uart_receiver.v

vlsi UART referene, use UART0_3

//////////////////////////////////////////////////////////////////////
////                                                              ////
////  uart_receiver.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 receiver logic                                    ////
////                                                              ////
////  Known problems (limits):                                    ////
////  None known                                                  ////
////                                                              ////
////  To Do:                                                      ////
////  Thourough testing.                                          ////
////                                                              ////
////  Author(s):                                                  ////
////      - [e-mail]                                  ////
////      - Jacob Gorban                                          ////
////      - Igor Mohor ([e-mail])                      ////
////                                                              ////
////  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: uart_receiver.v,v $
// Revision 1.31  2004/06/18 14:46:15  tadejm
// Brandl Tobias repaired a bug regarding frame error in receiver when brake is received.
//
// Revision 1.29  2002/07/29 21:16:18  gorban
// The uart_defines.v file is included again in sources.
//
// Revision 1.28  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 1.27  2001/12/30 20:39:13  mohor
// More than one character was stored in case of break. End of the break
// was not detected correctly.
//
// Revision 1.26  2001/12/20 13:28:27  mohor
// Missing declaration of rf_push_q fixed.
//
// Revision 1.25  2001/12/20 13:25:46  mohor
// rx push changed to be only one cycle wide.
//
// Revision 1.24  2001/12/19 08:03:34  mohor
// Warnings cleared.
//
// Revision 1.23  2001/12/19 07:33:54  mohor
// Synplicity was having troubles with the comment.
//
// Revision 1.22  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 1.21  2001/12/13 10:31:16  mohor
// timeout irq must be set regardless of the rda irq (rda irq does not reset the
// timeout counter).
//
// Revision 1.20  2001/12/10 19:52:05  gorban
// Igor fixed break condition bugs
//
// Revision 1.19  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 1.18  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 1.17  2001/11/28 19:36:39  gorban
// Fixed: timeout and break didn't pay attention to current data format when counting time
//
// Revision 1.16  2001/11/27 22:17:09  gorban
// Fixed bug that prevented synthesis in uart_receiver.v
//
// Revision 1.15  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 1.14  2001/11/10 12:43:21  gorban
// Logic Synthesis bugs fixed. Some other minor changes
//
// Revision 1.13  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 1.12  2001/11/07 17:51:52  gorban
// Heavily rewritten interrupt and LSR subsystems.
// Many bugs hopefully squashed.
//
// Revision 1.11  2001/10/31 15:19:22  gorban
// Fixes to break and timeout conditions
//
// 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  2001/08/23 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 1.6  2001/06/23 11:21:48  gorban
// DL made 16-bit long. Fixed transmission/reception bugs.
//
// Revision 1.5  2001/06/02 14:28:14  gorban
// Fixed receiver and transmitter. Major bug fixed.
//
// Revision 1.4  2001/05/31 20:08:01  gorban
// FIFO changes and other corrections.
//
// Revision 1.3  2001/05/27 17:37:49  gorban
// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.
//
// Revision 1.2  2001/05/21 19:12:02  gorban
// Corrected some Linter messages.
//
// Revision 1.1  2001/05/17 18:34:18  gorban
// First 'stable' release. Should be sythesizable now. Also added new header.
//
// Revision 1.0  2001-05-17 21:27:11+02  jacob
// Initial revision
//
//

// synopsys translate_off
`include "timescale.v"
// synopsys translate_on

`include "uart_defines.v"

module uart_receiver (clk, rst_i, lcr, rf_pop, srx_pad_i, enable, 
				counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask, rstate, rf_push_pulse);

input				clk;
input				rst_i;
input	[7:0]	lcr;
input				rf_pop;
input				srx_pad_i;
input				enable;
input				rx_reset;
input       lsr_mask;

output	[9:0]			counter_t;
output	[`UART_FIFO_COUNTER_W-1:0]	rf_count;
output	[`UART_FIFO_REC_WIDTH-1:0]	rf_data_out;
output				rf_overrun;
output				rf_error_bit;
output [3:0] 		rstate;
output 				rf_push_pulse;

reg	[3:0]	rstate;
reg	[3:0]	rcounter16;
reg	[2:0]	rbit_counter;
reg	[7:0]	rshift;			// receiver shift register
reg		rparity;		// received parity
reg		rparity_error;
reg		rframing_error;		// framing error flag
reg		rbit_in;
reg		rparity_xor;
reg	[7:0]	counter_b;	// counts the 0 (low) signals
reg   rf_push_q;