function machine_6502(start_address) { function assemble(machine, assembly) { var binary_code = [] var byte_addresses = [] var byte_address = 0 var line_byte_addresses = [] var instruction_lengths = [] var labels = {} var labels_pass_2 = [] let assembly_lines = assembly.split("\n") for (var k = 0; k < assembly_lines.length; k++){ var byte_address_line = byte_address; var assembly_line_trim = assembly_lines[k].trim().split(";")[0] if (assembly_line_trim == "") { instruction_lengths.push(0); } else { var assembly_line_split = assembly_line_trim.split(" "); var a = assembly_line_split.filter(function (e) {return e != '';}); if (a.length > 0) { if (a[0].slice(-1) == ":") { var label = a[0].slice(0, -1); if (label.length > 0 && /^[a-z][a-z0-9]+$/.test(label)) { labels[label] = byte_address; a.shift(); } else { return {"error": "Incorrect label format for " + label}; } } } if (a.length > 0) { if (a.length > 2) { a = [a[0], a.slice(1).join("")]; } if (a.length == 2) { var hex = a[1].match(/\$[0-9a-fA-F]+/g); console.log(a[1]); if (hex != null) { for(var i=0; i 1) { var arg_value = a[1].match(/[0-9]+/)[0]; if (parseInt(arg_value) > 255) { possible_args = possible_args.filter(function(value) { return value[1] != "zpg" && value[1] != "zpg,X"; }) } } if (possible_args.length == 0){ return {"error": "Invalid opcode & addressing mode combination " + a, "assembly_output": ""}; } var opcode = possible_args[0][0]; var args = possible_args[0][1]; var code_length = machine.instructions.lengths[args]; binary_code.push(parseInt(opcode)); byte_addresses.push(byte_address); byte_address += 1; if (labels_found != null) { if (a.length > 1 && labels_found.length > 0) { for(var i=0; i 0) { var fer = execution_record[execution_record.length - 1]; var f = fer.flags; var r = fer.registers; machine.state.flags = {"c": f.c, "n": f.n, "z": f.z, "d": f.d, "v": f.v, "i":f.i} machine.state.registers = {"a": r.a, "x": r.x, "y":r.y, "p":r.p, "pc":r.pc, "sp":r.sp} for (var i = 0; i < fer.memory_changes.length; i++) { var mc = fer.memory_changes[i]; memory[mc.address] = mc.old; } machine.state.cycles = machine.state.cycles - fer.cycles; execution_record.pop(); } return machine; } function execute_instructions(machine, no_instructions, no_cycles) { var instructions = machine.instructions.opcodes; var flag = machine.state.flags; var reg = machine.state.registers; var memory = machine.state.memory; var memory_type = machine.state.memory_type; var cycles = machine.state.cycles; var execution_records = machine.state.execution_records; const max_execution_records = 1000; let branch_options = {}; branch_options["CC"] = ["C", 0]; branch_options["CS"] = ["C", 1]; branch_options["EQ"] = ["Z", 1]; branch_options["NE"] = ["Z", 0]; branch_options["PL"] = ["N", 0]; branch_options["NI"] = ["N", 1]; branch_options["VC"] = ["V", 0]; branch_options["VS"] = ["V", 1]; function set_memory(address, value) { memory_changes.push({"address": address, "old": memory[address], "new": value}); memory[address] = value; } function push(byte) { set_memory(reg.sp + 0x100, byte); reg.sp = (reg.sp - 1) & 0xff; } function pop() { reg.sp = (reg.sp + 1) & 0xff; return memory[reg.sp + 0x100]; } function update_flags() { flag.n = (reg.p & 0x80) / 0x80; flag.v = (reg.p & 0x40) / 0x40; flag.d = (reg.p & 0x08) / 0x08; flag.i = (reg.p & 0x04) / 0x04; flag.z = (reg.p & 0x02) / 0x02; flag.c = (reg.p & 0x01) / 0x01; } function test_nz(v) { if (v == 0) { flag.z = 1; } else { flag.z = 0; } if ((v & 0x80) == 0) { flag.n = 0; } else { flag.n = 1; } } function test_nzc(v, a, c) { test_nz(v); if (a < c) { flag.c = 0; } else { flag.c = 1; } } var i_no = 1; var c_no = 1; while (true) { var memory_changes = []; var reg_old = JSON.parse(JSON.stringify(reg)); var flag_old = JSON.parse(JSON.stringify(flag)); if (memory[reg.pc] == -1) { return machine; } if (no_instructions != 0 && i_no > no_instructions) { return machine; } if (no_cycles != 0 && c_no > no_cycles) { return machine; } var op = instructions[memory[reg.pc]]; var opc = op["code"]; var opm = op["mode"]; var b2 = memory[(reg.pc + 1) & 0xffff]; var b3 = memory[(reg.pc + 2) & 0xffff]; var abs = (b3 * 256 + b2) & 0xffff; var cross_page = 0; var pc_inc = machine.instructions.lengths[opm]; switch (opm) { case "(zpg,X)": var address = memory[(b2 + reg.x) & 0xff] * 256 + memory[(b2 + reg.x + 1) & 0xff]; var operand = memory[address]; break; case "zpg": address = b2; operand = memory[b2]; break; case "#": operand = b2; break; case "abs": address = abs; operand = memory[abs]; break; case "(zpg),Y": address = (memory[b2] * 256 + memory[(b2 + 1) & 0xff] + reg.y + flag.c) & 0xffff; if (((memory[b2] * 256 + memory[(b2 + 1) & 0xff]) & 0xFF00) != (address & 0xFF00)) { cross_page = 1; } operand = memory[address]; break; case "zpg,X": address = (b2 + reg.x) & 0xff; operand = memory[address]; break; case "zpg,Y": address = (b2 + reg.y) & 0xff; operand = memory[address]; break; case "abs,Y": address = (b2 * 256 + b3 + reg.y + flag.c) & 0xffff; if ((abs & 0xFF00) != (address & 0xFF00)) { cross_page = 1; } operand = memory[address]; break; case "abs,X": address = (b2 * 256 + b3 + reg.x + flag.c) & 0xffff; if ((abs & 0xFF00) != (address & 0xFF00)) { cross_page = 1; } operand = memory[address]; break; case "A": operand = reg.a; break; case "(abs)": address = memory[abs] + 256 * memory[(abs + 1) & 0xffff]; break; } var op_letter_23 = opc.substring(0, 2); if (opc[0] == "B" && (opc != "BRK" && opc != "BIT")) { var branch_details = branch_options[opc.substring(1, 3)]; if (flag[branch_details[0].toLowerCase()] == branch_details[1]) { var branch_vector = b2 < 128 ? b2 : b2 + 256 * 255; if ((reg.pc & 0xFF00) != ((reg.pc + branch_vector) & 0xFF00)) { cross_page = 1; } reg.pc = (reg.pc + branch_vector) & 0xffff; } } else if (op_letter_23 == "ST") { set_memory(address, reg[opc.substring(2).toLowerCase()]); } else if (op_letter_23 == "LD") { reg[opc.substring(2).toLowerCase()] = operand; test_nz(operand); } else if (op_letter_23 == "SE") { flag[opc.substring(2).toLowerCase()] = 1; } else if (op_letter_23 == "CL") { flag[opc.substring(2).toLowerCase()] = 0; } else if (op_letter_23 == "PH") { if (opc == "PHA") { push(reg.a); } else { push(reg.p); } } else if (op_letter_23 == "PL") { if (opc == "PLA") { reg.a = pop(); } else { reg.p = pop(); update_flags(); } } else if (opc[0] == "T") { reg[opc[2].toLowerCase()] = reg[opc[1].toLowerCase()]; } else { switch (opc) { case "ORA": reg.a = reg.a | operand; test_nz(reg.a); break; case "AND": reg.a = reg.a & operand; test_nz(reg.a); break; case "EOR": reg.a = reg.a ^ operand; test_nz(reg.a); break; case "ADC": if (flags.d != 1) { var tmpa = reg.a + operand + flag.c; reg.a = tmpa & 0xff; flag.c = (tmpa & 0x100) / 0x100; test_nz(reg.a); } else { var tmpa = (reg.a & 0x0F) + (operand & 0x0F) + flag.c; if (tmpa > 9) { var bcd_c = 1; tmpa = tmpa - 10; } else { var bcd_c = 0; } var tmpb = (reg.a & 0xF0) / 16 + (operand & 0xF0) / 16 + bcd_c; if (tmpb > 9) { flag.c = 1; tmpb = tmpb - 10; } else { flag.c = 0; } reg.a = tmpa + tmpb * 16; test_nz(reg.a); } break; case "CMP": test_nzc(reg.a - operand, reg.a, operand); break; case "CPX": test_nzc(reg.x - operand, reg.x, operand); break; case "CPY": test_nzc(reg.y - operand, reg.y, operand); break; case "SBC": if (flags.d != 1) { tmpa = reg.a - operand - flag.c; reg.a = tmpa & 0xff; if (tmpa < 0) { flag.c = 1; } else { flag.c = 0; } test_nz(reg.a); } else { var tmpa = (reg.a & 0x0F) - (operand & 0x0F) - flag.c; if (tmpa < 0) { var bcd_c = 1; tmpa = tmpa + 10; } else { var bcd_c = 0; } var tmpb = ((reg.a & 0xF0) / 16) - ((operand & 0xF0) / 16) - bcd_c; if (tmpb < 0) { flag.c = 1; tmpb = tmpb + 10; } else { flag.c = 0; } reg.a = tmpa + tmpb * 16; test_nz(reg.a); } break; case "ASL": if (opm != "A") { var tmpa = memory[address] * 2; flag.c = tmpa & 0x100; set_memory(address, tmpa & 0xff); } else { reg.a = reg.a * 2; flag.c = reg.a & 0x100; reg.a = reg.a & 0xff; } break; case "ROL": if (opm != "A") { var tmpa = memory[address] * 2 + flag.c; flag.c = tmpa & 0x100; set_memory(address, tmpa & 0xff); } else { reg.a = reg.a * 2 + flag.c; flag.c = reg.a & 0x100; reg.a = reg.a & 0xff; } break; case "LSR": if (opm != "A") { flag.c = memory[address] & 0x1; set_memory(address, Math.floor(memory[address] / 2)); } else { flag.c = reg.a & 0x1; reg.a = Math.floor(reg.a / 2); } break; case "ROR": if (opm != "A") { var tmp_fc = flag.c; flag.c = memory[address] & 0x1; set_memory(address, Math.floor(memory[address] / 2) + 128 * tmp_fc); } else { var tmp_fc = flag.c; flag.c = reg.a & 0x1; reg.a = Math.floor(reg.a / 2) + 128 * tmp_fc; } break; case "BRK": push((reg.pc + 2) & 0xff); push(((reg.pc + 2) & 0xff00) / 256); push(reg.p); flag.i = 1; reg.pc = memory[0xffff] * 0x100 + memory[0xffff - 1]; pc_inc = 0; break; case "BIT": if (reg.a & (operand == 0)) { flag.z = 1; } else { flag.z = 0; } flag.n = (operand & 0x80) / 0x80; flag.v = (operand & 0x40) / 0x40; update_flags(); break; case "JSR": push(((reg.pc + 3) & 0xff00) / 256); push((reg.pc + 3) & 0xff); reg.pc = address; pc_inc = 0; break; case "RTI": reg.p = pop(); update_flags(); reg.pc = 0x100 * pop() + pop(); pc_inc = 0; break; case "RTS": var low_pop_address = pop(); reg.pc = 0x100 * pop() + low_pop_address; pc_inc = 0; break; case "DEC": set_memory(address, (memory[address] - 1) & 0xff); test_nz(memory[address]); break; case "INC": set_memory(address, (memory[address] + 1) & 0xff); test_nz(memory[address]); break; case "DEX": reg.x = (reg.x - 1) & 0xff; test_nz(reg.x); break; case "DEY": reg.y = (reg.y - 1) & 0xff; test_nz(reg.y); break; case "INX": reg.x = (reg.x + 1) & 0xff; test_nz(reg.x); break; case "INY": reg.y = (reg.y + 1) & 0xff; test_nz(reg.y); break; case "JMP": reg.pc = address; pc_inc = 0; break; case "NOP": break; } } reg.pc = (reg.pc + pc_inc) & 0xffff; var cycles_new = calculate_cycles(opc, opm, cross_page); machine.state.cycles += cycles_new; machine.state.execution_record.push(JSON.parse(JSON.stringify({"registers": reg_old, "flags": flag_old, "memory_changes": memory_changes, "cycles": cycles_new}))) if (execution_record.length > max_execution_records) { execution_record.shift(); } i_no += 1; c_no += cycles_new; } return machine; } var instructions = {}; instructions.opcodes = generate_instructions_opcodes(); instructions.index = generate_instructions_index(instructions.opcodes); instructions.lengths = generate_instructions_lengths(); instructions.instruction_descriptions = generate_instruction_descriptions(); instructions.mode_descriptions = generate_mode_descriptions(); instructions.argument_options = generate_argument_options(); var registers = generate_registers(["a", "x", "y", "sp", "pc", "p"]); var flags = generate_registers(["n", "v", "d" ,"i", "z", "c"]) registers.pc = parseInt(start_address); // Bit 5 of registers / P register is always set to 1 registers.p = 0x10; var memory = init_memory(); // memory type : 0 = RAM, 1 = ROM var memory_type = init_memory(); var cycles = 0; var execution_record = []; return {"instructions":instructions, "state": {"registers":registers, "flags":flags, "memory":memory, "memory_type": memory_type, "cycles":cycles, "execution_record": execution_record}, "execute":execute_instructions, "assemble":assemble, "backstep":backstep, "save_memory":save_memory, "reset":reset}; }