2001/05/31 20:08:01 gorban
// FIFO changes and other corrections.
//
// Revision 1.3 2001/05/27 17:37:48 gorban
// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.
//
// 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 21:27:12+02 jacob
// Initial revision
//
//
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "uart_defines.v"
module uart_tfifo (clk,
wb_rst_i, data_in, data_out,
// Control signals
push, // push strobe, active high
pop, // pop strobe, active high
// status signals
overrun,
count,
fifo_reset,
reset_status
);
// FIFO parameters
parameter fifo_width = `UART_FIFO_WIDTH;
parameter fifo_depth = `UART_FIFO_DEPTH;
parameter fifo_pointer_w = `UART_FIFO_POINTER_W;
parameter fifo_counter_w = `UART_FIFO_COUNTER_W;
input clk;
input wb_rst_i;
input push;
input pop;
input [fifo_width-1:0] data_in;
input fifo_reset;
input reset_status;
output [fifo_width-1:0] data_out;
output overrun;
output [fifo_counter_w-1:0] count;
wire [fifo_width-1:0] data_out;
// FIFO pointers
reg [fifo_pointer_w-1:0] top;
reg [fifo_pointer_w-1:0] bottom;
reg [fifo_counter_w-1:0] count;
reg overrun;
wire [fifo_pointer_w-1:0] top_plus_1 = top + 1'b1;
raminfr #(fifo_pointer_w,fifo_width,fifo_depth) tfifo
(.clk(clk),
.we(push),
.a(top),
.dpra(bottom),
.di(data_in),
.dpo(data_out)
);
always @(posedge clk or posedge wb_rst_i) // synchronous FIFO
begin
if (wb_rst_i)
begin
top <= #1 0;
bottom <= #1 1'b0;
count <= #1 0;
end
else
if (fifo_reset) begin
top <= #1 0;
bottom <= #1 1'b0;
count <= #1 0;
end
else
begin
case ({push, pop})
2'b10 : if (count<fifo_depth) // overrun condition
begin
top <= #1 top_plus_1;
count <= #1 count + 1'b1;
end
2'b01 : if(count>0)
begin
bottom <= #1 bottom + 1'b1;
count <= #1 count - 1'b1;
end
2'b11 : begin
bottom <= #1 bottom + 1'b1;
top <= #1 top_plus_1;
end
default: ;
endcase
end
end // always
always @(posedge clk or posedge wb_rst_i) // synchronous FIFO
begin
if (wb_rst_i)
overrun <= #1 1'b0;
else
if(fifo_reset | reset_status)
overrun <= #1 1'b0;
else
if(push & (count==fifo_depth))
overrun <= #1 1'b1;
end // always
endmodule
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