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

//

// Filename:    spio.v

//

// Project:     CMod S6 System on a Chip, ZipCPU demonstration project

//

// Purpose:     To provide a bare minimum level of access to the two on-board

//              buttons, the 4 LED's, and the external 4x4 keypad.  This

//      routine does *nothing* to debounce either buttons or keypad.  Any such

//      debouncing *must* be done in software.  As with the rest of the S6

//      project, the goal is to keep the logic small and simple, and this

//      module is no different.

//

//      With the USB cord on top, the board facing you, LED[0] is on the left.

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

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

//

// Copyright (C) 2015-2016, 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.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory, run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

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

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

//

//

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

//

//

module  spio(i_clk, i_wb_cyc, i_wb_stb, i_wb_we, i_wb_data, o_wb_data,

        o_kp_col, i_kp_row, i_btn, o_led,

        o_kp_int, o_btn_int);

        //

        input                   i_clk;

        //

        input                   i_wb_cyc, i_wb_stb, i_wb_we;

        input           [31:0]   i_wb_data;

        output  wire    [31:0]   o_wb_data;

        //

        output  reg     [3:0]    o_kp_col;

        input           [3:0]    i_kp_row;

        input           [1:0]    i_btn;

        output  reg     [3:0]    o_led;

        output  reg             o_kp_int, o_btn_int;

        initial o_kp_col = 4'h0;

        initial o_led    = 4'h0;

        always @(posedge i_clk)

                if ((i_wb_stb)&&(i_wb_we))

                begin

                        o_kp_col <= ((o_kp_col)&(~i_wb_data[11:8]))

                                        |((i_wb_data[15:12])&(i_wb_data[11:8]));

                        // o_led <= ((o_led)&(~i_wb_data[7:4]))

                                        // |((i_wb_data[3:0])&(i_wb_data[7:4]));

                        o_led[0] <= (i_wb_data[4])?i_wb_data[0]:o_led[0];

                        o_led[1] <= (i_wb_data[5])?i_wb_data[1]:o_led[1];

                        o_led[2] <= (i_wb_data[6])?i_wb_data[2]:o_led[2];

                        o_led[3] <= (i_wb_data[7])?i_wb_data[3]:o_led[3];

                end

        reg     [3:0]    x_kp_row, r_kp_row;

        reg     [1:0]    x_btn, r_btn;

        initial x_kp_row  = 4'h0;

        initial r_kp_row  = 4'b0;

        initial x_btn     = 2'b0;

        initial r_btn     = 2'b0;

        initial o_kp_int  = 1'b0;

        initial o_btn_int = 1'b0;

        always @(posedge i_clk)

        begin

                x_kp_row <= i_kp_row;

                x_btn    <= i_btn;

                r_kp_row <= x_kp_row;

                r_btn    <= x_btn;

                o_kp_int <= ~(&r_kp_row);

                o_btn_int <= |(r_btn);

        end

        assign  o_wb_data = { 16'h00, o_kp_col, r_kp_row, 2'b00, r_btn, o_led };

endmodule