Did some instructions

src/cpu.ts

@@ -101,15 +101,150 @@ class CPU {
 	private cycle() {
 		// Fetch opcode
 		let firstOpcode: number = this.memory[this.pc];
-		let secondtOpcode: number = this.memory[this.pc + 1];
-		let opcode: number = firstOpcode << 8 | secondtOpcode;
+		let secondOpcode: number = this.memory[this.pc + 1];
+		let opcode: number = firstOpcode << 8 | secondOpcode;
 		
 		// Decode opcode
-
-		let firstNibble = opcode >> 12;
+		// X000
+		let firstNibble = firstOpcode >> 4;
 		
 		switch(firstNibble) {
+			case 0x0: 
+				if(opcode == 0x00E0) {
+					// Clear the screen
+					this.clearDisplay();
+				}else if(opcode == 0x00EE) {
+					// Returns from a subroutine
+					this.stackPointer--;
+					this.pc = this.stack[this.pc];
+				}
+				this.incrementPC();
+				break;
+			case 0x1:
+				// goto NNN;
+				let threeNib = opcode & 0x0FFF;
+				this.pc = threeNib;
+				break;
+			case 0x2:
+				// Calls subroutine at NNN
+				this.stack[this.stackPointer] = this.pc; // Store PC at stack
+				this.stackPointer++;	// Increment it
+				this.pc = opcode & 0x0FFF; // Go to that address to execute code
+				break;
+			case 0x3: {
+				// 3XNN
+				// Skips the next instruction if VX equals NN
+				let secondNibble = firstOpcode & 0xF; //0X00
+				let val = opcode & 0x00FF; //0x00NN
+				if(this.registers[secondNibble] == val){
+					this.incrementPC();
+				}
+				this.incrementPC();
+				}
+				break;
+			case 0x4: {
+				// 4XNN
+				// Skips the next instruction if VX NOT equals NN
+				let secondNibble = firstOpcode & 0xF; //0X00
+				let val = opcode & 0x00FF; //0x00NN
+				if(this.registers[secondNibble] != val){
+					this.incrementPC();
+				}
+				this.incrementPC();
+				}
+				break;
+			case 0x5: {
+				// 5XY0
+				// Skips the next instruction if VX == VY
+				let secondNibble = firstOpcode & 0xF; //0X00
+				let thirdNibble = secondOpcode >> 4; //00Y0
+				if(this.registers[secondNibble] == this.registers[thirdNibble]) {
+					this.incrementPC();
+				}
+				this.incrementPC();
+				}
+				break;
+			case 0x6: {
+				// 6XNN
+				// Sets VX to NN
+				let secondNibble = firstOpcode & 0xF; //0X00
+				this.registers[secondNibble] = secondOpcode;
+				this.incrementPC();
+				}
+				break;
+			case 0x7: {
+				// 7XNN
+				// Adds NN to VX
+				let secondNibble = firstOpcode & 0xF; //0X00
+				this.registers[secondNibble] = secondOpcode;
+				this.incrementPC();
+				}
+				break;
+			case 0x8: {
+				let secondNibble = firstOpcode & 0xF; //0X00
+				let thirdNibble = secondOpcode >> 4; //00Y0
+				let lastNibble = secondOpcode & 0xF; //000N
+				if(lastNibble == 0x0) {
+					// 8XY0
+					// Vx |= Vy
+					this.registers[secondNibble] = this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0x1) {
+					// 8XY1
+					// Vx |= Vy
+					this.registers[secondNibble] |= this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0x2) {
+					// 8XY2
+					// Vx &= Vy
+					this.registers[secondNibble] &= this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0x3) {
+					// 8XY3
+					// Vx ^= Vy
+					this.registers[secondNibble] ^= this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0x4) {
+					// 8XY4
+					// Vx += Vy
+					let sum = this.registers[secondNibble] + this.registers[thirdNibble];
+					this.registers[0xF] = sum > 255 ? 1 : 0; // Set carry flag
+					this.registers[secondNibble] = sum & 0xFF; // Get only the first byte
+					this.incrementPC();
+				}else if(lastNibble == 0x5) {
+					// 8XY5
+					// Vx -= Vy
+					this.registers[0xF] = this.registers[secondNibble] > this.registers[thirdNibble] ? 1 : 0;
+					let subs = this.registers[secondNibble] - this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0x6) {
+					// 8XY6
+					// Vx >>= 1
+					this.registers[secondNibble] >> 1;
+					this.incrementPC();
+				}else if(lastNibble == 0x7) {
+					// 8XY7
+					// Vx = Vy - Vx
+					this.registers[0xF] = this.registers[secondNibble] > this.registers[thirdNibble] ? 1 : 0;
+					let subs = this.registers[secondNibble] - this.registers[thirdNibble];
+					this.incrementPC();
+				}else if(lastNibble == 0xE) {
 
+				}
+
+				}
+				break;
+			case 0x9: {
+				// 9XY0
+				// Skips the next instruction if VX != VY
+				let secondNibble = firstOpcode & 0xF; //0X00
+				let thirdNibble = secondOpcode >> 4; //00Y0
+				if(this.registers[secondNibble] != this.registers[thirdNibble]) {
+					this.incrementPC();
+				}
+				this.incrementPC();
+				}
+				break;
 		}
 	}