////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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// Filename: linetest.v
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// Filename: linetest.v
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//
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//
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// Project: wbuart32, a full featured UART with simulator
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// Project: wbuart32, a full featured UART with simulator
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//
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//
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// Purpose: To test that the txuart and rxuart modules work properly, by
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// Purpose: To test that the txuart and rxuart modules work properly, by
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// buffering one line's worth of input, and then piping that line
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// buffering one line's worth of input, and then piping that line
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// to the transmitter while (possibly) receiving a new line.
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// to the transmitter while (possibly) receiving a new line.
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//
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//
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// With some modifications (discussed below), this RTL should be able to
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// With some modifications (discussed below), this RTL should be able to
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// run as a top-level testing file, requiring only the transmit and receive
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// run as a top-level testing file, requiring only the transmit and receive
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// UART pins and the clock to work.
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// UART pins and the clock to work.
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//
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//
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// Creator: Dan Gisselquist, Ph.D.
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// Creator: Dan Gisselquist, Ph.D.
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// Gisselquist Technology, LLC
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// Gisselquist Technology, LLC
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//
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//
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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// Copyright (C) 2015-2016, Gisselquist Technology, LLC
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// Copyright (C) 2015-2016, Gisselquist Technology, LLC
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//
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//
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// This program is free software (firmware): you can redistribute it and/or
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// This program is free software (firmware): you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as published
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// modify it under the terms of the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or (at
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// by the Free Software Foundation, either version 3 of the License, or (at
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// your option) any later version.
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// your option) any later version.
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//
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// for more details.
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//
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//
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// You should have received a copy of the GNU General Public License along
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// You should have received a copy of the GNU General Public License along
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// with this program. (It's in the $(ROOT)/doc directory, run make with no
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// with this program. (It's in the $(ROOT)/doc directory, run make with no
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// target there if the PDF file isn't present.) If not, see
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// target there if the PDF file isn't present.) If not, see
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// <http://www.gnu.org/licenses/> for a copy.
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// <http://www.gnu.org/licenses/> for a copy.
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//
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//
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// License: GPL, v3, as defined and found on www.gnu.org,
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// License: GPL, v3, as defined and found on www.gnu.org,
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// http://www.gnu.org/licenses/gpl.html
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// http://www.gnu.org/licenses/gpl.html
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//
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//
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//
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//
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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//
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//
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//
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//
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// One issue with the design is how to set the values of the setup register.
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// One issue with the design is how to set the values of the setup register.
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// (*This is a comment, not a verilator attribute ... ) Verilator needs to
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// (*This is a comment, not a verilator attribute ... ) Verilator needs to
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// know/set those values in order to work. However, this design can also be
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// know/set those values in order to work. However, this design can also be
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// used as a stand-alone top level configuration file. In this latter case,
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// used as a stand-alone top level configuration file. In this latter case,
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// the setup register needs to be set internal to the file. Here, we use
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// the setup register needs to be set internal to the file. Here, we use
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// OPT_STANDALONE to distinguish between the two. If set, the file runs under
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// OPT_STANDALONE to distinguish between the two. If set, the file runs under
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// (* Another comment still ...) Verilator and we need to get i_setup from the
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// (* Another comment still ...) Verilator and we need to get i_setup from the
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// external environment. If not, it must be set internally.
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// external environment. If not, it must be set internally.
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//
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//
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`ifndef VERILATOR
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`ifndef VERILATOR
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`define OPT_STANDALONE
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`define OPT_STANDALONE
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`endif
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`endif
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//
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//
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//
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// Two versions of the UART can be found in the rtl directory: a full featured
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// UART, and a LITE UART that only handles 8N1 -- no break sending, break
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// detection, parity error detection, etc. If we set USE_LITE_UART here, those
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// simplified UART modules will be used.
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//
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// `define USE_LITE_UART
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//
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//
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module linetest(i_clk,
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module linetest(i_clk,
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`ifndef OPT_STANDALONE
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`ifndef OPT_STANDALONE
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i_setup,
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i_setup,
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`endif
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`endif
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i_uart_rx, o_uart_tx);
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i_uart_rx, o_uart_tx);
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input i_clk;
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input i_clk;
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`ifndef OPT_STANDALONE
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`ifndef OPT_STANDALONE
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input [30:0] i_setup;
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input [30:0] i_setup;
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`endif
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`endif
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input i_uart_rx;
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input i_uart_rx;
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output wire o_uart_tx;
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output wire o_uart_tx;
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// If i_setup isnt set up as an input parameter, it needs to be set.
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// If i_setup isnt set up as an input parameter, it needs to be set.
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// We do so here, to a setting appropriate to create a 115200 Baud
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// We do so here, to a setting appropriate to create a 115200 Baud
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// comms system from a 100MHz clock. This also sets us to an 8-bit
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// comms system from a 100MHz clock. This also sets us to an 8-bit
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// data word, 1-stop bit, and no parity.
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// data word, 1-stop bit, and no parity.
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`ifdef OPT_STANDALONE
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`ifdef OPT_STANDALONE
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wire [30:0] i_setup;
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wire [30:0] i_setup;
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assign i_setup = 31'd868; // 115200 Baud, if clk @ 100MHz
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assign i_setup = 31'd868; // 115200 Baud, if clk @ 100MHz
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`endif
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`endif
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reg [7:0] buffer [0:255];
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reg [7:0] buffer [0:255];
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reg [7:0] head, tail;
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reg [7:0] head, tail;
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// Create a reset line that will always be true on a power on reset
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// Create a reset line that will always be true on a power on reset
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reg pwr_reset;
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reg pwr_reset;
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initial pwr_reset = 1'b1;
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initial pwr_reset = 1'b1;
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always @(posedge i_clk)
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always @(posedge i_clk)
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pwr_reset = 1'b0;
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pwr_reset = 1'b0;
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// The UART Receiver
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// The UART Receiver
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//
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//
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// This is where everything begins, by reading data from the UART.
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// This is where everything begins, by reading data from the UART.
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//
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//
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// Data (rx_data) is present when rx_stb is true. Any parity or
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// Data (rx_data) is present when rx_stb is true. Any parity or
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// frame errors will also be valid at that time. Finally, we'll ignore
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// frame errors will also be valid at that time. Finally, we'll ignore
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// errors, and even the clocked uart input distributed from here.
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// errors, and even the clocked uart input distributed from here.
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wire rx_stb, rx_break, rx_perr, rx_ferr, rx_ignored;
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wire rx_stb, rx_break, rx_perr, rx_ferr, rx_ignored;
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wire [7:0] rx_data;
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wire [7:0] rx_data;
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`ifdef USE_LITE_UART
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rxuartlite #(24'd868)
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receiver(i_clk, i_uart_rx, rx_stb, rx_data);
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`else
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rxuart receiver(i_clk, pwr_reset, i_setup, i_uart_rx, rx_stb, rx_data,
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rxuart receiver(i_clk, pwr_reset, i_setup, i_uart_rx, rx_stb, rx_data,
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rx_break, rx_perr, rx_ferr, rx_ignored);
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rx_break, rx_perr, rx_ferr, rx_ignored);
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`endif
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// The next step in this process is to dump everything we read into a
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// The next step in this process is to dump everything we read into a
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// FIFO. First step: writing into the FIFO. Always write into FIFO
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// FIFO. First step: writing into the FIFO. Always write into FIFO
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// memory. (The next step will step the memory address if rx_stb was
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// memory. (The next step will step the memory address if rx_stb was
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// true ...)
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// true ...)
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wire [7:0] nxt_head;
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wire [7:0] nxt_head;
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assign nxt_head = head + 8'h01;
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assign nxt_head = head + 8'h01;
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always @(posedge i_clk)
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always @(posedge i_clk)
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buffer[head] <= rx_data;
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buffer[head] <= rx_data;
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// Select where in our FIFO memory to write. On reset, we clear the
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// Select where in our FIFO memory to write. On reset, we clear the
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// memory. In all other cases/respects, we step the memory forward.
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// memory. In all other cases/respects, we step the memory forward.
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//
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//
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// However ... we won't step it forward IF ...
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// However ... we won't step it forward IF ...
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// rx_break - we are in a BREAK condition on the line
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// rx_break - we are in a BREAK condition on the line
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// (i.e. ... it's disconnected)
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// (i.e. ... it's disconnected)
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// rx_perr - We've seen a parity error
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// rx_perr - We've seen a parity error
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// rx_ferr - Same thing for a frame error
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// rx_ferr - Same thing for a frame error
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// nxt_head != tail - If the FIFO is already full, we'll just drop
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// nxt_head != tail - If the FIFO is already full, we'll just drop
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// this new value, rather than dumping random garbage
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// this new value, rather than dumping random garbage
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// from the FIFO until we go round again ... i.e., we
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// from the FIFO until we go round again ... i.e., we
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// don't write on potential overflow.
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// don't write on potential overflow.
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//
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//
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// Adjusting this address will make certain that the next write to the
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// Adjusting this address will make certain that the next write to the
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// FIFO goes to the next address--since we've already written the FIFO
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// FIFO goes to the next address--since we've already written the FIFO
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// memory at this address.
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// memory at this address.
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initial head= 8'h00;
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initial head= 8'h00;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (pwr_reset)
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if (pwr_reset)
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head <= 8'h00;
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head <= 8'h00;
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else if ((rx_stb)&&(!rx_break)&&(!rx_perr)&&(!rx_ferr)&&(nxt_head != tail))
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else if ((rx_stb)&&(!rx_break)&&(!rx_perr)&&(!rx_ferr)&&(nxt_head != tail))
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head <= nxt_head;
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head <= nxt_head;
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wire [7:0] nused;
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wire [7:0] nused;
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reg [7:0] lineend;
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reg [7:0] lineend;
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reg run_tx;
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reg run_tx;
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// How much of the FIFO is in use? head - tail. What if they wrap
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// How much of the FIFO is in use? head - tail. What if they wrap
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// around? Still: head-tail, but this time truncated to the number of
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// around? Still: head-tail, but this time truncated to the number of
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// bits of interest. It can never be negative ... so ... we're good,
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// bits of interest. It can never be negative ... so ... we're good,
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// this just measures that number.
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// this just measures that number.
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assign nused = head-tail;
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assign nused = head-tail;
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// Here's the guts of the algorithm--setting run_tx. Once set, the
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// Here's the guts of the algorithm--setting run_tx. Once set, the
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// buffer will flush. Here, we set it on one of two conditions: 1)
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// buffer will flush. Here, we set it on one of two conditions: 1)
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// a newline is received, or 2) the line is now longer than 80
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// a newline is received, or 2) the line is now longer than 80
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// characters.
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// characters.
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//
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//
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// Once the line has ben transmitted (separate from emptying the buffer)
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// Once the line has ben transmitted (separate from emptying the buffer)
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// we stop transmitting.
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// we stop transmitting.
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initial run_tx = 0;
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initial run_tx = 0;
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initial lineend = 0;
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initial lineend = 0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if (pwr_reset)
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if (pwr_reset)
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begin
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begin
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run_tx <= 1'b0;
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run_tx <= 1'b0;
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lineend <= 8'h00;
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lineend <= 8'h00;
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end else if(((rx_data == 8'h0a)||(rx_data == 8'hd))&&(rx_stb))
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end else if(((rx_data == 8'h0a)||(rx_data == 8'hd))&&(rx_stb))
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begin
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begin
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// Start transmitting once we get to either a newline
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// Start transmitting once we get to either a newline
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// or a carriage return character
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// or a carriage return character
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lineend <= head+8'h1;
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lineend <= head+8'h1;
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run_tx <= 1'b1;
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run_tx <= 1'b1;
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end else if ((!run_tx)&&(nused>8'd80))
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end else if ((!run_tx)&&(nused>8'd80))
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begin
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begin
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// Start transmitting once we get to 80 chars
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// Start transmitting once we get to 80 chars
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lineend <= head;
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lineend <= head;
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run_tx <= 1'b1;
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run_tx <= 1'b1;
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end else if (tail == lineend)
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end else if (tail == lineend)
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// Line buffer has been emptied
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// Line buffer has been emptied
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run_tx <= 1'b0;
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run_tx <= 1'b0;
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// Now ... let's deal with the transmitter
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// Now ... let's deal with the transmitter
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wire tx_break, tx_busy;
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wire tx_break, tx_busy;
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assign tx_break = 1'b0;
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assign tx_break = 1'b0;
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reg [7:0] tx_data;
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reg [7:0] tx_data;
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reg tx_stb;
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reg tx_stb;
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// When do we wish to transmit?
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// When do we wish to transmit?
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//
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//
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// Any time run_tx is true--but we'll give it an extra clock.
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// Any time run_tx is true--but we'll give it an extra clock.
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initial tx_stb = 1'b0;
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initial tx_stb = 1'b0;
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always @(posedge i_clk)
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always @(posedge i_clk)
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tx_stb <= run_tx;
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tx_stb <= run_tx;
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// We'll transmit the data from our FIFO from ... wherever our tail
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// We'll transmit the data from our FIFO from ... wherever our tail
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// is pointed.
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// is pointed.
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always @(posedge i_clk)
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always @(posedge i_clk)
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tx_data <= buffer[tail];
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tx_data <= buffer[tail];
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// We increment the pointer to where we read from any time 1) we are
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// We increment the pointer to where we read from any time 1) we are
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// requesting to transmit a character, and 2) the transmitter was not
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// requesting to transmit a character, and 2) the transmitter was not
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// busy and thus accepted our request. At that time, increment the
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// busy and thus accepted our request. At that time, increment the
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// pointer, and we'll be ready for another round.
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// pointer, and we'll be ready for another round.
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initial tail = 8'h00;
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initial tail = 8'h00;
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always @(posedge i_clk)
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always @(posedge i_clk)
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if(pwr_reset)
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if(pwr_reset)
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tail <= 8'h00;
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tail <= 8'h00;
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else if ((tx_stb)&&(!tx_busy))
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else if ((tx_stb)&&(!tx_busy))
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tail <= tail + 8'h01;
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tail <= tail + 8'h01;
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// Bypass any hardwaare flow control
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// Bypass any hardwaare flow control
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wire rts;
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wire cts_n;
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assign rts = 1'b1;
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assign cts_n = 1'b0;
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`ifdef USE_LITE_UART
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txuartlite #(24'd868)
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transmitter(i_clk, tx_stb, tx_data, o_uart_tx, tx_busy);
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`else
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txuart transmitter(i_clk, pwr_reset, i_setup, tx_break,
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txuart transmitter(i_clk, pwr_reset, i_setup, tx_break,
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tx_stb, tx_data, rts, o_uart_tx, tx_busy);
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tx_stb, tx_data, cts_n, o_uart_tx, tx_busy);
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`endif
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endmodule
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endmodule
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