Subversion Repositories xulalx25soc

////////////////////////////////////////////////////////////////////////////////

//

// Filename:    uartdev.v

//

// Project:     XuLA2 board

//

// Purpose:     This is a simple wrapper around the txuart and rxuart

//              modules.  The purpose is to make both of those modules

//      configurable from a single wishbone address, and capable of receiving

//      (or transmitting) via reads (writes) from two other addresses.

//

//      It also generates interrupts: a receive interrupt strobe on the clock

//      when data is made available, and a transmit not busy level interrupt

//      which is held high as long as the transmitter is idle.  Both should be

//      able to work nicely with the programmable interrupt controllers found

//      in the ZipCPU project.

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

module  uartdev(i_clk, i_rx_uart, o_tx_uart,

                i_wb_cyc, i_wb_stb, i_wb_we, i_wb_addr, i_wb_data,

                        o_wb_ack, o_wb_stall, o_wb_data,

                o_rx_int, o_tx_int, o_debug);

        parameter       DEFAULT_SETUP = { 2'b00, 1'b0, 1'b0, 2'b00, 24'd8333 };

        input                   i_clk, i_rx_uart;

        output  wire            o_tx_uart;

        input                   i_wb_cyc, i_wb_stb, i_wb_we;

        input           [1:0]    i_wb_addr;

        input           [31:0]   i_wb_data;

        output  reg             o_wb_ack;

        output  wire            o_wb_stall;

        output  reg     [31:0]   o_wb_data;

        output  wire            o_rx_int, o_tx_int;

        output  wire    [31:0]   o_debug;

        reg     [29:0]   r_setup;

        reg             r_tx_stb, rx_rdy;

        reg     [7:0]    r_tx_data;

        initial r_setup = DEFAULT_SETUP;

        always @(posedge i_clk)

                if ((i_wb_stb)&&(i_wb_we)&&(~i_wb_addr[1]))

                        r_setup <= i_wb_data[29:0];

        initial r_tx_stb = 1'b0;

        always @(posedge i_clk)

                if ((i_wb_stb)&&(i_wb_we)&&(i_wb_addr == 2'b11))

                begin

                        // Note: there's no check for overflow here.

                        // You're on your own: verify that the device

                        // isn't busy first.

                        r_tx_data <= i_wb_data[7:0];

                        r_tx_stb <= 1'b1;

                end else

                        r_tx_stb <= 1'b0;

        wire    rx_stb, rx_break, rx_parity_err, rx_frame_err;

        wire    [7:0]    rx_data;

        rxuart  rxmod(i_clk, 1'b0, r_setup, i_rx_uart,

                        rx_stb, rx_data, rx_break,

                        rx_parity_err, rx_frame_err);

        wire    tx_break, tx_busy;

        assign  tx_break = 1'b0;

        txuart  txmod(i_clk, 1'b0, r_setup, tx_break, r_tx_stb, r_tx_data,

                        o_tx_uart, tx_busy);

        reg     [7:0]    r_data;

        always @(posedge i_clk)

                if (rx_stb)

                        r_data <= rx_data;

        initial o_wb_data = 32'h00;

        always @(posedge i_clk)

        begin

                if (rx_stb)

                        rx_rdy <= (rx_rdy | rx_stb);

                case(i_wb_addr)

                2'b00: o_wb_data <= { 2'b00, r_setup };

                2'b01: o_wb_data <= { 2'b00, r_setup };

                2'b10: begin

                        if ((i_wb_stb)&&(~i_wb_we))

                                rx_rdy <= rx_stb;

                        o_wb_data <= { 20'h00, rx_break, rx_frame_err, rx_parity_err, ~rx_rdy, r_data };

                        end

                2'b11: o_wb_data <= { 31'h00,tx_busy };

                endcase

                o_wb_ack <= (i_wb_stb); // Read or write, we ack

        end

        assign  o_wb_stall = 1'b0;

        assign  o_rx_int = rx_stb;

        assign  o_tx_int = ~tx_busy;

        assign  o_debug = { (~i_rx_uart)||(~o_tx_uart), tx_busy, i_wb_addr,

                        rx_break, rx_frame_err, rx_parity_err, rx_rdy,

                        i_wb_cyc, i_wb_stb, i_wb_we, o_wb_ack,

                        rx_stb, rx_data,

                        r_tx_stb, r_tx_data,

                        i_rx_uart, o_tx_uart };

endmodule