Emulator: Add opcode $a8/$af

src/cpu.cpp

@@ -57,33 +57,45 @@ void CPU::update()
 	m_wait_cycles--;
 	if (m_wait_cycles <= 0) {
 		// Read next opcode
-		uint8_t opcode = peekMemory();
+		uint8_t opcode = read(m_pc);
+		print("running opcode: {:#x}\n", opcode);
 		switch (opcode) {
+
 		case 0x01: ld16(); break;
+		case 0x02: ld8(); break;
+		case 0x06: ld8(); break;
 		case 0x08: ld16(); break;
 		case 0x11: ld16(); break;
+		case 0x12: ld8(); break;
+		case 0x16: ld8(); break;
 		case 0x21: ld16(); break;
+		case 0x22: ld8(); break;
+		case 0x26: ld8(); break;
 		case 0x31: ld16(); break;
+		case 0x32: ld8(); break;
+		case 0x36: ld8(); break;
 		case 0x3e: ld8(); break;
+		case 0xa8: xor8(); break;
+		case 0xaf: xor8(); break;
 		case 0xc3: jp16(); break;
 		case 0xc6: add(); break;
+		case 0xcd: call(); break;
 		case 0xe0: ldh8(); break;
 		case 0xf0: ldh8(); break;
 		case 0xf8: ld16(); break;
 		case 0xf9: ld16(); break;
+
 		default:
-			print("opcode {:#x} not implemented", opcode);
+			print("opcode {:#x} not implemented\n", opcode);
 			VERIFY_NOT_REACHED();
 		}
 	}
-
-	// print("This is an update from the CPU\n");
 }
 
 void CPU::add()
 {
-	uint8_t opcode = consumeMemory();
+	uint8_t opcode = pcRead();
-	uint8_t immediate = consumeMemory();
+	uint8_t immediate = pcRead();
 	switch (opcode) {
 	case 0xc6:
 		// ADD A,d8
@@ -99,7 +111,28 @@ void CPU::add()
 		m_a += immediate;
 
 		// Drop overflown bits, the 'A' register is 8-bit
-		m_a &= 0xff;
+		m_a &= 0x00ff;
+		break;
+	default:
+		VERIFY_NOT_REACHED();
+	}
+}
+
+void CPU::xor8()
+{
+	uint8_t opcode = pcRead();
+	switch (opcode) {
+	case 0xa8:
+		// XOR B, flags: Z 0 0 0
+		m_nf = m_hf = m_cf = 0;
+		m_a ^= m_b;
+		m_zf = m_a == 0;
+		break;
+	case 0xaf:
+		// XOR A, flags: 1 0 0 0
+		// A^A will always be 0
+		m_a = m_nf = m_hf = m_cf = 0;
+		m_zf = 1;
 		break;
 	default:
 		VERIFY_NOT_REACHED();
@@ -108,11 +141,70 @@ void CPU::add()
 
 void CPU::ld8()
 {
-	uint8_t opcode = consumeMemory();
+	uint8_t opcode = pcRead();
 	switch (opcode) {
-	case 0x3e:
+	case 0x02:
+		// LD (BC),A
 		m_wait_cycles += 8;
-		m_a = immediate8();
+		write(bc(), m_a);
+		break;
+	case 0x06:
+		// LD B,n
+		m_wait_cycles += 8;
+		m_b = pcRead();
+		break;
+	case 0x12:
+		// LD (DE),A
+		m_wait_cycles += 8;
+		write(de(), m_a);
+		break;
+	case 0x16:
+		// LD D,n
+		m_wait_cycles += 8;
+		m_d = pcRead();
+		break;
+	case 0x22: {
+		// LD (HL+),A == LD (HLI),A == LDI (HL),A
+		m_wait_cycles += 8;
+
+		// Put A into memory address in HL
+		uint32_t address = hl();
+		write(address, m_a);
+
+		// Increment HL
+		address = (address + 1) & 0xffff;
+		m_l = address & 0x00ff;
+		m_h = address >> 8;
+		break;
+	}
+	case 0x26:
+		// LD H,n
+		m_wait_cycles += 8;
+		m_h = pcRead();
+		break;
+	case 0x32: {
+		// LD (HL-),A == LD (HLD),A == LDD (HL),A
+		m_wait_cycles += 8;
+
+		// Put A into memory address in HL
+		uint32_t address = hl();
+		write(address, m_a);
+
+		// Decrement HL
+		address = (address - 1) & 0xffff;
+		m_l = address & 0x00ff;
+		m_h = address >> 8;
+		break;
+	}
+	case 0x36:
+		// LD (HL),n
+		m_wait_cycles += 12;
+		write(hl(), pcRead());
+		break;
+	case 0x3e:
+		// LD A,n
+		m_wait_cycles += 8;
+		m_a = pcRead();
 		break;
 	default:
 		VERIFY_NOT_REACHED();
@@ -121,19 +213,21 @@ void CPU::ld8()
 
 void CPU::ldh8()
 {
-	uint8_t opcode = consumeMemory();
+	uint8_t opcode = pcRead();
 	switch (opcode) {
 	case 0xe0:
 		// LD ($ff00 + n),A == LDH (n),A
-		// Put value in A into address (0xff00 + next byte in memory):
 		m_wait_cycles += 12;
-		writeFf(m_a);
+
+		// Put value in A into address (0xff00 + next byte in memory)
+		ffWrite(pcRead(), m_a);
 		break;
 	case 0xf0:
 		// LD A,($ff00 + n) == LDH A,(n)
-		// Put value at address (0xff00 + next byte in memory) into A:
 		m_wait_cycles += 12;
-		m_a = readFf();
+
+		// Put value at address (0xff00 + next byte in memory) into A
+		m_a = ffRead(pcRead());
 		break;
 	default:
 		VERIFY_NOT_REACHED();
@@ -142,38 +236,50 @@ void CPU::ldh8()
 
 void CPU::ld16()
 {
-	uint8_t opcode = consumeMemory();
+	uint8_t opcode = pcRead();
 	switch (opcode) {
 	case 0x01: {
 		m_wait_cycles += 12;
-		setBc(immediate16());
+		write(bc(), pcRead16());
-		break;
-	}
-	case 0x11:
-		m_wait_cycles += 12;
-		setDe(immediate16());
-		break;
-	case 0x21:
-		m_wait_cycles += 12;
-		setHl(immediate16());
-		break;
-	case 0x31: {
-		m_wait_cycles += 12;
-		m_sp = immediate16();
 		break;
 	}
 	case 0x08: {
+		// LD (nn),SP
 		m_wait_cycles += 20;
+
+		// Put value of SP into address given by next 2 bytes in memory
 		// TODO
 		break;
 	}
-	case 0xf8: {
+	case 0x11:
+		// LD DE,nn
 		m_wait_cycles += 12;
+		write(de(), pcRead16());
+		break;
+	case 0x21:
+		// LD HL,nn
+		m_wait_cycles += 12;
+		write(hl(), pcRead16());
+		break;
+	case 0x31: {
+		// LD SP,nn
+		m_wait_cycles += 12;
+		m_sp = pcRead16();
+		break;
+	}
+	case 0xf8: {
+		// LD HL,SP + e8 == LDHL SP,e8
+		m_wait_cycles += 12;
+
+		// Put SP + next (signed) byte in memory into HL
 		// TODO
+
+		// Unsets ZF and NF, may enable HF and CF
 		// TODO flags
 		break;
 	}
 	case 0xf9: {
+		// LD SP,HL
 		m_wait_cycles += 8;
 		m_sp = hl();
 		break;
@@ -183,13 +289,39 @@ void CPU::ld16()
 	}
 }
 
+void CPU::call()
+{
+	uint8_t opcode = pcRead();
+	switch (opcode) {
+	case 0xcd: {
+		// CALL nn
+		m_wait_cycles += 24;
+
+		uint32_t data = pcRead16();
+
+		// Push address of next 2 bytes in memory onto stack
+		m_sp = (m_sp - 1) & 0xffff;
+		write(m_sp, data >> 8);
+		m_sp = (m_sp - 1) & 0xffff;
+		write(m_sp, data & 0x00ff);
+
+		// Jump to this address
+		m_pc = data;
+		break;
+	}
+	default:
+		VERIFY_NOT_REACHED();
+	}
+}
+
 void CPU::jp16()
 {
-	uint8_t opcode = consumeMemory();
+	uint8_t opcode = pcRead();
 	switch (opcode) {
 	case 0xc3:
+		// JP nn
 		m_wait_cycles += 16;
-		m_pc = immediate16();
+		m_pc = pcRead16();
 		break;
 	default:
 		VERIFY_NOT_REACHED();
@@ -198,40 +330,29 @@ void CPU::jp16()
 
 // -----------------------------------------
 
-uint8_t CPU::peekMemory(int32_t offset) const
+uint32_t CPU::pcRead()
 {
-	return Emu::the().readMemory(m_pc + offset);
+	uint32_t data = Emu::the().readMemory(m_pc);
+	m_pc = (m_pc + 1) & 0xffff;
+	return data;
 }
 
-uint8_t CPU::consumeMemory()
+void CPU::write(uint32_t address, uint32_t value)
 {
-	return Emu::the().readMemory(m_pc++);
+	Emu::the().writeMemory(address, value);
 }
 
-void CPU::writeFf(uint32_t value)
+uint32_t CPU::read(uint32_t address)
 {
-	Emu::the().writeMemory(immediate8() | (0xff << 8), value);
+	return Emu::the().readMemory(address);
 }
 
-uint32_t CPU::readFf()
+void CPU::ffWrite(uint32_t address, uint32_t value)
 {
-	return Emu::the().readMemory(immediate8() | (0xff << 8));
+	Emu::the().writeMemory(address | (0xff << 8), value);
 }
 
-void CPU::setBc(uint32_t value)
+uint32_t CPU::ffRead(uint32_t address)
 {
-	m_b = value >> 8;
+	return Emu::the().readMemory(address | (0xff << 8));
-	m_c = value;
-}
-
-void CPU::setDe(uint32_t value)
-{
-	m_d = value >> 8;
-	m_e = value;
-}
-
-void CPU::setHl(uint32_t value)
-{
-	m_h = value >> 8;
-	m_l = value;
 }

src/cpu.h

@@ -25,6 +25,7 @@ public:
 
 	// 8-bit
 	void add();
+	void xor8();
 
 	// 16-bit
 
@@ -47,6 +48,7 @@ public:
 	// -------------------------------------
 	// Jumps and Subroutines
 
+	void call();
 	void jp16();
 
 	// -------------------------------------
@@ -56,18 +58,14 @@ public:
 	// Miscellaneous Instructions
 
 private:
-	uint8_t peekMemory(int32_t offset = 0) const;
+	uint32_t pcRead();
-	uint8_t consumeMemory();
+	uint32_t pcRead16() { return pcRead() | (pcRead() << 8); }
 
-	uint32_t immediate8() { return consumeMemory(); }
+	void write(uint32_t address, uint32_t value);
-	uint32_t immediate16() { return consumeMemory() | (consumeMemory() << 8); }
+	uint32_t read(uint32_t address);
 
-	void writeFf(uint32_t value);
+	void ffWrite(uint32_t address, uint32_t value);
-	uint32_t readFf();
+	uint32_t ffRead(uint32_t address);
-
-	void setBc(uint32_t value);
-	void setDe(uint32_t value);
-	void setHl(uint32_t value);
 
 	uint32_t bc() const { return m_b << 8 | m_c; }
 	uint32_t de() const { return m_b << 8 | m_c; }