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 .

task do_daa;

    output [15:0] out;

    input [15:0] a;

    input [15:0] flags_in;

    output [15:0] flags_out;

    begin

        flags_out = flags_in;

        out = a;

        if (a[3:0] > 4'd9 || flags_in[AF_IDX]) begin

            reg [15:0] tmp = {8'b0, a[7:0]} + 16'd6;

            out[7:0] = tmp[7:0];

            flags_out[AF_IDX] = 1'b1;

            if (|tmp[15:8])

                flags_out[CF_IDX] = 1'b1;

        end else begin

            flags_out[AF_IDX] = 1'b0;

        end

        if (out[7:0] > 8'h9f || flags_out[CF_IDX]) begin

            out[7:0] += 8'h60;

            flags_out[CF_IDX] = 1'b1;

        end

        // Only AL is updated, but AX is an input so it's a 16-bit input, and

        // we should preserve AH so that it isn't modified.

        out = {a[15:8], out[7:0]};

    end

endtask