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_sub;

    output [15:0] out;

    input is_8_bit;

    input [15:0] a;

    input [15:0] b;

    input [15:0] flags_in;

    output [15:0] flags_out;

    begin

        flags_out = flags_in;

        if (!is_8_bit) begin

            {flags_out[CF_IDX], out} = a - b;

            flags_out[OF_IDX] = (a[15] ^ b[15]) & (out[15] ^ a[15]);

        end else begin

            out = a - b;

            flags_out[CF_IDX] = a[8] ^ b[8] ^ out[8];

            flags_out[OF_IDX] = (a[7] ^ b[7]) & (out[7] ^ a[7]);

        end

        common_flags(flags_out, is_8_bit, out, a, b);

    end

endtask

task do_sbb;

    output [15:0] out;

    input is_8_bit;

    input [15:0] a;

    input [15:0] b;

    input [15:0] flags_in;

    output [15:0] flags_out;

    begin

        flags_out = flags_in;

        if (!is_8_bit) begin

            {flags_out[CF_IDX], out} = a - b - {15'b0, flags_in[CF_IDX]};

            flags_out[OF_IDX] = (a[15] ^ b[15]) & (out[15] ^ a[15]);

        end else begin

            out = a - b - {15'b0, flags_in[CF_IDX]};

            flags_out[CF_IDX] = a[8] ^ b[8] ^ out[8];

            flags_out[OF_IDX] = (a[7] ^ b[7]) & (out[7] ^ a[7]);

        end

        common_flags(flags_out, is_8_bit, out, a, b);

    end

endtask