Add uart16550 files from fusesoc

These are needed for synthesis that doesn't use fusesoc natively.

These were pulled in via 'fusesoc fetch ::uart16550:1.5.5-r1'

Signed-off-by: Michael Neuling <mikey@neuling.org>

uart16550/raminfr.v

@@ -0,0 +1,111 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  raminfr.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):                                   ////
+////  Inferrable Distributed RAM for FIFOs                        ////
+////                                                              ////
+////  Known problems (limits):                                    ////
+////  None                .                                       ////
+////                                                              ////
+////  To Do:                                                      ////
+////  Nothing so far.                                             ////
+////                                                              ////
+////  Author(s):                                                  ////
+////      - gorban@opencores.org                                  ////
+////      - Jacob Gorban                                          ////
+////                                                              ////
+////  Created:        2002/07/22                                  ////
+////  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: not supported by cvs2svn $
+// 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.
+//
+
+//Following is the Verilog code for a dual-port RAM with asynchronous read. 
+module raminfr   
+        (clk, we, a, dpra, di, dpo); 
+
+parameter addr_width = 4;
+parameter data_width = 8;
+parameter depth = 16;
+
+input clk;   
+input we;   
+input  [addr_width-1:0] a;   
+input  [addr_width-1:0] dpra;   
+input  [data_width-1:0] di;   
+//output [data_width-1:0] spo;   
+output [data_width-1:0] dpo;   
+reg    [data_width-1:0] ram [depth-1:0]; 
+
+wire [data_width-1:0] dpo;
+wire  [data_width-1:0] di;   
+wire  [addr_width-1:0] a;   
+wire  [addr_width-1:0] dpra;   
+ 
+  always @(posedge clk) begin   
+    if (we)   
+      ram[a] <= di;   
+  end   
+//  assign spo = ram[a];   
+  assign dpo = ram[dpra];   
+endmodule 
+

uart16550/uart_defines.v

@@ -0,0 +1,233 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_defines.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):                                   ////
+////  Defines of the Core                                         ////
+////                                                              ////
+////  Known problems (limits):                                    ////
+////  None                                                        ////
+////                                                              ////
+////  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 1.13  2003/06/11 16:37:47  gorban
+// This fixes errors in some cases when data is being read and put to the FIFO at the same time. Patch is submitted by Scott Furman. Update is very recommended.
+//
+// Revision 1.12  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 1.10  2001/12/11 08:55:40  mohor
+// Scratch register define added.
+//
+// Revision 1.9  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 1.8  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 1.7  2001/08/24 21:01:12  mohor
+// Things connected to parity changed.
+// Clock devider changed.
+//
+// Revision 1.6  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 1.5  2001/05/31 20:08:01  gorban
+// FIFO changes and other corrections.
+//
+// Revision 1.4  2001/05/21 19:12:02  gorban
+// Corrected some Linter messages.
+//
+// Revision 1.3  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
+//
+//
+
+// Uncomment this if you want your UART to have
+// 16xBaudrate output port.
+// If defined, the enable signal will be used to drive baudrate_o signal
+// It's frequency is 16xbaudrate
+
+// `define UART_HAS_BAUDRATE_OUTPUT
+
+// Register addresses
+`define UART_REG_RB	3'd0	// receiver buffer
+`define UART_REG_TR  3'd0	// transmitter
+`define UART_REG_IE	3'd1	// Interrupt enable
+`define UART_REG_II  3'd2	// Interrupt identification
+`define UART_REG_FC  3'd2	// FIFO control
+`define UART_REG_LC	3'd3	// Line Control
+`define UART_REG_MC	3'd4	// Modem control
+`define UART_REG_LS  3'd5	// Line status
+`define UART_REG_MS  3'd6	// Modem status
+`define UART_REG_SR  3'd7	// Scratch register
+`define UART_REG_DL1	3'd0	// Divisor latch bytes (1-2)
+`define UART_REG_DL2	3'd1
+
+// Interrupt Enable register bits
+`define UART_IE_RDA	0	// Received Data available interrupt
+`define UART_IE_THRE	1	// Transmitter Holding Register empty interrupt
+`define UART_IE_RLS	2	// Receiver Line Status Interrupt
+`define UART_IE_MS	3	// Modem Status Interrupt
+
+// Interrupt Identification register bits
+`define UART_II_IP	0	// Interrupt pending when 0
+`define UART_II_II	3:1	// Interrupt identification
+
+// Interrupt identification values for bits 3:1
+`define UART_II_RLS	3'b011	// Receiver Line Status
+`define UART_II_RDA	3'b010	// Receiver Data available
+`define UART_II_TI	3'b110	// Timeout Indication
+`define UART_II_THRE	3'b001	// Transmitter Holding Register empty
+`define UART_II_MS	3'b000	// Modem Status
+
+// FIFO Control Register bits
+`define UART_FC_TL	1:0	// Trigger level
+
+// FIFO trigger level values
+`define UART_FC_1		2'b00
+`define UART_FC_4		2'b01
+`define UART_FC_8		2'b10
+`define UART_FC_14	2'b11
+
+// Line Control register bits
+`define UART_LC_BITS	1:0	// bits in character
+`define UART_LC_SB	2	// stop bits
+`define UART_LC_PE	3	// parity enable
+`define UART_LC_EP	4	// even parity
+`define UART_LC_SP	5	// stick parity
+`define UART_LC_BC	6	// Break control
+`define UART_LC_DL	7	// Divisor Latch access bit
+
+// Modem Control register bits
+`define UART_MC_DTR	0
+`define UART_MC_RTS	1
+`define UART_MC_OUT1	2
+`define UART_MC_OUT2	3
+`define UART_MC_LB	4	// Loopback mode
+
+// Line Status Register bits
+`define UART_LS_DR	0	// Data ready
+`define UART_LS_OE	1	// Overrun Error
+`define UART_LS_PE	2	// Parity Error
+`define UART_LS_FE	3	// Framing Error
+`define UART_LS_BI	4	// Break interrupt
+`define UART_LS_TFE	5	// Transmit FIFO is empty
+`define UART_LS_TE	6	// Transmitter Empty indicator
+`define UART_LS_EI	7	// Error indicator
+
+// Modem Status Register bits
+`define UART_MS_DCTS	0	// Delta signals
+`define UART_MS_DDSR	1
+`define UART_MS_TERI	2
+`define UART_MS_DDCD	3
+`define UART_MS_CCTS	4	// Complement signals
+`define UART_MS_CDSR	5
+`define UART_MS_CRI	6
+`define UART_MS_CDCD	7
+
+// FIFO parameter defines
+
+`define UART_FIFO_WIDTH	8
+`define UART_FIFO_DEPTH	16
+`define UART_FIFO_POINTER_W	4
+`define UART_FIFO_COUNTER_W	5
+// receiver fifo has width 11 because it has break, parity and framing error bits
+`define UART_FIFO_REC_WIDTH  11
+
+
+`define VERBOSE_WB  0           // All activity on the WISHBONE is recorded
+`define VERBOSE_LINE_STATUS 0   // Details about the lsr (line status register)
+`define FAST_TEST   1           // 64/1024 packets are sent
+
+
+
+
+
+
+

uart16550/uart_receiver.v

@@ -0,0 +1,475 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  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):                                                  ////
+////      - 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 1.29  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
+//
+//
+
+`include "uart_defines.v"
+
+module uart_receiver (clk, wb_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				wb_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		rparity_xor;
+reg	[7:0]	counter_b;	// counts the 0 (low) signals
+reg   rf_push_q;
+
+// RX FIFO signals
+reg	[`UART_FIFO_REC_WIDTH-1:0]	rf_data_in;
+wire	[`UART_FIFO_REC_WIDTH-1:0]	rf_data_out;
+wire      rf_push_pulse;
+reg				rf_push;
+wire				rf_pop;
+wire				rf_overrun;
+wire	[`UART_FIFO_COUNTER_W-1:0]	rf_count;
+wire				rf_error_bit; // an error (parity or framing) is inside the fifo
+wire 				break_error = (counter_b == 0);
+
+// RX FIFO instance
+uart_rfifo #(`UART_FIFO_REC_WIDTH) fifo_rx(
+	.clk(		clk		), 
+	.wb_rst_i(	wb_rst_i	),
+	.data_in(	rf_data_in	),
+	.data_out(	rf_data_out	),
+	.push(		rf_push_pulse		),
+	.pop(		rf_pop		),
+	.overrun(	rf_overrun	),
+	.count(		rf_count	),
+	.error_bit(	rf_error_bit	),
+	.fifo_reset(	rx_reset	),
+	.reset_status(lsr_mask)
+);
+
+wire 		rcounter16_eq_7 = (rcounter16 == 4'd7);
+wire		rcounter16_eq_0 = (rcounter16 == 4'd0);
+
+wire [3:0] rcounter16_minus_1 = rcounter16 - 3'd1;
+
+parameter  sr_idle 					= 4'd0;
+parameter  sr_rec_start 			= 4'd1;
+parameter  sr_rec_bit 				= 4'd2;
+parameter  sr_rec_parity			= 4'd3;
+parameter  sr_rec_stop 				= 4'd4;
+parameter  sr_check_parity 		= 4'd5;
+parameter  sr_rec_prepare 			= 4'd6;
+parameter  sr_end_bit				= 4'd7;
+parameter  sr_ca_lc_parity	      = 4'd8;
+parameter  sr_wait1 					= 4'd9;
+parameter  sr_push 					= 4'd10;
+
+
+always @(posedge clk or posedge wb_rst_i)
+begin
+  if (wb_rst_i)
+  begin
+     rstate 			<= sr_idle;
+	  rcounter16 			<= 0;
+	  rbit_counter 		<= 0;
+	  rparity_xor 		<= 1'b0;
+	  rframing_error 	<= 1'b0;
+	  rparity_error 		<= 1'b0;
+	  rparity 				<= 1'b0;
+	  rshift 				<= 0;
+	  rf_push 				<= 1'b0;
+	  rf_data_in 			<= 0;
+  end
+  else
+  if (enable)
+  begin
+	case (rstate)
+	sr_idle : begin
+			rf_push 			  <= 1'b0;
+			rf_data_in 	  <= 0;
+			rcounter16 	  <= 4'b1110;
+			if (srx_pad_i==1'b0 & ~break_error)   // detected a pulse (start bit?)
+			begin
+				rstate 		  <= sr_rec_start;
+			end
+		end
+	sr_rec_start :	begin
+  			rf_push 			  <= 1'b0;
+				if (rcounter16_eq_7)    // check the pulse
+					if (srx_pad_i==1'b1)   // no start bit
+						rstate <= sr_idle;
+					else            // start bit detected
+						rstate <= sr_rec_prepare;
+				rcounter16 <= rcounter16_minus_1;
+			end
+	sr_rec_prepare:begin
+				case (lcr[/*`UART_LC_BITS*/1:0])  // number of bits in a word
+				2'b00 : rbit_counter <= 3'b100;
+				2'b01 : rbit_counter <= 3'b101;
+				2'b10 : rbit_counter <= 3'b110;
+				2'b11 : rbit_counter <= 3'b111;
+				endcase
+				if (rcounter16_eq_0)
+				begin
+					rstate		<= sr_rec_bit;
+					rcounter16	<= 4'b1110;
+					rshift		<= 0;
+				end
+				else
+					rstate <= sr_rec_prepare;
+				rcounter16 <= rcounter16_minus_1;
+			end
+	sr_rec_bit :	begin
+				if (rcounter16_eq_0)
+					rstate <= sr_end_bit;
+				if (rcounter16_eq_7) // read the bit
+					case (lcr[/*`UART_LC_BITS*/1:0])  // number of bits in a word
+					2'b00 : rshift[4:0]  <= {srx_pad_i, rshift[4:1]};
+					2'b01 : rshift[5:0]  <= {srx_pad_i, rshift[5:1]};
+					2'b10 : rshift[6:0]  <= {srx_pad_i, rshift[6:1]};
+					2'b11 : rshift[7:0]  <= {srx_pad_i, rshift[7:1]};
+					endcase
+				rcounter16 <= rcounter16_minus_1;
+			end
+	sr_end_bit :   begin
+				if (rbit_counter==3'b0) // no more bits in word
+					if (lcr[`UART_LC_PE]) // choose state based on parity
+						rstate <= sr_rec_parity;
+					else
+					begin
+						rstate <= sr_rec_stop;
+						rparity_error <= 1'b0;  // no parity - no error :)
+					end
+				else		// else we have more bits to read
+				begin
+					rstate <= sr_rec_bit;
+					rbit_counter <= rbit_counter - 3'd1;
+				end
+				rcounter16 <= 4'b1110;
+			end
+	sr_rec_parity: begin
+				if (rcounter16_eq_7)	// read the parity
+				begin
+					rparity <= srx_pad_i;
+					rstate <= sr_ca_lc_parity;
+				end
+				rcounter16 <= rcounter16_minus_1;
+			end
+	sr_ca_lc_parity : begin    // rcounter equals 6
+				rcounter16  <= rcounter16_minus_1;
+				rparity_xor <= ^{rshift,rparity}; // calculate parity on all incoming data
+				rstate      <= sr_check_parity;
+			  end
+	sr_check_parity: begin	  // rcounter equals 5
+				case ({lcr[`UART_LC_EP],lcr[`UART_LC_SP]})
+					2'b00: rparity_error <=  rparity_xor == 0;  // no error if parity 1
+					2'b01: rparity_error <= ~rparity;      // parity should sticked to 1
+					2'b10: rparity_error <=  rparity_xor == 1;   // error if parity is odd
+					2'b11: rparity_error <=  rparity;	  // parity should be sticked to 0
+				endcase
+				rcounter16 <= rcounter16_minus_1;
+				rstate <= sr_wait1;
+			  end
+	sr_wait1 :	if (rcounter16_eq_0)
+			begin
+				rstate <= sr_rec_stop;
+				rcounter16 <= 4'b1110;
+			end
+			else
+				rcounter16 <= rcounter16_minus_1;
+	sr_rec_stop :	begin
+				if (rcounter16_eq_7)	// read the parity
+				begin
+					rframing_error <= !srx_pad_i; // no framing error if input is 1 (stop bit)
+					rstate <= sr_push;
+				end
+				rcounter16 <= rcounter16_minus_1;
+			end
+	sr_push :	begin
+///////////////////////////////////////
+//				$display($time, ": received: %b", rf_data_in);
+        if(srx_pad_i | break_error)
+          begin
+            if(break_error)
+        		  rf_data_in 	<= {8'b0, 3'b100}; // break input (empty character) to receiver FIFO
+            else
+        			rf_data_in  <= {rshift, 1'b0, rparity_error, rframing_error};
+      		  rf_push 		  <= 1'b1;
+    				rstate        <= sr_idle;
+          end
+        else if(~rframing_error)  // There's always a framing before break_error -> wait for break or srx_pad_i
+          begin
+       			rf_data_in  <= {rshift, 1'b0, rparity_error, rframing_error};
+      		  rf_push 		  <= 1'b1;
+      			rcounter16 	  <= 4'b1110;
+    				rstate 		  <= sr_rec_start;
+          end
+                      
+			end
+	default : rstate <= sr_idle;
+	endcase
+  end  // if (enable)
+end // always of receiver
+
+always @ (posedge clk or posedge wb_rst_i)
+begin
+  if(wb_rst_i)
+    rf_push_q <= 0;
+  else
+    rf_push_q <= rf_push;
+end
+
+assign rf_push_pulse = rf_push & ~rf_push_q;
+
+  
+//
+// Break condition detection.
+// Works in conjuction with the receiver state machine
+
+reg 	[9:0]	toc_value; // value to be set to timeout counter
+
+always @(lcr)
+	case (lcr[3:0])
+		4'b0000										: toc_value = 447; // 7 bits
+		4'b0100										: toc_value = 479; // 7.5 bits
+		4'b0001,	4'b1000							: toc_value = 511; // 8 bits
+		4'b1100										: toc_value = 543; // 8.5 bits
+		4'b0010, 4'b0101, 4'b1001				: toc_value = 575; // 9 bits
+		4'b0011, 4'b0110, 4'b1010, 4'b1101	: toc_value = 639; // 10 bits
+		4'b0111, 4'b1011, 4'b1110				: toc_value = 703; // 11 bits
+		4'b1111										: toc_value = 767; // 12 bits
+	endcase // case(lcr[3:0])
+
+wire [7:0] 	brc_value; // value to be set to break counter
+assign 		brc_value = toc_value[9:2]; // the same as timeout but 1 insead of 4 character times
+
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		counter_b <= 8'd159;
+	else
+	if (srx_pad_i)
+		counter_b <= brc_value; // character time length - 1
+	else
+	if(enable & counter_b != 8'b0)            // only work on enable times  break not reached.
+		counter_b <= counter_b - 8'd1;  // decrement break counter
+end // always of break condition detection
+
+///
+/// Timeout condition detection
+reg	[9:0]	counter_t;	// counts the timeout condition clocks
+
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		counter_t <= 10'd639; // 10 bits for the default 8N1
+	else
+		if(rf_push_pulse || rf_pop || rf_count == 0) // counter is reset when RX FIFO is empty, accessed or above trigger level
+			counter_t <= toc_value;
+		else
+		if (enable && counter_t != 10'b0)  // we don't want to underflow
+			counter_t <= counter_t - 10'd1;
+end
+	
+endmodule

uart16550/uart_regs.v

@@ -0,0 +1,888 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_regs.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):                                   ////
+////  Registers of the uart 16550 core                            ////
+////                                                              ////
+////  Known problems (limits):                                    ////
+////  Inserts 1 wait state in all WISHBONE transfers              ////
+////                                                              ////
+////  To Do:                                                      ////
+////  Nothing or verification.                                    ////
+////                                                              ////
+////  Author(s):                                                  ////
+////      - gorban@opencores.org                                  ////
+////      - Jacob Gorban                                          ////
+////      - Igor Mohor (igorm@opencores.org)                      ////
+////                                                              ////
+////  Created:        2001/05/12                                  ////
+////  Last Updated:   (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 1.41  2004/05/21 11:44:41  tadejm
+// Added synchronizer flops for RX input.
+//
+// Revision 1.40  2003/06/11 16:37:47  gorban
+// This fixes errors in some cases when data is being read and put to the FIFO at the same time. Patch is submitted by Scott Furman. Update is very recommended.
+//
+// Revision 1.39  2002/07/29 21:16:18  gorban
+// The uart_defines.v file is included again in sources.
+//
+// Revision 1.38  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 1.37  2001/12/27 13:24:09  mohor
+// lsr[7] was not showing overrun errors.
+//
+// Revision 1.36  2001/12/20 13:25:46  mohor
+// rx push changed to be only one cycle wide.
+//
+// Revision 1.35  2001/12/19 08:03:34  mohor
+// Warnings cleared.
+//
+// Revision 1.34  2001/12/19 07:33:54  mohor
+// Synplicity was having troubles with the comment.
+//
+// Revision 1.33  2001/12/17 10:14:43  mohor
+// Things related to msr register changed. After THRE IRQ occurs, and one
+// character is written to the transmit fifo, the detection of the THRE bit in the
+// LSR is delayed for one character time.
+//
+// Revision 1.32  2001/12/14 13:19:24  mohor
+// MSR register fixed.
+//
+// Revision 1.31  2001/12/14 10:06:58  mohor
+// After reset modem status register MSR should be reset.
+//
+// Revision 1.30  2001/12/13 10:09:13  mohor
+// thre irq should be cleared only when being source of interrupt.
+//
+// Revision 1.29  2001/12/12 09:05:46  mohor
+// LSR status bit 0 was not cleared correctly in case of reseting the FCR (rx fifo).
+//
+// Revision 1.28  2001/12/10 19:52:41  gorban
+// Scratch register added
+//
+// Revision 1.27  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 1.26  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 1.25  2001/11/28 19:36:39  gorban
+// Fixed: timeout and break didn't pay attention to current data format when counting time
+//
+// Revision 1.24  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 1.23  2001/11/12 21:57:29  gorban
+// fixed more typo bugs
+//
+// Revision 1.22  2001/11/12 15:02:28  mohor
+// lsr1r error fixed.
+//
+// Revision 1.21  2001/11/12 14:57:27  mohor
+// ti_int_pnd error fixed.
+//
+// Revision 1.20  2001/11/12 14:50:27  mohor
+// ti_int_d error fixed.
+//
+// Revision 1.19  2001/11/10 12:43:21  gorban
+// Logic Synthesis bugs fixed. Some other minor changes
+//
+// Revision 1.18  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 1.17  2001/11/07 17:51:52  gorban
+// Heavily rewritten interrupt and LSR subsystems.
+// Many bugs hopefully squashed.
+//
+// Revision 1.16  2001/11/02 09:55:16  mohor
+// no message
+//
+// Revision 1.15  2001/10/31 15:19:22  gorban
+// Fixes to break and timeout conditions
+//
+// Revision 1.14  2001/10/29 17:00:46  gorban
+// fixed parity sending and tx_fifo resets over- and underrun
+//
+// Revision 1.13  2001/10/20 09:58:40  gorban
+// Small synopsis fixes
+//
+// Revision 1.12  2001/10/19 16:21:40  gorban
+// Changes data_out to be synchronous again as it should have been.
+//
+// Revision 1.11  2001/10/18 20:35:45  gorban
+// small fix
+//
+// Revision 1.10  2001/08/24 21:01:12  mohor
+// Things connected to parity changed.
+// Clock devider changed.
+//
+// Revision 1.9  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 1.10  2001/06/23 11:21:48  gorban
+// DL made 16-bit long. Fixed transmission/reception bugs.
+//
+// Revision 1.9  2001/05/31 20:08:01  gorban
+// FIFO changes and other corrections.
+//
+// Revision 1.8  2001/05/29 20:05:04  gorban
+// Fixed some bugs and synthesis problems.
+//
+// Revision 1.7  2001/05/27 17:37:49  gorban
+// Fixed many bugs. Updated spec. Changed FIFO files structure. See CHANGES.txt file.
+//
+// Revision 1.6  2001/05/21 19:12:02  gorban
+// Corrected some Linter messages.
+//
+// Revision 1.5  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
+//
+//
+
+`include "uart_defines.v"
+
+`define UART_DL1 7:0
+`define UART_DL2 15:8
+
+module uart_regs
+#(parameter SIM = 0)
+ (clk,
+	wb_rst_i, wb_addr_i, wb_dat_i, wb_dat_o, wb_we_i, wb_re_i, 
+
+// additional signals
+	modem_inputs,
+	stx_pad_o, srx_pad_i,
+
+	rts_pad_o, dtr_pad_o, int_o
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+	, baud_o
+`endif
+
+	);
+
+input 									clk;
+input 									wb_rst_i;
+input [2:0] 		wb_addr_i;
+input [7:0] 							wb_dat_i;
+output [7:0] 							wb_dat_o;
+input 									wb_we_i;
+input 									wb_re_i;
+
+output 									stx_pad_o;
+input 									srx_pad_i;
+
+input [3:0] 							modem_inputs;
+output 									rts_pad_o;
+output 									dtr_pad_o;
+output 									int_o;
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+output	baud_o;
+`endif
+
+wire [3:0] 								modem_inputs;
+reg 										enable;
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+assign baud_o = enable; // baud_o is actually the enable signal
+`endif
+
+
+wire 										stx_pad_o;		// received from transmitter module
+wire 										srx_pad_i;
+wire 										srx_pad;
+
+reg [7:0] 								wb_dat_o;
+
+wire [2:0] 		wb_addr_i;
+wire [7:0] 								wb_dat_i;
+
+
+reg [3:0] 								ier;
+reg [3:0] 								iir;
+reg [1:0] 								fcr;  /// bits 7 and 6 of fcr. Other bits are ignored
+reg [4:0] 								mcr;
+reg [7:0] 								lcr;
+reg [7:0] 								msr;
+reg [15:0] 								dl;  // 32-bit divisor latch
+reg [7:0] 								scratch; // UART scratch register
+reg 										start_dlc; // activate dlc on writing to UART_DL1
+reg 										lsr_mask_d; // delay for lsr_mask condition
+reg 										msi_reset; // reset MSR 4 lower bits indicator
+//reg 										threi_clear; // THRE interrupt clear flag
+reg [15:0] 								dlc;  // 32-bit divisor latch counter
+reg 										int_o;
+
+reg [3:0] 								trigger_level; // trigger level of the receiver FIFO
+reg 										rx_reset;
+reg 										tx_reset;
+
+wire 										dlab;			   // divisor latch access bit
+wire 										cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i; // modem status bits
+wire 										loopback;		   // loopback bit (MCR bit 4)
+wire 										cts, dsr, ri, dcd;	   // effective signals
+wire                    cts_c, dsr_c, ri_c, dcd_c; // Complement effective signals (considering loopback)
+wire 										rts_pad_o, dtr_pad_o;		   // modem control outputs
+
+// LSR bits wires and regs
+wire [7:0] 								lsr;
+wire 										lsr0, lsr1, lsr2, lsr3, lsr4, lsr5, lsr6, lsr7;
+reg										lsr0r, lsr1r, lsr2r, lsr3r, lsr4r, lsr5r, lsr6r, lsr7r;
+wire 										lsr_mask; // lsr_mask
+
+//
+// ASSINGS
+//
+
+assign 									lsr[7:0] = { lsr7r, lsr6r, lsr5r, lsr4r, lsr3r, lsr2r, lsr1r, lsr0r };
+
+assign 									{cts_pad_i, dsr_pad_i, ri_pad_i, dcd_pad_i} = modem_inputs;
+assign 									{cts, dsr, ri, dcd} = ~{cts_pad_i,dsr_pad_i,ri_pad_i,dcd_pad_i};
+
+assign                  {cts_c, dsr_c, ri_c, dcd_c} = loopback ? {mcr[`UART_MC_RTS],mcr[`UART_MC_DTR],mcr[`UART_MC_OUT1],mcr[`UART_MC_OUT2]}
+                                                               : {cts_pad_i,dsr_pad_i,ri_pad_i,dcd_pad_i};
+
+assign 									dlab = lcr[`UART_LC_DL];
+assign 									loopback = mcr[4];
+
+// assign modem outputs
+assign 									rts_pad_o = mcr[`UART_MC_RTS];
+assign 									dtr_pad_o = mcr[`UART_MC_DTR];
+
+// Interrupt signals
+wire 										rls_int;  // receiver line status interrupt
+wire 										rda_int;  // receiver data available interrupt
+wire 										ti_int;   // timeout indicator interrupt
+wire										thre_int; // transmitter holding register empty interrupt
+wire 										ms_int;   // modem status interrupt
+
+// FIFO signals
+reg 										tf_push;
+reg 										rf_pop;
+wire [`UART_FIFO_REC_WIDTH-1:0] 	rf_data_out;
+wire 										rf_error_bit; // an error (parity or framing) is inside the fifo
+wire 					rf_overrun;
+wire 					rf_push_pulse;
+wire [`UART_FIFO_COUNTER_W-1:0] 	rf_count;
+wire [`UART_FIFO_COUNTER_W-1:0] 	tf_count;
+wire [2:0] 								tstate;
+wire [3:0] 								rstate;
+wire [9:0] 								counter_t;
+
+wire                      thre_set_en; // THRE status is delayed one character time when a character is written to fifo.
+reg  [7:0]                block_cnt;   // While counter counts, THRE status is blocked (delayed one character cycle)
+reg  [7:0]                block_value; // One character length minus stop bit
+
+// Transmitter Instance
+wire serial_out;
+
+uart_transmitter #(.SIM (SIM)) transmitter(clk, wb_rst_i, lcr, tf_push, wb_dat_i, enable, serial_out, tstate, tf_count, tx_reset, lsr_mask);
+
+  // Synchronizing and sampling serial RX input
+  uart_sync_flops    i_uart_sync_flops
+  (
+    .rst_i           (wb_rst_i),
+    .clk_i           (clk),
+    .stage1_rst_i    (1'b0),
+    .stage1_clk_en_i (1'b1),
+    .async_dat_i     (srx_pad_i),
+    .sync_dat_o      (srx_pad)
+  );
+  defparam i_uart_sync_flops.width      = 1;
+  defparam i_uart_sync_flops.init_value = 1'b1;
+
+// handle loopback
+wire serial_in = loopback ? serial_out : srx_pad;
+assign stx_pad_o = loopback ? 1'b1 : serial_out;
+
+// Receiver Instance
+uart_receiver receiver(clk, wb_rst_i, lcr, rf_pop, serial_in, enable, 
+	counter_t, rf_count, rf_data_out, rf_error_bit, rf_overrun, rx_reset, lsr_mask, rstate, rf_push_pulse);
+
+
+// Asynchronous reading here because the outputs are sampled in uart_wb.v file 
+always @(dl or dlab or ier or iir or scratch
+			or lcr or lsr or msr or rf_data_out or wb_addr_i or wb_re_i)   // asynchrounous reading
+begin
+	case (wb_addr_i)
+		`UART_REG_RB   : wb_dat_o = dlab ? dl[`UART_DL1] : rf_data_out[10:3];
+		`UART_REG_IE	: wb_dat_o = dlab ? dl[`UART_DL2] : {4'd0,ier};
+		`UART_REG_II	: wb_dat_o = {4'b1100,iir};
+		`UART_REG_LC	: wb_dat_o = lcr;
+		`UART_REG_LS	: wb_dat_o = lsr;
+		`UART_REG_MS	: wb_dat_o = msr;
+		`UART_REG_SR	: wb_dat_o = scratch;
+		default:  wb_dat_o = 8'b0; // ??
+	endcase // case(wb_addr_i)
+end // always @ (dl or dlab or ier or iir or scratch...
+
+
+// rf_pop signal handling
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		rf_pop <= 0;
+	else
+	if (rf_pop)	// restore the signal to 0 after one clock cycle
+		rf_pop <= 0;
+	else
+	if (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab)
+		rf_pop <= 1; // advance read pointer
+end
+
+wire 	lsr_mask_condition;
+wire 	iir_read;
+wire  msr_read;
+wire	fifo_read;
+wire	fifo_write;
+
+assign lsr_mask_condition = (wb_re_i && wb_addr_i == `UART_REG_LS && !dlab);
+assign iir_read = (wb_re_i && wb_addr_i == `UART_REG_II && !dlab);
+assign msr_read = (wb_re_i && wb_addr_i == `UART_REG_MS && !dlab);
+assign fifo_read = (wb_re_i && wb_addr_i == `UART_REG_RB && !dlab);
+assign fifo_write = (wb_we_i && wb_addr_i == `UART_REG_TR && !dlab);
+
+// lsr_mask_d delayed signal handling
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		lsr_mask_d <= 0;
+	else // reset bits in the Line Status Register
+		lsr_mask_d <= lsr_mask_condition;
+end
+
+// lsr_mask is rise detected
+assign lsr_mask = lsr_mask_condition && ~lsr_mask_d;
+
+// msi_reset signal handling
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		msi_reset <= 1;
+	else
+	if (msi_reset)
+		msi_reset <= 0;
+	else
+	if (msr_read)
+		msi_reset <= 1; // reset bits in Modem Status Register
+end
+
+
+//
+//   WRITES AND RESETS   //
+//
+// Line Control Register
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i)
+		lcr <= 8'b00000011; // 8n1 setting
+	else
+	if (wb_we_i && wb_addr_i==`UART_REG_LC)
+		lcr <= wb_dat_i;
+
+// Interrupt Enable Register or UART_DL2
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i)
+	begin
+		ier <= 4'b0000; // no interrupts after reset
+`ifdef PRESCALER_PRESET_HARD
+		dl[`UART_DL2] <= `PRESCALER_HIGH_PRESET;
+`else
+		dl[`UART_DL2] <= 8'b0;
+`endif
+	end
+	else
+	if (wb_we_i && wb_addr_i==`UART_REG_IE)
+		if (dlab)
+		begin
+			dl[`UART_DL2] <=
+`ifdef PRESCALER_PRESET_HARD
+			dl[`UART_DL2];
+`else
+		   wb_dat_i;
+`endif
+		end
+		else
+			ier <= wb_dat_i[3:0]; // ier uses only 4 lsb
+
+
+// FIFO Control Register and rx_reset, tx_reset signals
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) begin
+		fcr <= 2'b11;
+		rx_reset <= 0;
+		tx_reset <= 0;
+	end else
+	if (wb_we_i && wb_addr_i==`UART_REG_FC) begin
+		fcr <= wb_dat_i[7:6];
+		rx_reset <= wb_dat_i[1];
+		tx_reset <= wb_dat_i[2];
+	end else begin
+		rx_reset <= 0;
+		tx_reset <= 0;
+	end
+
+// Modem Control Register
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i)
+		mcr <= 5'b0;
+	else
+	if (wb_we_i && wb_addr_i==`UART_REG_MC)
+			mcr <= wb_dat_i[4:0];
+
+// Scratch register
+// Line Control Register
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i)
+		scratch <= 0; // 8n1 setting
+	else
+	if (wb_we_i && wb_addr_i==`UART_REG_SR)
+		scratch <= wb_dat_i;
+
+// TX_FIFO or UART_DL1
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i)
+	begin
+`ifdef PRESCALER_PRESET_HARD
+		dl[`UART_DL1]  <= `PRESCALER_LOW_PRESET;
+`else
+		dl[`UART_DL1]  <= 8'b0;
+`endif
+		tf_push   <= 1'b0;
+		start_dlc <= 1'b0;
+	end
+	else
+	if (wb_we_i && wb_addr_i==`UART_REG_TR)
+		if (dlab)
+		begin
+`ifdef PRESCALER_PRESET_HARD
+			dl[`UART_DL1] <= dl[`UART_DL1];
+`else
+			dl[`UART_DL1] <= wb_dat_i;
+`endif
+			start_dlc <= 1'b1; // enable DL counter
+			tf_push <= 1'b0;
+		end
+		else
+		begin
+			tf_push   <= 1'b1;
+			start_dlc <= 1'b0;
+		end // else: !if(dlab)
+	else
+	begin
+		start_dlc <= 1'b0;
+		tf_push   <= 1'b0;
+	end // else: !if(dlab)
+
+// Receiver FIFO trigger level selection logic (asynchronous mux)
+always @(fcr)
+	case (fcr[`UART_FC_TL])
+		2'b00 : trigger_level = 1;
+		2'b01 : trigger_level = 4;
+		2'b10 : trigger_level = 8;
+		2'b11 : trigger_level = 14;
+	endcase // case(fcr[`UART_FC_TL])
+	
+//
+//  STATUS REGISTERS  //
+//
+
+// Modem Status Register
+reg [3:0] delayed_modem_signals;
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+	  begin
+  		msr <= 0;
+	  	delayed_modem_signals[3:0] <= 0;
+	  end
+	else begin
+		msr[`UART_MS_DDCD:`UART_MS_DCTS] <= msi_reset ? 4'b0 :
+			msr[`UART_MS_DDCD:`UART_MS_DCTS] | ({dcd, ri, dsr, cts} ^ delayed_modem_signals[3:0]);
+		msr[`UART_MS_CDCD:`UART_MS_CCTS] <= {dcd_c, ri_c, dsr_c, cts_c};
+		delayed_modem_signals[3:0] <= {dcd, ri, dsr, cts};
+	end
+end
+
+
+// Line Status Register
+
+// activation conditions
+assign lsr0 = (rf_count==0 && rf_push_pulse);  // data in receiver fifo available set condition
+assign lsr1 = rf_overrun;     // Receiver overrun error
+assign lsr2 = rf_data_out[1]; // parity error bit
+assign lsr3 = rf_data_out[0]; // framing error bit
+assign lsr4 = rf_data_out[2]; // break error in the character
+assign lsr5 = (tf_count==5'b0 && thre_set_en);  // transmitter fifo is empty
+assign lsr6 = (tf_count==5'b0 && thre_set_en && (tstate == /*`S_IDLE */ 0)); // transmitter empty
+assign lsr7 = rf_error_bit | rf_overrun;
+
+// lsr bit0 (receiver data available)
+reg 	 lsr0_d;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr0_d <= 0;
+	else lsr0_d <= lsr0;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr0r <= 0;
+	else lsr0r <= (rf_count==1 && rf_pop && !rf_push_pulse || rx_reset) ? 1'b0 : // deassert condition
+					  lsr0r || (lsr0 && ~lsr0_d); // set on rise of lsr0 and keep asserted until deasserted 
+
+// lsr bit 1 (receiver overrun)
+reg lsr1_d; // delayed
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr1_d <= 0;
+	else lsr1_d <= lsr1;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr1r <= 0;
+	else	lsr1r <= lsr_mask ? 1'b0 : lsr1r || (lsr1 && ~lsr1_d); // set on rise
+
+// lsr bit 2 (parity error)
+reg lsr2_d; // delayed
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr2_d <= 0;
+	else lsr2_d <= lsr2;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr2r <= 0;
+	else lsr2r <= lsr_mask ? 1'b0 : lsr2r || (lsr2 && ~lsr2_d); // set on rise
+
+// lsr bit 3 (framing error)
+reg lsr3_d; // delayed
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr3_d <= 0;
+	else lsr3_d <= lsr3;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr3r <= 0;
+	else lsr3r <= lsr_mask ? 1'b0 : lsr3r || (lsr3 && ~lsr3_d); // set on rise
+
+// lsr bit 4 (break indicator)
+reg lsr4_d; // delayed
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr4_d <= 0;
+	else lsr4_d <= lsr4;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr4r <= 0;
+	else lsr4r <= lsr_mask ? 1'b0 : lsr4r || (lsr4 && ~lsr4_d);
+
+// lsr bit 5 (transmitter fifo is empty)
+reg lsr5_d;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr5_d <= 1;
+	else lsr5_d <= lsr5;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr5r <= 1;
+	else lsr5r <= (fifo_write) ? 1'b0 :  lsr5r || (lsr5 && ~lsr5_d);
+
+// lsr bit 6 (transmitter empty indicator)
+reg lsr6_d;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr6_d <= 1;
+	else lsr6_d <= lsr6;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr6r <= 1;
+	else lsr6r <= (fifo_write) ? 1'b0 : lsr6r || (lsr6 && ~lsr6_d);
+
+// lsr bit 7 (error in fifo)
+reg lsr7_d;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr7_d <= 0;
+	else lsr7_d <= lsr7;
+
+always @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) lsr7r <= 0;
+	else lsr7r <= lsr_mask ? 1'b0 : lsr7r || (lsr7 && ~lsr7_d);
+
+// Frequency divider
+always @(posedge clk or posedge wb_rst_i) 
+begin
+	if (wb_rst_i)
+		dlc <= 0;
+	else
+		if (start_dlc | ~ (|dlc))
+  			dlc <= dl - 16'd1;               // preset counter
+		else
+			dlc <= dlc - 16'd1;              // decrement counter
+end
+
+// Enable signal generation logic
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		enable <= 1'b0;
+	else
+		if (|dl & ~(|dlc))     // dl>0 & dlc==0
+			enable <= 1'b1;
+		else
+			enable <= 1'b0;
+end
+
+// Delaying THRE status for one character cycle after a character is written to an empty fifo.
+always @(lcr)
+  case (lcr[3:0])
+    4'b0000                             : block_value =  95; // 6 bits
+    4'b0100                             : block_value = 103; // 6.5 bits
+    4'b0001, 4'b1000                    : block_value = 111; // 7 bits
+    4'b1100                             : block_value = 119; // 7.5 bits
+    4'b0010, 4'b0101, 4'b1001           : block_value = 127; // 8 bits
+    4'b0011, 4'b0110, 4'b1010, 4'b1101  : block_value = 143; // 9 bits
+    4'b0111, 4'b1011, 4'b1110           : block_value = 159; // 10 bits
+    4'b1111                             : block_value = 175; // 11 bits
+  endcase // case(lcr[3:0])
+
+// Counting time of one character minus stop bit
+always @(posedge clk or posedge wb_rst_i)
+begin
+  if (wb_rst_i)
+    block_cnt <= 8'd0;
+  else
+  if(lsr5r & fifo_write)  // THRE bit set & write to fifo occured
+    block_cnt <= SIM ? 8'd1 : block_value;
+  else
+  if (enable & block_cnt != 8'b0)  // only work on enable times
+    block_cnt <= block_cnt - 8'd1;  // decrement break counter
+end // always of break condition detection
+
+// Generating THRE status enable signal
+assign thre_set_en = ~(|block_cnt);
+
+
+//
+//	INTERRUPT LOGIC
+//
+
+assign rls_int  = ier[`UART_IE_RLS] && (lsr[`UART_LS_OE] || lsr[`UART_LS_PE] || lsr[`UART_LS_FE] || lsr[`UART_LS_BI]);
+assign rda_int  = ier[`UART_IE_RDA] && (rf_count >= {1'b0,trigger_level});
+assign thre_int = ier[`UART_IE_THRE] && lsr[`UART_LS_TFE];
+assign ms_int   = ier[`UART_IE_MS] && (| msr[3:0]);
+assign ti_int   = ier[`UART_IE_RDA] && (counter_t == 10'b0) && (|rf_count);
+
+reg 	 rls_int_d;
+reg 	 thre_int_d;
+reg 	 ms_int_d;
+reg 	 ti_int_d;
+reg 	 rda_int_d;
+
+// delay lines
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) rls_int_d <= 0;
+	else rls_int_d <= rls_int;
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) rda_int_d <= 0;
+	else rda_int_d <= rda_int;
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) thre_int_d <= 0;
+	else thre_int_d <= thre_int;
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) ms_int_d <= 0;
+	else ms_int_d <= ms_int;
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) ti_int_d <= 0;
+	else ti_int_d <= ti_int;
+
+// rise detection signals
+
+wire 	 rls_int_rise;
+wire 	 thre_int_rise;
+wire 	 ms_int_rise;
+wire 	 ti_int_rise;
+wire 	 rda_int_rise;
+
+assign rda_int_rise    = rda_int & ~rda_int_d;
+assign rls_int_rise 	  = rls_int & ~rls_int_d;
+assign thre_int_rise   = thre_int & ~thre_int_d;
+assign ms_int_rise 	  = ms_int & ~ms_int_d;
+assign ti_int_rise 	  = ti_int & ~ti_int_d;
+
+// interrupt pending flags
+reg 	rls_int_pnd;
+reg	rda_int_pnd;
+reg 	thre_int_pnd;
+reg 	ms_int_pnd;
+reg 	ti_int_pnd;
+
+// interrupt pending flags assignments
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) rls_int_pnd <= 0;
+	else 
+		rls_int_pnd <= lsr_mask ? 1'b0 :  						// reset condition
+							rls_int_rise ? 1'b1 :						// latch condition
+							rls_int_pnd && ier[`UART_IE_RLS];	// default operation: remove if masked
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) rda_int_pnd <= 0;
+	else 
+		rda_int_pnd <= ((rf_count == {1'b0,trigger_level}) && fifo_read) ? 1'b0 :  	// reset condition
+							rda_int_rise ? 1'b1 :						// latch condition
+							rda_int_pnd && ier[`UART_IE_RDA];	// default operation: remove if masked
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) thre_int_pnd <= 0;
+	else 
+		thre_int_pnd <= fifo_write || (iir_read & ~iir[`UART_II_IP] & iir[`UART_II_II] == `UART_II_THRE)? 1'b0 :
+							thre_int_rise ? 1'b1 :
+							thre_int_pnd && ier[`UART_IE_THRE];
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) ms_int_pnd <= 0;
+	else 
+		ms_int_pnd <= msr_read ? 1'b0 :
+							ms_int_rise ? 1'b1 :
+							ms_int_pnd && ier[`UART_IE_MS];
+
+always  @(posedge clk or posedge wb_rst_i)
+	if (wb_rst_i) ti_int_pnd <= 0;
+	else 
+		ti_int_pnd <= fifo_read ? 1'b0 :
+							ti_int_rise ? 1'b1 :
+							ti_int_pnd && ier[`UART_IE_RDA];
+// end of pending flags
+
+// INT_O logic
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)	
+		int_o <= 1'b0;
+	else
+		int_o <=
+					rls_int_pnd		?	~lsr_mask					:
+					rda_int_pnd		? 1'b1								:
+					ti_int_pnd		? ~fifo_read					:
+					thre_int_pnd	? !(fifo_write & iir_read) :
+					ms_int_pnd		? ~msr_read						:
+					1'd0;	// if no interrupt are pending
+end
+
+
+// Interrupt Identification register
+always @(posedge clk or posedge wb_rst_i)
+begin
+	if (wb_rst_i)
+		iir <= 1;
+	else
+	if (rls_int_pnd)  // interrupt is pending
+	begin
+		iir[`UART_II_II] <= `UART_II_RLS;	// set identification register to correct value
+		iir[`UART_II_IP] <= 1'b0;		// and clear the IIR bit 0 (interrupt pending)
+	end else // the sequence of conditions determines priority of interrupt identification
+	if (rda_int)
+	begin
+		iir[`UART_II_II] <= `UART_II_RDA;
+		iir[`UART_II_IP] <= 1'b0;
+	end
+	else if (ti_int_pnd)
+	begin
+		iir[`UART_II_II] <= `UART_II_TI;
+		iir[`UART_II_IP] <= 1'b0;
+	end
+	else if (thre_int_pnd)
+	begin
+		iir[`UART_II_II] <= `UART_II_THRE;
+		iir[`UART_II_IP] <= 1'b0;
+	end
+	else if (ms_int_pnd)
+	begin
+		iir[`UART_II_II] <= `UART_II_MS;
+		iir[`UART_II_IP] <= 1'b0;
+	end else	// no interrupt is pending
+	begin
+		iir[`UART_II_II] <= 0;
+		iir[`UART_II_IP] <= 1'b1;
+	end
+end
+
+endmodule

uart16550/uart_rfifo.v

@@ -0,0 +1,316 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_rfifo.v (Modified from uart_fifo.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 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: not supported by cvs2svn $
+// Revision 1.3  2003/06/11 16:37:47  gorban
+// This fixes errors in some cases when data is being read and put to the FIFO at the same time. Patch is submitted by Scott Furman. Update is very recommended.
+//
+// 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
+//
+//
+
+`include "uart_defines.v"
+
+module uart_rfifo (clk, 
+	wb_rst_i, data_in, data_out,
+// Control signals
+	push, // push strobe, active high
+	pop,   // pop strobe, active high
+// status signals
+	overrun,
+	count,
+	error_bit,
+	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;
+output				error_bit;
+
+wire	[fifo_width-1:0]	data_out;
+wire [7:0] data8_out;
+// flags FIFO
+reg	[2:0]	fifo[fifo_depth-1:0];
+
+// 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 + 4'h1;
+
+raminfr #(fifo_pointer_w,8,fifo_depth) rfifo  
+        (.clk(clk), 
+			.we(push), 
+			.a(top), 
+			.dpra(bottom), 
+			.di(data_in[fifo_width-1:fifo_width-8]), 
+			.dpo(data8_out)
+		); 
+
+always @(posedge clk or posedge wb_rst_i) // synchronous FIFO
+begin
+	if (wb_rst_i)
+	begin
+		top		<= 0;
+		bottom		<= 0;
+		count		<= 0;
+		fifo[0] <= 0;
+		fifo[1] <= 0;
+		fifo[2] <= 0;
+		fifo[3] <= 0;
+		fifo[4] <= 0;
+		fifo[5] <= 0;
+		fifo[6] <= 0;
+		fifo[7] <= 0;
+		fifo[8] <= 0;
+		fifo[9] <= 0;
+		fifo[10] <= 0;
+		fifo[11] <= 0;
+		fifo[12] <= 0;
+		fifo[13] <= 0;
+		fifo[14] <= 0;
+		fifo[15] <= 0;
+	end
+	else
+	if (fifo_reset) begin
+		top		<= 0;
+		bottom		<= 0;
+		count		<= 0;
+		fifo[0] <= 0;
+		fifo[1] <= 0;
+		fifo[2] <= 0;
+		fifo[3] <= 0;
+		fifo[4] <= 0;
+		fifo[5] <= 0;
+		fifo[6] <= 0;
+		fifo[7] <= 0;
+		fifo[8] <= 0;
+		fifo[9] <= 0;
+		fifo[10] <= 0;
+		fifo[11] <= 0;
+		fifo[12] <= 0;
+		fifo[13] <= 0;
+		fifo[14] <= 0;
+		fifo[15] <= 0;
+	end
+  else
+	begin
+		case ({push, pop})
+		2'b10 : if (count<fifo_depth)  // overrun condition
+			begin
+				top       <= top_plus_1;
+				fifo[top] <= data_in[2:0];
+				count     <= count + 5'd1;
+			end
+		2'b01 : if(count>0)
+			begin
+        fifo[bottom] <= 0;
+				bottom   <= bottom + 4'd1;
+				count	 <= count - 5'd1;
+			end
+		2'b11 : begin
+				bottom   <= bottom + 4'd1;
+				top       <= top_plus_1;
+				fifo[top] <= data_in[2:0];
+		        end
+    default: ;
+		endcase
+	end
+end   // always
+
+always @(posedge clk or posedge wb_rst_i) // synchronous FIFO
+begin
+  if (wb_rst_i)
+    overrun   <= 1'b0;
+  else
+  if(fifo_reset | reset_status) 
+    overrun   <= 1'b0;
+  else
+  if(push & ~pop & (count==fifo_depth))
+    overrun   <= 1'b1;
+end   // always
+
+
+// please note though that data_out is only valid one clock after pop signal
+assign data_out = {data8_out,fifo[bottom]};
+
+// Additional logic for detection of error conditions (parity and framing) inside the FIFO
+// for the Line Status Register bit 7
+
+wire	[2:0]	word0 = fifo[0];
+wire	[2:0]	word1 = fifo[1];
+wire	[2:0]	word2 = fifo[2];
+wire	[2:0]	word3 = fifo[3];
+wire	[2:0]	word4 = fifo[4];
+wire	[2:0]	word5 = fifo[5];
+wire	[2:0]	word6 = fifo[6];
+wire	[2:0]	word7 = fifo[7];
+
+wire	[2:0]	word8 = fifo[8];
+wire	[2:0]	word9 = fifo[9];
+wire	[2:0]	word10 = fifo[10];
+wire	[2:0]	word11 = fifo[11];
+wire	[2:0]	word12 = fifo[12];
+wire	[2:0]	word13 = fifo[13];
+wire	[2:0]	word14 = fifo[14];
+wire	[2:0]	word15 = fifo[15];
+
+// a 1 is returned if any of the error bits in the fifo is 1
+assign	error_bit = |(word0[2:0]  | word1[2:0]  | word2[2:0]  | word3[2:0]  |
+            		      word4[2:0]  | word5[2:0]  | word6[2:0]  | word7[2:0]  |
+            		      word8[2:0]  | word9[2:0]  | word10[2:0] | word11[2:0] |
+            		      word12[2:0] | word13[2:0] | word14[2:0] | word15[2:0] );
+
+endmodule

uart16550/uart_sync_flops.v

@@ -0,0 +1,117 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_sync_flops.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):                                                  ////
+////      - Andrej Erzen (andreje@flextronics.si)                 ////
+////      - Tadej Markovic (tadejm@flextronics.si)                ////
+////                                                              ////
+////  Created:        2004/05/20                                  ////
+////  Last Updated:   2004/05/20                                  ////
+////                  (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 $
+//
+
+module uart_sync_flops
+(
+  // internal signals
+  rst_i,
+  clk_i,
+  stage1_rst_i,
+  stage1_clk_en_i,
+  async_dat_i,
+  sync_dat_o
+);
+
+parameter width         = 1;
+parameter init_value    = 1'b0;
+
+input                           rst_i;                  // reset input
+input                           clk_i;                  // clock input
+input                           stage1_rst_i;           // synchronous reset for stage 1 FF
+input                           stage1_clk_en_i;        // synchronous clock enable for stage 1 FF
+input   [width-1:0]             async_dat_i;            // asynchronous data input
+output  [width-1:0]             sync_dat_o;             // synchronous data output
+
+
+//
+// Interal signal declarations
+//
+
+reg     [width-1:0]             sync_dat_o;
+reg     [width-1:0]             flop_0;
+
+
+// first stage
+always @ (posedge clk_i or posedge rst_i)
+begin
+    if (rst_i)
+        flop_0 <= {width{init_value}};
+    else
+        flop_0 <= async_dat_i;    
+end
+
+// second stage
+always @ (posedge clk_i or posedge rst_i)
+begin
+    if (rst_i)
+        sync_dat_o <= {width{init_value}};
+    else if (stage1_rst_i)
+        sync_dat_o <= {width{init_value}};
+    else if (stage1_clk_en_i)
+        sync_dat_o <= flop_0;       
+end
+
+endmodule

uart16550/uart_tfifo.v

@@ -0,0 +1,239 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  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: not supported by cvs2svn $
+// 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
+//
+//
+
+`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 + 4'd1;
+
+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		<= 0;
+		bottom		<= 0;
+		count		<= 0;
+	end
+	else
+	if (fifo_reset) begin
+		top		<= 0;
+		bottom		<= 0;
+		count		<= 0;
+	end
+  else
+	begin
+		case ({push, pop})
+		2'b10 : if (count<fifo_depth)  // overrun condition
+			begin
+				top       <= top_plus_1;
+				count     <= count + 5'd1;
+			end
+		2'b01 : if(count>0)
+			begin
+				bottom   <= bottom + 4'd1;
+				count	 <= count - 5'd1;
+			end
+		2'b11 : begin
+				bottom   <= bottom + 4'd1;
+				top       <= 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'b0;
+  else
+  if(fifo_reset | reset_status) 
+    overrun   <= 1'b0;
+  else
+  if(push & (count==fifo_depth))
+    overrun   <= 1'b1;
+end   // always
+
+endmodule

uart16550/uart_top.v

@@ -0,0 +1,261 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_top.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 top level.                                        ////
+////                                                              ////
+////  Known problems (limits):                                    ////
+////  Note that transmitter and receiver instances are inside     ////
+////  the uart_regs.v file.                                       ////
+////                                                              ////
+////  To Do:                                                      ////
+////  Nothing so far.                                             ////
+////                                                              ////
+////  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 1.18  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 1.17  2001/12/19 08:40:03  mohor
+// Warnings fixed (unused signals removed).
+//
+// Revision 1.16  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 1.15  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 1.14  2001/11/07 17:51:52  gorban
+// Heavily rewritten interrupt and LSR subsystems.
+// Many bugs hopefully squashed.
+//
+// Revision 1.13  2001/10/20 09:58:40  gorban
+// Small synopsis fixes
+//
+// Revision 1.12  2001/08/25 15:46:19  gorban
+// Modified port names again
+//
+// Revision 1.11  2001/08/24 21:01:12  mohor
+// Things connected to parity changed.
+// Clock devider changed.
+//
+// Revision 1.10  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 19:12:02  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 21:27:12+02  jacob
+// Initial revision
+//
+//
+
+`include "uart_defines.v"
+
+module uart_top	(
+	wb_clk_i, 
+	
+	// Wishbone signals
+	wb_rst_i, wb_adr_i, wb_dat_i, wb_dat_o, wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o, wb_sel_i,
+	int_o, // interrupt request
+
+	// UART	signals
+	// serial input/output
+	stx_pad_o, srx_pad_i,
+
+	// modem signals
+	rts_pad_o, cts_pad_i, dtr_pad_o, dsr_pad_i, ri_pad_i, dcd_pad_i
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+	, baud_o
+`endif
+	);
+parameter SIM = 0;
+parameter debug = 0;
+
+input 								 wb_clk_i;
+
+// WISHBONE interface
+input 								 wb_rst_i;
+input [2:0] 	 wb_adr_i;
+input [7:0] 	 wb_dat_i;
+output [7:0] 	 wb_dat_o;
+input 								 wb_we_i;
+input 								 wb_stb_i;
+input 								 wb_cyc_i;
+input [3:0]							 wb_sel_i;
+output 								 wb_ack_o;
+output 								 int_o;
+
+// UART	signals
+input 								 srx_pad_i;
+output 								 stx_pad_o;
+output 								 rts_pad_o;
+input 								 cts_pad_i;
+output 								 dtr_pad_o;
+input 								 dsr_pad_i;
+input 								 ri_pad_i;
+input 								 dcd_pad_i;
+
+// optional baudrate output
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+output	baud_o;
+`endif
+
+
+wire 									 stx_pad_o;
+wire 									 rts_pad_o;
+wire 									 dtr_pad_o;
+
+wire [2:0] 	 wb_adr_i;
+wire [7:0] 	 wb_dat_i;
+wire [7:0] 	 wb_dat_o;
+
+wire [7:0] 							 wb_dat8_i; // 8-bit internal data input
+wire [7:0] 							 wb_dat8_o; // 8-bit internal data output
+wire [31:0] 						 wb_dat32_o; // debug interface 32-bit output
+wire [3:0] 							 wb_sel_i;  // WISHBONE select signal
+wire [2:0] 	 wb_adr_int;
+wire 									 we_o;	// Write enable for registers
+wire		          	     re_o;	// Read enable for registers
+//
+// MODULE INSTANCES
+//
+
+////  WISHBONE interface module
+uart_wb		wb_interface(
+		.clk(		wb_clk_i		),
+		.wb_rst_i(	wb_rst_i	),
+	.wb_dat_i(wb_dat_i),
+	.wb_dat_o(wb_dat_o),
+	.wb_dat8_i(wb_dat8_i),
+	.wb_dat8_o(wb_dat8_o),
+	 .wb_dat32_o(32'b0),								 
+	 .wb_sel_i(4'b0),
+		.wb_we_i(	wb_we_i		),
+		.wb_stb_i(	wb_stb_i	),
+		.wb_cyc_i(	wb_cyc_i	),
+		.wb_ack_o(	wb_ack_o	),
+	.wb_adr_i(wb_adr_i),
+	.wb_adr_int(wb_adr_int),
+		.we_o(		we_o		),
+		.re_o(re_o)
+		);
+
+// Registers
+uart_regs #(.SIM (SIM))	regs(
+	.clk(		wb_clk_i		),
+	.wb_rst_i(	wb_rst_i	),
+	.wb_addr_i(	wb_adr_int	),
+	.wb_dat_i(	wb_dat8_i	),
+	.wb_dat_o(	wb_dat8_o	),
+	.wb_we_i(	we_o		),
+   .wb_re_i(re_o),
+	.modem_inputs(	{cts_pad_i, dsr_pad_i,
+	ri_pad_i,  dcd_pad_i}	),
+	.stx_pad_o(		stx_pad_o		),
+	.srx_pad_i(		srx_pad_i		),
+	.rts_pad_o(		rts_pad_o		),
+	.dtr_pad_o(		dtr_pad_o		),
+	.int_o(		int_o		)
+`ifdef UART_HAS_BAUDRATE_OUTPUT
+	, .baud_o(baud_o)
+`endif
+
+);
+
+initial
+begin
+   if(debug) begin
+	`ifdef UART_HAS_BAUDRATE_OUTPUT
+		$display("(%m) UART INFO: Has baudrate output\n");
+	`else
+		$display("(%m) UART INFO: Doesn't have baudrate output\n");
+	`endif
+   end
+end
+
+endmodule
+
+

uart16550/uart_transmitter.v

@@ -0,0 +1,354 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  uart_transmitter.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 logic                                 ////
+////                                                              ////
+////  Known problems (limits):                                    ////
+////  None known                                                  ////
+////                                                              ////
+////  To Do:                                                      ////
+////  Thourough testing.                                          ////
+////                                                              ////
+////  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 1.18  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  2002/01/08 11:29:40  mohor
+// tf_pop was too wide. Now it is only 1 clk cycle width.
+//
+// Revision 1.15  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 1.14  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 1.13  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  2001/10/29 17:00:46  gorban
+// fixed parity sending and tx_fifo resets over- and underrun
+//
+// 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 21:27:12+02  jacob
+// Initial revision
+//
+//
+
+`include "uart_defines.v"
+
+module uart_transmitter
+#(parameter SIM = 0)
+ (clk, wb_rst_i, lcr, tf_push, wb_dat_i, enable,	stx_pad_o, tstate, tf_count, tx_reset, lsr_mask);
+
+input 										clk;
+input 										wb_rst_i;
+input [7:0] 								lcr;
+input 										tf_push;
+input [7:0] 								wb_dat_i;
+input 										enable;
+input 										tx_reset;
+input 										lsr_mask; //reset of fifo
+output 										stx_pad_o;
+output [2:0] 								tstate;
+output [`UART_FIFO_COUNTER_W-1:0] 	tf_count;
+
+reg [2:0] 									tstate;
+reg [4:0] 									counter;
+reg [2:0] 									bit_counter;   // counts the bits to be sent
+reg [6:0] 									shift_out;	// output shift register
+reg 											stx_o_tmp;
+reg 											parity_xor;  // parity of the word
+reg 											tf_pop;
+reg 											bit_out;
+
+// TX FIFO instance
+//
+// Transmitter FIFO signals
+wire [`UART_FIFO_WIDTH-1:0] 			tf_data_in;
+wire [`UART_FIFO_WIDTH-1:0] 			tf_data_out;
+wire 											tf_push;
+wire 											tf_overrun;
+wire [`UART_FIFO_COUNTER_W-1:0] 		tf_count;
+
+assign 										tf_data_in = wb_dat_i;
+
+uart_tfifo fifo_tx(	// error bit signal is not used in transmitter FIFO
+	.clk(		clk		), 
+	.wb_rst_i(	wb_rst_i	),
+	.data_in(	tf_data_in	),
+	.data_out(	tf_data_out	),
+	.push(		tf_push		),
+	.pop(		tf_pop		),
+	.overrun(	tf_overrun	),
+	.count(		tf_count	),
+	.fifo_reset(	tx_reset	),
+	.reset_status(lsr_mask)
+);
+
+// TRANSMITTER FINAL STATE MACHINE
+
+localparam s_idle        = 3'd0;
+localparam s_send_start  = 3'd1;
+localparam s_send_byte   = 3'd2;
+localparam s_send_parity = 3'd3;
+localparam s_send_stop   = 3'd4;
+localparam s_pop_byte    = 3'd5;
+
+always @(posedge clk or posedge wb_rst_i)
+begin
+  if (wb_rst_i)
+  begin
+	tstate       <= s_idle;
+	stx_o_tmp       <= 1'b1;
+	counter   <= 5'b0;
+	shift_out   <= 7'b0;
+	bit_out     <= 1'b0;
+	parity_xor  <= 1'b0;
+	tf_pop      <= 1'b0;
+	bit_counter <= 3'b0;
+  end
+  else
+  if (enable | SIM)
+  begin
+	case (tstate)
+	s_idle	 :	if (~|tf_count) // if tf_count==0
+			begin
+				tstate <= s_idle;
+				stx_o_tmp <= 1'b1;
+			end
+			else
+			begin
+				tf_pop <= 1'b0;
+				stx_o_tmp  <= 1'b1;
+				tstate  <= s_pop_byte;
+			end
+	s_pop_byte :	begin
+				tf_pop <= 1'b1;
+				case (lcr[/*`UART_LC_BITS*/1:0])  // number of bits in a word
+				2'b00 : begin
+					bit_counter <= 3'b100;
+					parity_xor  <= ^tf_data_out[4:0];
+				     end
+				2'b01 : begin
+					bit_counter <= 3'b101;
+					parity_xor  <= ^tf_data_out[5:0];
+				     end
+				2'b10 : begin
+					bit_counter <= 3'b110;
+					parity_xor  <= ^tf_data_out[6:0];
+				     end
+				2'b11 : begin
+					bit_counter <= 3'b111;
+					parity_xor  <= ^tf_data_out[7:0];
+				     end
+				endcase
+				{shift_out[6:0], bit_out} <= tf_data_out;
+				tstate <= s_send_start;
+			end
+	s_send_start :	begin
+				tf_pop <= 1'b0;
+				if (~|counter)
+					counter <= 5'b01111;
+				else
+				if (counter == 5'b00001)
+				begin
+					counter <= 0;
+					tstate <= s_send_byte;
+				end
+				else
+					counter <= counter - 5'd1;
+				stx_o_tmp <= 1'b0;
+				if (SIM) begin
+					tstate <= s_idle;
+					$write("%c", tf_data_out);
+					$fflush(32'h80000001);
+				end
+			end
+	s_send_byte :	begin
+				if (~|counter)
+					counter <= 5'b01111;
+				else
+				if (counter == 5'b00001)
+				begin
+					if (bit_counter > 3'b0)
+					begin
+						bit_counter <= bit_counter - 3'd1;
+						{shift_out[5:0],bit_out  } <= {shift_out[6:1], shift_out[0]};
+						tstate <= s_send_byte;
+					end
+					else   // end of byte
+					if (~lcr[`UART_LC_PE])
+					begin
+						tstate <= s_send_stop;
+					end
+					else
+					begin
+						case ({lcr[`UART_LC_EP],lcr[`UART_LC_SP]})
+						2'b00:	bit_out <= ~parity_xor;
+						2'b01:	bit_out <= 1'b1;
+						2'b10:	bit_out <= parity_xor;
+						2'b11:	bit_out <= 1'b0;
+						endcase
+						tstate <= s_send_parity;
+					end
+					counter <= 0;
+				end
+				else
+					counter <= counter - 5'd1;
+				stx_o_tmp <= bit_out; // set output pin
+			end
+	s_send_parity :	begin
+				if (~|counter)
+					counter <= 5'b01111;
+				else
+				if (counter == 5'b00001)
+				begin
+					counter <= 5'd0;
+					tstate <= s_send_stop;
+				end
+				else
+					counter <= counter - 5'd1;
+				stx_o_tmp <= bit_out;
+			end
+	s_send_stop :  begin
+				if (~|counter)
+				  begin
+						casez ({lcr[`UART_LC_SB],lcr[`UART_LC_BITS]})
+  						3'b0??:	  counter <= 5'b01101;     // 1 stop bit ok igor
+  						3'b100:	  counter <= 5'b10101;     // 1.5 stop bit
+  						default:	  counter <= 5'b11101;     // 2 stop bits
+						endcase
+					end
+				else
+				if (counter == 5'b00001)
+				begin
+					counter <= 0;
+					tstate <= s_idle;
+				end
+				else
+					counter <= counter - 5'd1;
+				stx_o_tmp <= 1'b1;
+			end
+
+		default : // should never get here
+			tstate <= s_idle;
+	endcase
+  end // end if enable
+  else
+    tf_pop <= 1'b0;  // tf_pop must be 1 cycle width
+end // transmitter logic
+
+assign stx_pad_o = lcr[`UART_LC_BC] ? 1'b0 : stx_o_tmp;    // Break condition
+	
+endmodule

uart16550/uart_wb.v

@@ -0,0 +1,258 @@
+//////////////////////////////////////////////////////////////////////
+////                                                              ////
+////  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
+//
+
+`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 [2:0] 	wb_adr_i; //WISHBONE address line
+
+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;
+
+output [2:0]	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 [2:0]	wb_adr_int; // internal signal for address bus
+reg [2:0]	wb_adr_is;
+reg 								wb_we_is;
+reg 								wb_cyc_is;
+reg 								wb_stb_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: begin
+				wb_ack_o <= 0;
+				wbstate <= 3;
+				wre <= 0;
+			end
+			3: begin
+				wb_ack_o <= 0;
+				wbstate <= 0;
+				wre <= 1;
+			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;
+	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;
+	end
+
+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;
+
+
+endmodule
+
+
+
+
+
+
+
+
+
+