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//////////////////////////////////////////////////////////////////////
//// ////
//// 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: uart_transmitter.v,v $
// Revision 1.19 2002/07/29 21:16:18 gorban
// The uart_defines.v file is included again in sources.
//
// 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
//
//
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "uart_defines.v"
module uart_transmitter (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
reg [`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;
always @(posedge clk)
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
parameter s_idle = 3'd0;
parameter s_send_start = 3'd1;
parameter s_send_byte = 3'd2;
parameter s_send_parity = 3'd3;
parameter s_send_stop = 3'd4;
parameter s_pop_byte = 3'd5;
always @(posedge clk or posedge wb_rst_i)
begin
if (wb_rst_i)
begin
tstate <= #1 s_idle;
stx_o_tmp <= #1 1'b1;
counter <= #1 5'b0;
shift_out <= #1 7'b0;
bit_out <= #1 1'b0;
parity_xor <= #1 1'b0;
tf_pop <= #1 1'b0;
bit_counter <= #1 3'b0;
end
else
if (enable)
begin
case (tstate)
s_idle : if (~|tf_count) // if tf_count==0
begin
tstate <= #1 s_idle;
stx_o_tmp <= #1 1'b1;
end
else
begin
tf_pop <= #1 1'b0;
stx_o_tmp <= #1 1'b1;
tstate <= #1 s_pop_byte;
end
s_pop_byte : begin
tf_pop <= #1 1'b1;
case (lcr[/*`UART_LC_BITS*/1:0]) // number of bits in a word
2'b00 : begin
bit_counter <= #1 3'b100;
parity_xor <= #1 ^tf_data_out[4:0];
end
2'b01 : begin
bit_counter <= #1 3'b101;
parity_xor <= #1 ^tf_data_out[5:0];
end
2'b10 : begin
bit_counter <= #1 3'b110;
parity_xor <= #1 ^tf_data_out[6:0];
end
2'b11 : begin
bit_counter <= #1 3'b111;
parity_xor <= #1 ^tf_data_out[7:0];
end
endcase
{shift_out[6:0], bit_out} <= #1 tf_data_out;
tstate <= #1 s_send_start;
end
s_send_start : begin
tf_pop <= #1 1'b0;
if (~|counter)
counter <= #1 5'b01111;
else
if (counter == 5'b00001)
begin
counter <= #1 0;
tstate <= #1 s_send_byte;
end
else
counter <= #1 counter - 1'b1;
stx_o_tmp <= #1 1'b0;
end
s_send_byte : begin
if (~|counter)
counter <= #1 5'b01111;
else
if (counter == 5'b00001)
begin
if (bit_counter > 3'b0)
begin
bit_counter <= #1 bit_counter - 1'b1;
{shift_out[5:0],bit_out } <= #1 {shift_out[6:1], shift_out[0]};
tstate <= #1 s_send_byte;
end
else // end of byte
if (~lcr[`UART_LC_PE])
begin
tstate <= #1 s_send_stop;
end
else
begin
case ({lcr[`UART_LC_EP],lcr[`UART_LC_SP]})
2'b00: bit_out <= #1 ~parity_xor;
2'b01: bit_out <= #1 1'b1;
2'b10: bit_out <= #1 parity_xor;
2'b11: bit_out <= #1 1'b0;
endcase
tstate <= #1 s_send_parity;
end
counter <= #1 0;
end
else
counter <= #1 counter - 1'b1;
stx_o_tmp <= #1 bit_out; // set output pin
end
s_send_parity : begin
if (~|counter)
counter <= #1 5'b01111;
else
if (counter == 5'b00001)
begin
counter <= #1 4'b0;
tstate <= #1 s_send_stop;
end
else
counter <= #1 counter - 1'b1;
stx_o_tmp <= #1 bit_out;
end
s_send_stop : begin
if (~|counter)
begin
casex ({lcr[`UART_LC_SB],lcr[`UART_LC_BITS]})
3'b0xx: counter <= #1 5'b01101; // 1 stop bit ok igor
3'b100: counter <= #1 5'b10101; // 1.5 stop bit
default: counter <= #1 5'b11101; // 2 stop bits
endcase
end
else
if (counter == 5'b00001)
begin
counter <= #1 0;
tstate <= #1 s_idle;
end
else
counter <= #1 counter - 1'b1;
stx_o_tmp <= #1 1'b1;
end
default : // should never get here
tstate <= #1 s_idle;
endcase
end // end if enable
else
tf_pop <= #1 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
|
