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 .

.at 0xc8;

    read_immed, jmp enter;

.auto_address;

enter:

    b_sel IMMEDIATE, alu_op SELB, tmp_wr_en;

    width W8, read_immed;

    // Push BP

    ra_sel SP;

    a_sel RA, b_sel IMMEDIATE, immediate 0x2, alu_op SUB, mar_write,

        mar_wr_sel Q, ra_sel BP, rd_sel_source MICROCODE_RD_SEL, rd_sel SP;

    a_sel RA, alu_op SELA, mdr_write, segment_force, segment SS;

    segment_force, segment SS, mem_write, ra_sel SP,

        jmp_loop_done enter_out_nonest;

    // Push frame temp

    a_sel RA, b_sel IMMEDIATE, alu_op ENTER_FRAME_TEMP_ADDR, mar_write,

        mar_wr_sel Q, ra_sel SP;

    a_sel RA, alu_op SELA, mdr_write, segment_force, segment SS;

    segment_force, segment SS, mem_write;

enter_loop:

    jmp_loop_done enter_out, ra_sel BP;

    // BP := BP - 2

    a_sel RA, b_sel IMMEDIATE, immediate 0x2, alu_op SUB, rd_sel BP,

        rd_sel_source MICROCODE_RD_SEL, segment_force, segment SS,

        mar_write, mar_wr_sel Q;

    // push [BP]

    segment_force, segment SS, mem_read, ra_sel SP;

    a_sel RA, b_sel IMMEDIATE, immediate 0x2, alu_op SUB, rd_sel SP,

        rd_sel_source MICROCODE_RD_SEL, segment_force, segment SS,

        mar_write, mar_wr_sel Q;

    segment_force, segment SS, mem_write;

    jmp enter_loop;

enter_out:

    // Reload frame_temp

    ra_sel SP;

    a_sel RA, b_sel IMMEDIATE, immediate 0x2, alu_op SUB, rd_sel SP,

        rd_sel_source MICROCODE_RD_SEL, segment_force, segment SS,

        mar_write, mar_wr_sel Q;

    segment_force, segment SS, mem_read, ra_sel SP;

    a_sel MDR, alu_op SELA, rd_sel BP, rd_sel_source MICROCODE_RD_SEL,

        ra_sel SP;

    // SP := SP - size

    a_sel RA, b_sel TEMP, alu_op SUB, rd_sel SP, rd_sel_source MICROCODE_RD_SEL,

        next_instruction;

enter_out_nonest:

    a_sel RA, alu_op SELA, rd_sel BP, rd_sel_source MICROCODE_RD_SEL,

        ra_sel SP;

    a_sel RA, b_sel TEMP, alu_op SUB, rd_sel SP, rd_sel_source MICROCODE_RD_SEL,

        next_instruction;