272 lines
7.2 KiB
JavaScript
272 lines
7.2 KiB
JavaScript
const { INITIAL_IP_ADDRESS, CYCLE_LIMIT } = require('./machine.config');
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const { num2hex, num2bin_4bit } = require('./logging.js');
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const display = require('./display.js');
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// TODO:
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// implement setting and clearing of:
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// - [ ] overflow flag
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// - [ ] zero flag
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// - [ ] negative flag
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// STATE
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const CPU = {
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running: false,
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IP: INITIAL_IP_ADDRESS,
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FLAGS: 0, // A bit field! 0000 = NZOC
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Acc: 0,
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memory: null,
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currentInstruction: {
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opcode: null,
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operand: null,
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mnemonic: null,
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},
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/** @param {Uint8Array} data */
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loadMemory: (data) => {
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if (data.length > 256) { throw new Error("Out of memory error (program too long)"); }
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CPU.memory = data;
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},
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setFlagNegative: () => { CPU.FLAGS |= 8 },
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setFlagZero: () => { CPU.FLAGS |= 4 },
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setFlagOverflow: () => { CPU.FLAGS |= 2 },
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setFlagCarry: () => { CPU.FLAGS |= 1 },
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unsetFlagNegative: () => { CPU.FLAGS &= ~8 },
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unsetFlagZero: () => { CPU.FLAGS &= ~4 },
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unsetFlagOverflow: () => { CPU.FLAGS &= ~2 },
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unsetFlagCarry: () => { CPU.FLAGS &= ~1 },
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}
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// FUNCTIONS THAT MODIFY STATE
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const Instructions = {
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end: () => {
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CPU.currentInstruction.mnemonic = 'END';
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CPU.running = false;
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},
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store_lit: (lit) => {
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CPU.currentInstruction.mnemonic = 'STO lit';
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CPU.memory[lit] = CPU.Acc;
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CPU.IP = CPU.IP += 2;
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},
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store_addr: (addr) => {
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CPU.currentInstruction.mnemonic = 'STO addr';
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CPU.memory[CPU.memory[addr]] = CPU.Acc;
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CPU.IP = CPU.IP += 2;
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},
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load_lit: (lit) => {
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CPU.currentInstruction.mnemonic = 'LDA lit';
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CPU.Acc = lit;
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CPU.IP = CPU.IP += 2;
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},
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load_addr: (addr) => {
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CPU.currentInstruction.mnemonic = `LDA addr; @ addr: ${num2hex(CPU.memory[addr])}`;
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CPU.Acc = CPU.memory[addr];
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CPU.IP = CPU.IP += 2;
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},
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add_lit: (lit) => {
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CPU.currentInstruction.mnemonic = 'ADD lit';
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let sum = CPU.Acc + lit;
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// TODO: implement NZO flags
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if (sum > 255) {
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CPU.setFlagCarry();
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CPU.Acc = (sum % 255) - 1;
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} else {
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CPU.unsetFlagCarry();
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CPU.Acc = sum;
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}
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CPU.IP = CPU.IP += 2;
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},
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add_addr: (addr) => {
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CPU.currentInstruction.mnemonic = 'ADD addr';
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let sum = CPU.Acc + CPU.memory[addr];
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// TODO: implement NZO flags
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if (sum > 255) {
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CPU.setFlagCarry();
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CPU.Acc = (sum % 255) - 1;
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} else {
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CPU.unsetFlagCarry();
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CPU.Acc = sum;
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}
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CPU.IP = CPU.IP += 2;
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},
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sub_lit: (lit) => {
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CPU.currentInstruction.mnemonic = 'SUB lit';
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let sum = CPU.Acc - lit;
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// TODO: implement NZO flags
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if (sum < 0) {
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CPU.setFlagCarry();
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CPU.Acc = 255 + sum + 1;
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} else {
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CPU.unsetFlagCarry();
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CPU.Acc = sum;
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}
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CPU.IP = CPU.IP += 2;
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},
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sub_addr: (addr) => {
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CPU.currentInstruction.mnemonic = 'SUB addr';
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let sum = CPU.Acc - CPU.memory[addr];
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// TODO: implement NZO flags
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if (sum < 0) {
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CPU.setFlagCarry();
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CPU.Acc = 255 + sum + 1;
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} else {
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CPU.unsetFlagCarry();
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CPU.Acc = sum;
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}
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CPU.IP = CPU.IP += 2;
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},
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hop_lit: (lit) => {
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CPU.currentInstruction.mnemonic = `HOP lit; IP+2: ${CPU.memory[CPU.IP+2]}, IP+3: ${CPU.memory[CPU.IP+3]}`;
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if (CPU.Acc === lit) {
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CPU.IP += 4;
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} else {
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CPU.IP += 2;
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}
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},
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hop_addr: (addr) => {
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CPU.currentInstruction.mnemonic = 'HOP addr';
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if (CPU.Acc === CPU.memory[addr]) {
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CPU.IP += 4;
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} else {
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CPU.IP += 2;
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}
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},
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jump_lit: (lit) => {
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CPU.currentInstruction.mnemonic = 'JMP lit';
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CPU.IP = lit;
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},
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jump_addr: (addr) => {
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CPU.currentInstruction.mnemonic = 'JMP addr';
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CPU.IP = CPU.memory[addr];
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},
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flag_toggle: (flagNum) => {
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CPU.currentInstruction.mnemonic = 'FTG';
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let mask = null;
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if (flagNum === 0) { mask = 1; }
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if (flagNum === 1) { mask = 2; }
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if (flagNum === 2) { mask = 4; }
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if (flagNum === 3) { mask = 8; }
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if (mask === null) { throw new Error('Invalid flag number'); }
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console.log('flag mask:', mask);
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CPU.FLAGS = CPU.FLAGS ^= mask;
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CPU.IP += 2;
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},
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flag_hop: (flagNum) => {
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CPU.currentInstruction.mnemonic = `FHP; IP+2: ${CPU.memory[CPU.IP+2]}, IP+3: ${CPU.memory[CPU.IP+3]}`;
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console.log('flag number:', flagNum);
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let mask = null;
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if (flagNum === 0) { mask = 1; }
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if (flagNum === 1) { mask = 2; }
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if (flagNum === 2) { mask = 4; }
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if (flagNum === 3) { mask = 8; }
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if (mask === null) { throw new Error('Invalid flag number'); }
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console.log('flag mask:', mask);
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if (CPU.FLAGS & mask) {
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CPU.IP += 4;
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} else {
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CPU.IP += 2;
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}
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},
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no_op: () => {
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CPU.currentInstruction.mnemonic = `NOP`;
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CPU.IP += 2;
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},
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}
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const opcodes2mnemonics = {
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0: (operand) => Instructions.end(),
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1: (operand) => Instructions.store_lit(operand),
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2: (operand) => Instructions.store_addr(operand),
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3: (operand) => Instructions.load_lit(operand),
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4: (operand) => Instructions.load_addr(operand),
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5: (operand) => Instructions.add_lit(operand),
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6: (operand) => Instructions.add_addr(operand),
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7: (operand) => Instructions.sub_lit(operand),
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8: (operand) => Instructions.sub_addr(operand),
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9: (operand) => Instructions.hop_lit(operand),
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10: (operand) => Instructions.hop_addr(operand),
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11: (operand) => Instructions.jump_lit(operand),
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12: (operand) => Instructions.jump_addr(operand),
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13: (operand) => Instructions.flag_toggle(operand),
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14: (operand) => Instructions.flag_hop(operand),
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15: (operand) => Instructions.no_op(),
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};
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/**
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* Load code into memory and set CPU state to "running"
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* @param {Uint8Array} code - Machine code to load
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**/
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function startCPU(code) {
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CPU.loadMemory(code);
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CPU.running = true;
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}
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/**
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* Execute just the next instruction in memory
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**/
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function stepCPU() {
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CPU.currentInstruction.opcode = CPU.memory[CPU.IP];
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CPU.currentInstruction.operand = CPU.memory[CPU.IP+1];
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let executeInstruction = opcodes2mnemonics[CPU.currentInstruction.opcode];
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executeInstruction(CPU.currentInstruction.operand);
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}
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/**
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* @param {Uint8Array} code - Machine code to run
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* @param {Boolean} [debug] - Enable/disable debugging printouts
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**/
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exports.runProgram = async (code, debug = false) => {
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startCPU(code);
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let step = 0;
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while (true) {
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step = step + 1;
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if (CYCLE_LIMIT && (step > CYCLE_LIMIT)) { break; } // Temporary limit as a lazy way to halt infinite loops:
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if (!CPU.running) break;
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if (CPU.IP >= CPU.memory.length) break;
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stepCPU();
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await logCPUState(debug);
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};
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}
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// FUNCTIONS THAT PULL INFO FROM STATE TO DISPLAY
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/**
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* @param {Boolean} [debug] - Enable/disable debugging printouts
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**/
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async function logCPUState(debug = false) {
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console.group(`Step`);
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if (!debug) console.clear();
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if (debug) {
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display.printDisplay(CPU.memory);
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} else {
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display.prettyPrintDisplay(CPU.memory);
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}
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console.log();
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console.log('Mnemonic:', CPU.currentInstruction.mnemonic);
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console.log(`Machine: $${num2hex(CPU.currentInstruction.opcode)} $${num2hex(CPU.currentInstruction.operand)}`);
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console.log();
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console.log(`IP: $${num2hex(CPU.IP)} Acc: $${num2hex(CPU.Acc)} FLAGS: ${num2bin_4bit(CPU.FLAGS)} ${CPU.running ? "running" : "halted" }`);
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console.log();
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// Pause to show animated display:
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if (!debug) await new Promise(resolve => setTimeout(resolve, 75));
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console.groupEnd();
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}; |