Subversion Repositories s80186

// Copyright Jamie Iles, 2017
//
// This file is part of s80x86.
//
// s80x86 is free software: 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.
//
// s80x86 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with s80x86.  If not, see <http://www.gnu.org/licenses/>.

module BIOSControlRegister(input logic clk,
                           input logic reset,
                           input logic cs,
                           output logic [15:0] data_m_data_out,
                           input logic [15:0] data_m_data_in,
                           input logic data_m_wr_en,
                           input logic data_m_access,
                           output logic data_m_ack,
                           output logic bios_enabled);

always_ff @(posedge clk) begin
    data_m_data_out <= data_m_access && cs && !data_m_wr_en ?
        {15'b0, bios_enabled} : 16'b0;
    data_m_ack <= data_m_access && cs;
end

always_ff @(posedge clk or posedge reset) begin
    if (reset)
        bios_enabled <= 1'b1;
    else if (cs && data_m_access && data_m_wr_en)
        bios_enabled <= data_m_data_in[0];
end

endmodule