From 00850645cdd12565dc0ce62465ef5741c70bb71a Mon Sep 17 00:00:00 2001
From: EliseZeroTwo <mail@elise.moe>
Date: Sun, 19 Dec 2021 12:27:41 +0100
Subject: [PATCH] feat: fix a few instructions, add halt

---
 deemgee-opcode/src/lib.rs                  |   7 +-
 deemgee/src/gameboy.rs                     |  17 +-
 deemgee/src/gameboy/cpu.rs                 |  52 ++-
 deemgee/src/gameboy/cpu/alu.rs             |  68 ++--
 deemgee/src/gameboy/cpu/flow.rs            |   5 +-
 deemgee/src/gameboy/cpu/load_store_move.rs |  49 +++
 deemgee/src/gameboy/cpu/misc.rs            |  16 +-
 deemgee/src/gameboy/cpu/prefixed.rs        | 410 ++++++++++++++++++++-
 deemgee/src/gameboy/interrupts.rs          |  10 +-
 deemgee/src/gameboy/joypad.rs              |  24 ++
 deemgee/src/gameboy/mapper.rs              |   2 +
 deemgee/src/gameboy/mapper/mbc1.rs         | 114 ++++++
 deemgee/src/gameboy/ppu.rs                 |   8 +-
 deemgee/src/gameboy/serial.rs              |  22 +-
 deemgee/src/gameboy/timer.rs               |   4 +-
 deemgee/src/main.rs                        |  18 +-
 16 files changed, 766 insertions(+), 60 deletions(-)
 create mode 100644 deemgee/src/gameboy/mapper/mbc1.rs

diff --git a/deemgee-opcode/src/lib.rs b/deemgee-opcode/src/lib.rs
index 7334cd5..9655432 100644
--- a/deemgee-opcode/src/lib.rs
+++ b/deemgee-opcode/src/lib.rs
@@ -87,13 +87,15 @@ pub fn opcode(item: TokenStream) -> TokenStream {
 	let log = if extended.value {
 		quote::quote! {
 			if state.registers.cycle == 1 && state.log_instructions {
-				log::debug!("Prefixed OP {} ({:#02X})", #readable, #opcode);
+				log::debug!("(PC: {:#02X}) Prefixed OP {} ({:#02X})", state.registers.pc, #readable, #opcode);
+				#regs
 			}
 		}
 	} else {
 		quote::quote! {
 			if state.registers.cycle == 0 && state.log_instructions {
-				log::debug!("OP {} ({:#02X})", #readable, #opcode);
+				log::debug!("(PC: {:#02X}) OP {} ({:#02X})", state.registers.pc, #readable, #opcode);
+				#regs
 			}
 		}
 	};
@@ -101,7 +103,6 @@ pub fn opcode(item: TokenStream) -> TokenStream {
 	let out = quote::quote! {
 		#fn_sig {
 			#log
-			#regs
 
 			#match_statement
 		}
diff --git a/deemgee/src/gameboy.rs b/deemgee/src/gameboy.rs
index c58746f..cef02cf 100644
--- a/deemgee/src/gameboy.rs
+++ b/deemgee/src/gameboy.rs
@@ -15,7 +15,12 @@ use memory::Memory;
 use ppu::Ppu;
 use timer::Timer;
 
-use self::{cpu::Registers, mapper::NoMBC, serial::Serial, sound::Sound};
+use self::{
+	cpu::Registers,
+	mapper::{mbc1::MBC1, NoMBC},
+	serial::Serial,
+	sound::Sound,
+};
 
 pub struct DmaState {
 	pub base: u8,
@@ -53,6 +58,9 @@ pub struct Gameboy {
 	pub mem_write_breakpoints: [bool; u16::MAX as usize + 1],
 	trigger_bp: bool,
 	pub log_instructions: bool,
+	pub halt: bool,
+	pub halt_bug: bool,
+	pub used_halt_bug: bool,
 }
 
 impl Gameboy {
@@ -74,6 +82,9 @@ impl Gameboy {
 			mem_write_breakpoints: [false; u16::MAX as usize + 1],
 			trigger_bp: false,
 			log_instructions: false,
+			halt: false,
+			halt_bug: false,
+			used_halt_bug: false,
 		}
 	}
 
@@ -100,6 +111,7 @@ impl Gameboy {
 	pub fn load_cartridge(&mut self, bytes: Vec<u8>) {
 		match bytes[0x147] {
 			0 => self.cartridge = Some(Box::new(NoMBC::new(bytes))),
+			1 => self.cartridge = Some(Box::new(MBC1::new(bytes))),
 			other => unimplemented!("Cartidge type: {:#X}", other),
 		}
 	}
@@ -235,6 +247,9 @@ impl Gameboy {
 		cpu::tick_cpu(self);
 		let redraw_requested = self.ppu.tick(&mut self.interrupts);
 		self.tick_dma();
+		if self.serial.tick() {
+			self.interrupts.write_if_serial(true);
+		}
 		redraw_requested
 	}
 
diff --git a/deemgee/src/gameboy/cpu.rs b/deemgee/src/gameboy/cpu.rs
index 5ed2e74..ea3fc2d 100644
--- a/deemgee/src/gameboy/cpu.rs
+++ b/deemgee/src/gameboy/cpu.rs
@@ -104,6 +104,24 @@ impl Registers {
 pub fn tick_cpu(state: &mut Gameboy) {
 	state.registers.mem_op_happened = false;
 
+	if state.joypad.interrupt_triggered {
+		state.joypad.interrupt_triggered = false;
+		state.interrupts.write_if_joypad(true);
+	}
+
+	if state.registers.cycle == 0 && state.halt {
+		if (state.interrupts.read_ie_vblank() && state.interrupts.read_if_vblank())
+			|| (state.interrupts.read_ie_lcd_stat() && state.interrupts.read_if_lcd_stat())
+			|| (state.interrupts.read_ie_timer() && state.interrupts.read_if_timer())
+			|| (state.interrupts.read_ie_serial() && state.interrupts.read_if_serial())
+			|| (state.interrupts.read_ie_joypad() && state.interrupts.read_if_joypad())
+		{
+			state.halt = false;
+		} else {
+			return;
+		}
+	}
+
 	// TODO: Interrupts
 	if state.registers.cycle == 0 && state.interrupts.ime {
 		if state.interrupts.read_ie_vblank() && state.interrupts.read_if_vblank() {
@@ -129,6 +147,17 @@ pub fn tick_cpu(state: &mut Gameboy) {
 		}
 	}
 
+	if state.registers.cycle == 0 && state.interrupts.ei_queued {
+		state.interrupts.ime = state.interrupts.ei_queued;
+		state.interrupts.ei_queued = false;
+	}
+
+	if state.registers.cycle == 0 && state.halt_bug {
+		state.used_halt_bug = true;
+		state.halt_bug = false;
+		state.registers.pc = state.registers.pc.overflowing_sub(1).0;
+	}
+
 	let result = if let Some(idx) = state.registers.in_interrupt_vector {
 		match state.registers.cycle {
 			0 => {
@@ -138,11 +167,11 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			}
 			1 => CycleResult::NeedsMore,
 			2 => {
-				state.cpu_push_stack((state.registers.pc.overflowing_add(3).0 >> 8) as u8);
+				state.cpu_push_stack((state.registers.pc >> 8) as u8);
 				CycleResult::NeedsMore
 			}
 			3 => {
-				state.cpu_push_stack(state.registers.pc.overflowing_add(3).0 as u8);
+				state.cpu_push_stack(state.registers.pc as u8);
 				CycleResult::NeedsMore
 			}
 			4 => {
@@ -179,6 +208,7 @@ pub fn tick_cpu(state: &mut Gameboy) {
 		let result: CycleResult = match opcode {
 			0x00 => misc::nop,
 			0x01 => load_store_move::ld_bc_imm_u16,
+			0x02 => load_store_move::ld_deref_bc_a,
 			0x03 => alu::inc_bc,
 			0x04 => alu::inc_b,
 			0x05 => alu::dec_b,
@@ -191,6 +221,7 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0x0d => alu::dec_c,
 			0x0e => load_store_move::ld_c_imm_u8,
 			0x11 => load_store_move::ld_de_imm_u16,
+			0x12 => load_store_move::ld_deref_de_a,
 			0x13 => alu::inc_de,
 			0x14 => alu::inc_d,
 			0x15 => alu::dec_d,
@@ -203,6 +234,7 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0x1c => alu::inc_e,
 			0x1d => alu::dec_e,
 			0x1e => load_store_move::ld_e_imm_u8,
+			0x1f => alu::rra,
 			0x20 => flow::jr_nz_i8,
 			0x21 => load_store_move::ld_hl_imm_u16,
 			0x22 => load_store_move::ld_hl_plus_a,
@@ -288,6 +320,7 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0x73 => load_store_move::ld_deref_hl_e,
 			0x74 => load_store_move::ld_deref_hl_h,
 			0x75 => load_store_move::ld_deref_hl_l,
+			0x76 => misc::halt,
 			0x77 => load_store_move::ld_deref_hl_a,
 			0x78 => load_store_move::ld_a_b,
 			0x79 => load_store_move::ld_a_c,
@@ -380,6 +413,7 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0xD0 => flow::ret_nc,
 			0xD1 => load_store_move::pop_de,
 			0xD2 => flow::jp_nc_u16,
+			0xD3 => panic!("Executing bad opcode {:#02X}", opcode),
 			0xD4 => flow::call_nc_u16,
 			0xD5 => load_store_move::push_de,
 			0xD6 => alu::sub_a_imm_u8,
@@ -387,17 +421,21 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0xD8 => flow::ret_c,
 			0xD9 => flow::reti,
 			0xDA => flow::jp_c_u16,
+			0xDB => panic!("Executing bad opcode {:#02X}", opcode),
 			0xDC => flow::call_c_u16,
+			0xDD => panic!("Executing bad opcode {:#02X}", opcode),
 			0xDE => alu::sbc_a_imm_u8,
 			0xDF => flow::rst_0x18,
 			0xE0 => load_store_move::ldh_imm_u8_a,
 			0xE1 => load_store_move::pop_hl,
 			0xE2 => load_store_move::ldh_deref_c_a,
+			0xE3 | 0xE4 => panic!("Executing bad opcode {:#02X}", opcode),
 			0xE5 => load_store_move::push_hl,
 			0xE6 => alu::and_a_imm_u8,
 			0xE7 => flow::rst_0x20,
 			0xE9 => flow::jp_hl,
 			0xEA => load_store_move::ld_deref_imm_u16_a,
+			0xEB | 0xEC | 0xED => panic!("Executing bad opcode {:#02X}", opcode),
 			0xEE => alu::xor_a_imm_u8,
 			0xEF => flow::rst_0x28,
 			0xF0 => load_store_move::ldh_a_imm_u8,
@@ -407,9 +445,11 @@ pub fn tick_cpu(state: &mut Gameboy) {
 			0xF5 => load_store_move::push_af,
 			0xF6 => alu::or_a_imm_u8,
 			0xF7 => flow::rst_0x30,
+			0xF8 => load_store_move::ld_hl_sp_i8,
 			0xF9 => load_store_move::ld_sp_hl,
 			0xFA => load_store_move::ld_a_deref_imm_u16,
 			0xFB => misc::ei,
+			0xFC | 0xFD => panic!("Executing bad opcode {:#02X}", opcode),
 			0xFE => alu::cp_a_imm_u8,
 			0xFF => flow::rst_0x38,
 			unknown => {
@@ -425,13 +465,16 @@ pub fn tick_cpu(state: &mut Gameboy) {
 	};
 
 	if result == CycleResult::Finished {
+		if state.used_halt_bug {
+			state.registers.pc = state.registers.pc.overflowing_add(1).0;
+		}
+
 		match state.registers.opcode_bytecount {
-			Some(len) => state.registers.pc += len as u16,
+			Some(len) => state.registers.pc = state.registers.pc.overflowing_add(len as u16).0,
 			None => panic!("Forgot to set opcode len"),
 		}
 
 		if !state.registers.mem_op_happened {
-			log::trace!("Memory bus clear, precaching next opcode");
 			state.cpu_read_u8(state.registers.pc);
 		}
 
@@ -439,7 +482,6 @@ pub fn tick_cpu(state: &mut Gameboy) {
 		state.registers.current_prefixed_opcode = None;
 		state.registers.current_opcode = None;
 		state.registers.opcode_bytecount = None;
-		log::trace!("Cycle finished");
 	} else {
 		state.registers.cycle += 1;
 	}
diff --git a/deemgee/src/gameboy/cpu/alu.rs b/deemgee/src/gameboy/cpu/alu.rs
index 263f4d3..fca8aa1 100644
--- a/deemgee/src/gameboy/cpu/alu.rs
+++ b/deemgee/src/gameboy/cpu/alu.rs
@@ -17,12 +17,7 @@ pub fn sub_with_carry(lhs: u8, rhs: u8, carry: bool) -> CarryResult {
 	let (result, second_carry) = first_res.overflowing_sub(carry_u8);
 
 	let carry = first_carry || second_carry;
-
-	let first_hc_res = (lhs & 0xF).overflowing_sub(rhs & 0xF).0;
-	let first_half_carry = (first_hc_res >> 4) & 0b1 == 1;
-	let second_half_carry = ((first_hc_res.overflowing_sub(carry_u8).0) >> 4) & 0b1 == 1;
-
-	let half_carry = first_half_carry || second_half_carry;
+	let half_carry = (lhs & 0xF) < (rhs & 0xF) + carry_u8;
 
 	CarryResult { result, carry, half_carry }
 }
@@ -34,26 +29,21 @@ pub fn add_with_carry(lhs: u8, rhs: u8, carry: bool) -> CarryResult {
 	let (result, second_carry) = first_res.overflowing_add(carry_u8);
 
 	let carry = first_carry || second_carry;
-
-	let first_hc_res = (lhs & 0xF) + (rhs & 0xF);
-	let first_half_carry = (first_hc_res >> 4) & 0b1 == 1;
-	let second_half_carry = ((first_hc_res + carry_u8) >> 4) & 0b1 == 1;
-
-	let half_carry = first_half_carry || second_half_carry;
+	let half_carry = (lhs & 0xF) + (rhs & 0xF) > 0xF;
 
 	CarryResult { result, carry, half_carry }
 }
 
 pub fn add(lhs: u8, rhs: u8) -> CarryResult {
 	let (result, carry) = lhs.overflowing_add(rhs);
-	let half_carry = (((lhs & 0xF) + (rhs & 0xF)) >> 4) & 0b1 == 1;
+	let half_carry = (lhs & 0xF) + (rhs & 0xF) > 0xF;
 
 	CarryResult { result, carry, half_carry }
 }
 
 pub fn sub(lhs: u8, rhs: u8) -> CarryResult {
 	let (result, carry) = lhs.overflowing_sub(rhs);
-	let half_carry = (((lhs & 0xF).overflowing_sub(rhs & 0xF).0) >> 4) & 0b1 == 1;
+	let half_carry = (lhs & 0xF) < (rhs & 0xF);
 
 	CarryResult { result, carry, half_carry }
 }
@@ -511,6 +501,25 @@ opcode!(rla, 0x17, "RLA", false, {
 	}
 });
 
+opcode!(rra, 0x1f, "RRA", false, {
+	0 => {
+		let carry = state.registers.a & 0b1 == 1;
+		state.registers.a >>= 1;
+
+		if state.registers.get_carry() {
+			state.registers.a = state.registers.a.wrapping_add(1 << 7);
+		}
+
+		state.registers.set_zero(false);
+		state.registers.set_subtract(false);
+		state.registers.set_half_carry(false);
+		state.registers.set_carry(carry);
+
+		state.registers.opcode_bytecount = Some(1);
+		CycleResult::Finished
+	}
+});
+
 macro_rules! define_inc_u16_reg {
 	($op:literal, $lreg:ident, $rreg:ident) => {
 		paste::paste! {
@@ -818,15 +827,18 @@ macro_rules! define_add_hl_u16_reg {
 					CycleResult::NeedsMore
 				},
 				1 => {
+					let CarryResult { result, carry, half_carry } = add(state.registers.h, state.registers.$lreg);
+					state.registers.h = result;
+					state.registers.set_half_carry(half_carry);
+					state.registers.set_carry(carry);
+
 					if state.registers.take_hold() != 0 {
-						let CarryResult { result, carry, half_carry } = add(state.registers.h, state.registers.$lreg);
+						let CarryResult { result, carry: s_carry, half_carry: s_half_carry } = add(state.registers.h, 1);
 						state.registers.h = result;
-						state.registers.set_half_carry(half_carry);
-						state.registers.set_carry(carry);
-					} else {
-						state.registers.set_half_carry(false);
-						state.registers.set_carry(false);
+						state.registers.set_half_carry(half_carry || s_half_carry);
+						state.registers.set_carry(carry || s_carry);
 					}
+
 					state.registers.set_subtract(false);
 					state.registers.opcode_bytecount = Some(1);
 					CycleResult::Finished
@@ -848,16 +860,18 @@ opcode!(add_hl_sp, 0x39, "ADD HL, SP", false, {
 		CycleResult::NeedsMore
 	},
 	1 => {
+		let CarryResult { result, carry, half_carry } = add(state.registers.h, (state.registers.sp >> 8) as u8);
+		state.registers.h = result;
+		state.registers.set_half_carry(half_carry);
+		state.registers.set_carry(carry);
+
 		if state.registers.take_hold() != 0 {
-			let CarryResult { result, carry, half_carry } =
-				add(state.registers.h, (state.registers.sp >> 8) as u8);
+			let CarryResult { result, carry: s_carry, half_carry: s_half_carry } = add(state.registers.h, 1);
 			state.registers.h = result;
-			state.registers.set_half_carry(half_carry);
-			state.registers.set_carry(carry);
-		} else {
-			state.registers.set_half_carry(false);
-			state.registers.set_carry(false);
+			state.registers.set_half_carry(half_carry || s_half_carry);
+			state.registers.set_carry(carry || s_carry);
 		}
+
 		state.registers.set_subtract(false);
 		state.registers.opcode_bytecount = Some(1);
 		CycleResult::Finished
diff --git a/deemgee/src/gameboy/cpu/flow.rs b/deemgee/src/gameboy/cpu/flow.rs
index 0561925..6cd213f 100644
--- a/deemgee/src/gameboy/cpu/flow.rs
+++ b/deemgee/src/gameboy/cpu/flow.rs
@@ -477,6 +477,7 @@ opcode!(ret, 0xC9, "RET", false, {
 	},
 	3 => {
 		let address = (state.registers.take_mem() as u16) << 8 | state.registers.take_hold();
+		println!("RET to {:#04X}", address);
 		state.registers.pc = address;
 		state.registers.opcode_bytecount = Some(0);
 		CycleResult::Finished
@@ -634,11 +635,11 @@ macro_rules! define_rst {
 					CycleResult::NeedsMore
 				},
 				1 => {
-					state.cpu_push_stack((state.registers.pc >> 8) as u8);
+					state.cpu_push_stack((state.registers.pc.overflowing_add(1).0 >> 8) as u8);
 					CycleResult::NeedsMore
 				},
 				2 => {
-					state.cpu_push_stack((state.registers.pc & 0xFF) as u8);
+					state.cpu_push_stack((state.registers.pc.overflowing_add(1).0 & 0xFF) as u8);
 					CycleResult::NeedsMore
 				},
 				3 => {
diff --git a/deemgee/src/gameboy/cpu/load_store_move.rs b/deemgee/src/gameboy/cpu/load_store_move.rs
index 10c841d..729e259 100644
--- a/deemgee/src/gameboy/cpu/load_store_move.rs
+++ b/deemgee/src/gameboy/cpu/load_store_move.rs
@@ -168,6 +168,28 @@ define_ld_reg_deref!(0x7E, a, hl);
 define_ld_reg_deref!(0x0A, a, bc);
 define_ld_reg_deref!(0x1A, a, de);
 
+opcode!(ld_deref_bc_a, 0x02, "LD (BC),A", false, {
+	0 => {
+		state.cpu_write_u8(state.registers.get_bc(), state.registers.a);
+		CycleResult::NeedsMore
+	},
+	1 => {
+		state.registers.opcode_bytecount = Some(1);
+		CycleResult::Finished
+	}
+});
+
+opcode!(ld_deref_de_a, 0x12, "LD (DE),A", false, {
+	0 => {
+		state.cpu_write_u8(state.registers.get_de(), state.registers.a);
+		CycleResult::NeedsMore
+	},
+	1 => {
+		state.registers.opcode_bytecount = Some(1);
+		CycleResult::Finished
+	}
+});
+
 opcode!(ld_hl_plus_a, 0x22, "LD (HL+),A", false, {
 	0 => {
 		state.cpu_write_u8(state.registers.get_hl(), state.registers.a);
@@ -222,6 +244,33 @@ opcode!(ld_a_hl_minus, 0x3A, "LD A,(HL-)", false, {
 	}
 });
 
+opcode!(ld_hl_sp_i8, 0xF8, "LD HL,SP+i8", false, {
+	0 => {
+		state.cpu_read_u8(state.registers.pc.overflowing_add(1).0);
+		CycleResult::NeedsMore
+	},
+	1 => {
+		let val = state.registers.take_mem() as i8;
+
+		let rhs = if val < 0 {
+			state.registers.sp.overflowing_sub((val as u8 & !(1u8 << 7)) as u16).0
+		} else {
+			state.registers.sp.overflowing_add(val as u16).0
+		};
+
+		state.registers.set_hl(rhs);
+		state.registers.set_zero(false);
+		state.registers.set_subtract(false);
+		state.registers.set_half_carry((state.registers.sp & 0xF) + (val as u16 & 0xF) > 0xF);
+		state.registers.set_carry((state.registers.sp & 0xFF) + (val as u16 & 0xFF) > 0xFF);
+		CycleResult::NeedsMore
+	},
+	2 => {
+		state.registers.opcode_bytecount = Some(2);
+		CycleResult::Finished
+	}
+});
+
 macro_rules! define_ld_reg_imm_u8 {
 	($op:literal, $lreg:ident) => {
 		paste::paste! {
diff --git a/deemgee/src/gameboy/cpu/misc.rs b/deemgee/src/gameboy/cpu/misc.rs
index 3396aec..345e028 100644
--- a/deemgee/src/gameboy/cpu/misc.rs
+++ b/deemgee/src/gameboy/cpu/misc.rs
@@ -12,7 +12,7 @@ opcode!(nop, 0x00, "NOP", false, {
 
 opcode!(di, 0xF3, "DI", false, {
 	0 => {
-		state.interrupts.ime = false;
+		state.interrupts.cpu_set_ime(false);
 		state.registers.opcode_bytecount = Some(1);
 		CycleResult::Finished
 	}
@@ -20,8 +20,20 @@ opcode!(di, 0xF3, "DI", false, {
 
 opcode!(ei, 0xFB, "EI", false, {
 		0 => {
-			state.interrupts.ime = true;
+			state.interrupts.cpu_set_ime(true);
 			state.registers.opcode_bytecount = Some(1);
 			CycleResult::Finished
 		}
 });
+
+opcode!(halt, 0x76, "HALT", false, {
+	0 => {
+		if !state.interrupts.ime && (state.interrupts.interrupt_enable & state.interrupts.interrupt_flag & 0x1F != 0) {
+			state.halt_bug = true;
+		} else {
+			state.halt = true;
+		}
+		state.registers.opcode_bytecount = Some(1);
+		CycleResult::Finished
+	}
+});
diff --git a/deemgee/src/gameboy/cpu/prefixed.rs b/deemgee/src/gameboy/cpu/prefixed.rs
index 71c5ca7..0ac5177 100644
--- a/deemgee/src/gameboy/cpu/prefixed.rs
+++ b/deemgee/src/gameboy/cpu/prefixed.rs
@@ -26,6 +26,13 @@ pub fn prefixed_handler(state: &mut Gameboy) -> CycleResult {
 		0x14 => rl_h,
 		0x15 => rl_l,
 		0x17 => rl_a,
+		0x18 => rr_b,
+		0x19 => rr_c,
+		0x1a => rr_d,
+		0x1b => rr_e,
+		0x1c => rr_h,
+		0x1d => rr_l,
+		0x1f => rr_a,
 		0x30 => swap_b,
 		0x31 => swap_c,
 		0x32 => swap_d,
@@ -33,6 +40,13 @@ pub fn prefixed_handler(state: &mut Gameboy) -> CycleResult {
 		0x34 => swap_h,
 		0x35 => swap_l,
 		0x37 => swap_a,
+		0x38 => srl_b,
+		0x39 => srl_c,
+		0x3a => srl_d,
+		0x3b => srl_e,
+		0x3c => srl_h,
+		0x3d => srl_l,
+		0x3f => srl_a,
 		0x40 => bit_0_b,
 		0x41 => bit_0_c,
 		0x42 => bit_0_d,
@@ -97,6 +111,134 @@ pub fn prefixed_handler(state: &mut Gameboy) -> CycleResult {
 		0x7d => bit_7_l,
 		0x7e => bit_7_deref_hl,
 		0x7f => bit_7_a,
+		0x80 => res_0_b,
+		0x81 => res_0_c,
+		0x82 => res_0_d,
+		0x83 => res_0_e,
+		0x84 => res_0_h,
+		0x85 => res_0_l,
+		0x86 => res_0_deref_hl,
+		0x87 => res_0_a,
+		0x88 => res_1_b,
+		0x89 => res_1_c,
+		0x8A => res_1_d,
+		0x8B => res_1_e,
+		0x8C => res_1_h,
+		0x8D => res_1_l,
+		0x8E => res_1_deref_hl,
+		0x8F => res_1_a,
+		0x90 => res_2_b,
+		0x91 => res_2_c,
+		0x92 => res_2_d,
+		0x93 => res_2_e,
+		0x94 => res_2_h,
+		0x95 => res_2_l,
+		0x96 => res_2_deref_hl,
+		0x97 => res_2_a,
+		0x98 => res_3_b,
+		0x99 => res_3_c,
+		0x9A => res_3_d,
+		0x9B => res_3_e,
+		0x9C => res_3_h,
+		0x9D => res_3_l,
+		0x9E => res_3_deref_hl,
+		0x9F => res_3_a,
+		0xA0 => res_4_b,
+		0xA1 => res_4_c,
+		0xA2 => res_4_d,
+		0xA3 => res_4_e,
+		0xA4 => res_4_h,
+		0xA5 => res_4_l,
+		0xA6 => res_4_deref_hl,
+		0xA7 => res_4_a,
+		0xA8 => res_5_b,
+		0xA9 => res_5_c,
+		0xAA => res_5_d,
+		0xAB => res_5_e,
+		0xAC => res_5_h,
+		0xAD => res_5_l,
+		0xAE => res_5_deref_hl,
+		0xAF => res_5_a,
+		0xB0 => res_6_b,
+		0xB1 => res_6_c,
+		0xB2 => res_6_d,
+		0xB3 => res_6_e,
+		0xB4 => res_6_h,
+		0xB5 => res_6_l,
+		0xB6 => res_6_deref_hl,
+		0xB7 => res_6_a,
+		0xB8 => res_7_b,
+		0xB9 => res_7_c,
+		0xBA => res_7_d,
+		0xBB => res_7_e,
+		0xBC => res_7_h,
+		0xBD => res_7_l,
+		0xBE => res_7_deref_hl,
+		0xBF => res_7_a,
+		0xC0 => set_0_b,
+		0xC1 => set_0_c,
+		0xC2 => set_0_d,
+		0xC3 => set_0_e,
+		0xC4 => set_0_h,
+		0xC5 => set_0_l,
+		0xC6 => set_0_deref_hl,
+		0xC7 => set_0_a,
+		0xC8 => set_1_b,
+		0xC9 => set_1_c,
+		0xCA => set_1_d,
+		0xCB => set_1_e,
+		0xCC => set_1_h,
+		0xCD => set_1_l,
+		0xCE => set_1_deref_hl,
+		0xCF => set_1_a,
+		0xD0 => set_2_b,
+		0xD1 => set_2_c,
+		0xD2 => set_2_d,
+		0xD3 => set_2_e,
+		0xD4 => set_2_h,
+		0xD5 => set_2_l,
+		0xD6 => set_2_deref_hl,
+		0xD7 => set_2_a,
+		0xD8 => set_3_b,
+		0xD9 => set_3_c,
+		0xDA => set_3_d,
+		0xDB => set_3_e,
+		0xDC => set_3_h,
+		0xDD => set_3_l,
+		0xDE => set_3_deref_hl,
+		0xDF => set_3_a,
+		0xE0 => set_4_b,
+		0xE1 => set_4_c,
+		0xE2 => set_4_d,
+		0xE3 => set_4_e,
+		0xE4 => set_4_h,
+		0xE5 => set_4_l,
+		0xE6 => set_4_deref_hl,
+		0xE7 => set_4_a,
+		0xE8 => set_5_b,
+		0xE9 => set_5_c,
+		0xEA => set_5_d,
+		0xEB => set_5_e,
+		0xEC => set_5_h,
+		0xED => set_5_l,
+		0xEE => set_5_deref_hl,
+		0xEF => set_5_a,
+		0xF0 => set_6_b,
+		0xF1 => set_6_c,
+		0xF2 => set_6_d,
+		0xF3 => set_6_e,
+		0xF4 => set_6_h,
+		0xF5 => set_6_l,
+		0xF6 => set_6_deref_hl,
+		0xF7 => set_6_a,
+		0xF8 => set_7_b,
+		0xF9 => set_7_c,
+		0xFA => set_7_d,
+		0xFB => set_7_e,
+		0xFC => set_7_h,
+		0xFD => set_7_l,
+		0xFE => set_7_deref_hl,
+		0xFF => set_7_a,
 		unknown => panic!(
 			"Unrecognized prefixed opcode: {:#X}\nRegisters: {:#?}",
 			unknown, state.registers
@@ -109,7 +251,7 @@ pub fn prefixed_handler(state: &mut Gameboy) -> CycleResult {
 macro_rules! define_bit_reg {
 	($op:literal, $bit:literal, $reg:ident) => {
 		paste::paste! {
-			opcode!([<bit_ $bit _ $reg>], $op, std::concat!("BIT ", std::stringify!($bit), ",", std::stringify!($reg)), false, {
+			opcode!([<bit_ $bit _ $reg>], $op, std::concat!("BIT ", std::stringify!($bit), ",", std::stringify!($reg)), true, {
 					1 => {
 						state.registers.set_zero(state.registers.$reg & (1 << $bit) == 0);
 						state.registers.set_subtract(false);
@@ -182,7 +324,7 @@ define_bit_reg!(0x7f, 7, a);
 macro_rules! define_bit_deref_hl {
 	($op:literal, $bit:literal) => {
 		paste::paste! {
-			opcode!([<bit_ $bit _deref_hl>], $op, std::concat!("BIT ", std::stringify!($bit), ",(HL)"), false, {
+			opcode!([<bit_ $bit _deref_hl>], $op, std::concat!("BIT ", std::stringify!($bit), ",(HL)"), true, {
 				1 => {
 					state.cpu_read_u8(state.registers.get_hl());
 					CycleResult::NeedsMore
@@ -212,7 +354,7 @@ define_bit_deref_hl!(0x7e, 7);
 macro_rules! define_rl_reg {
 	($op:literal, $reg:ident) => {
 		paste::paste! {
-			opcode!([<rl_ $reg>], $op, std::concat!("RL ", std::stringify!($reg)), false, {
+			opcode!([<rl_ $reg>], $op, std::concat!("RL ", std::stringify!($reg)), true, {
 					1 => {
 						let carry = state.registers.$reg >> 7 == 1;
 						state.registers.$reg <<= 1;
@@ -244,7 +386,7 @@ define_rl_reg!(0x17, a);
 macro_rules! define_swap_reg {
 	($op:literal, $reg:ident) => {
 		paste::paste! {
-			opcode!([<swap_ $reg>], $op, std::concat!("SWAP ", std::stringify!($reg)), false, {
+			opcode!([<swap_ $reg>], $op, std::concat!("SWAP ", std::stringify!($reg)), true, {
 				1 => {
 					state.registers.$reg = (state.registers.$reg >> 4) | (state.registers.$reg << 4);
 
@@ -267,3 +409,263 @@ define_swap_reg!(0x33, e);
 define_swap_reg!(0x34, h);
 define_swap_reg!(0x35, l);
 define_swap_reg!(0x37, a);
+
+macro_rules! define_srl_reg {
+	($op:literal, $reg:ident) => {
+		paste::paste! {
+			opcode!([<srl_ $reg>], $op, std::concat!("SRL ", std::stringify!($reg)), true, {
+				1 => {
+					let carry = state.registers.$reg & 0b1 == 1;
+					state.registers.$reg >>= 1;
+
+					state.registers.set_zero(state.registers.$reg == 0);
+					state.registers.set_subtract(false);
+					state.registers.set_half_carry(false);
+					state.registers.set_carry(carry);
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_srl_reg!(0x38, b);
+define_srl_reg!(0x39, c);
+define_srl_reg!(0x3a, d);
+define_srl_reg!(0x3b, e);
+define_srl_reg!(0x3c, h);
+define_srl_reg!(0x3d, l);
+define_srl_reg!(0x3f, a);
+
+macro_rules! define_rr_reg {
+	($op:literal, $reg:ident) => {
+		paste::paste! {
+			opcode!([<rr_ $reg>], $op, std::concat!("RR ", std::stringify!($reg)), true, {
+				1 => {
+					let carry = state.registers.$reg & 0b1 == 1;
+					state.registers.$reg >>= 1;
+
+					state.registers.set_zero(state.registers.$reg == 0);
+					state.registers.set_subtract(false);
+					state.registers.set_half_carry(false);
+					state.registers.set_carry(carry);
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_rr_reg!(0x18, b);
+define_rr_reg!(0x19, c);
+define_rr_reg!(0x1a, d);
+define_rr_reg!(0x1b, e);
+define_rr_reg!(0x1c, h);
+define_rr_reg!(0x1d, l);
+define_rr_reg!(0x1f, a);
+
+macro_rules! define_res_idx_reg {
+	($op:literal, $idx:literal, $reg:ident) => {
+		paste::paste! {
+			opcode!([<res_ $idx _ $reg>], $op, std::concat!("RES ", std::stringify!($idx), ", ", std::stringify!($reg)), true, {
+				1 => {
+					state.registers.$reg &= !(1u8 << $idx);
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_res_idx_reg!(0x80, 0, b);
+define_res_idx_reg!(0x81, 0, c);
+define_res_idx_reg!(0x82, 0, d);
+define_res_idx_reg!(0x83, 0, e);
+define_res_idx_reg!(0x84, 0, h);
+define_res_idx_reg!(0x85, 0, l);
+define_res_idx_reg!(0x87, 0, a);
+define_res_idx_reg!(0x88, 1, b);
+define_res_idx_reg!(0x89, 1, c);
+define_res_idx_reg!(0x8a, 1, d);
+define_res_idx_reg!(0x8b, 1, e);
+define_res_idx_reg!(0x8c, 1, h);
+define_res_idx_reg!(0x8d, 1, l);
+define_res_idx_reg!(0x8f, 1, a);
+define_res_idx_reg!(0x90, 2, b);
+define_res_idx_reg!(0x91, 2, c);
+define_res_idx_reg!(0x92, 2, d);
+define_res_idx_reg!(0x93, 2, e);
+define_res_idx_reg!(0x94, 2, h);
+define_res_idx_reg!(0x95, 2, l);
+define_res_idx_reg!(0x97, 2, a);
+define_res_idx_reg!(0x98, 3, b);
+define_res_idx_reg!(0x99, 3, c);
+define_res_idx_reg!(0x9a, 3, d);
+define_res_idx_reg!(0x9b, 3, e);
+define_res_idx_reg!(0x9c, 3, h);
+define_res_idx_reg!(0x9d, 3, l);
+define_res_idx_reg!(0x9f, 3, a);
+define_res_idx_reg!(0xa0, 4, b);
+define_res_idx_reg!(0xa1, 4, c);
+define_res_idx_reg!(0xa2, 4, d);
+define_res_idx_reg!(0xa3, 4, e);
+define_res_idx_reg!(0xa4, 4, h);
+define_res_idx_reg!(0xa5, 4, l);
+define_res_idx_reg!(0xa7, 4, a);
+define_res_idx_reg!(0xa8, 5, b);
+define_res_idx_reg!(0xa9, 5, c);
+define_res_idx_reg!(0xaa, 5, d);
+define_res_idx_reg!(0xab, 5, e);
+define_res_idx_reg!(0xac, 5, h);
+define_res_idx_reg!(0xad, 5, l);
+define_res_idx_reg!(0xaf, 5, a);
+define_res_idx_reg!(0xb0, 6, b);
+define_res_idx_reg!(0xb1, 6, c);
+define_res_idx_reg!(0xb2, 6, d);
+define_res_idx_reg!(0xb3, 6, e);
+define_res_idx_reg!(0xb4, 6, h);
+define_res_idx_reg!(0xb5, 6, l);
+define_res_idx_reg!(0xb7, 6, a);
+define_res_idx_reg!(0xb8, 7, b);
+define_res_idx_reg!(0xb9, 7, c);
+define_res_idx_reg!(0xba, 7, d);
+define_res_idx_reg!(0xbb, 7, e);
+define_res_idx_reg!(0xbc, 7, h);
+define_res_idx_reg!(0xbd, 7, l);
+define_res_idx_reg!(0xbf, 7, a);
+
+macro_rules! define_res_idx_deref_hl {
+	($op:literal, $idx:literal) => {
+		paste::paste! {
+			opcode!([<res_ $idx _deref_hl>], $op, std::concat!("RES ", std::stringify!($idx), ", (HL)"), true, {
+				1 => {
+					state.cpu_read_u8(state.registers.get_hl());
+					CycleResult::NeedsMore
+				},
+				2 => {
+					let res = state.registers.take_mem() & !(1u8 << $idx);
+					state.cpu_write_u8(state.registers.get_hl(), res);
+					CycleResult::NeedsMore
+				},
+				3 => {
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_res_idx_deref_hl!(0x86, 0);
+define_res_idx_deref_hl!(0x8E, 1);
+define_res_idx_deref_hl!(0x96, 2);
+define_res_idx_deref_hl!(0x9E, 3);
+define_res_idx_deref_hl!(0xA6, 4);
+define_res_idx_deref_hl!(0xAE, 5);
+define_res_idx_deref_hl!(0xB6, 6);
+define_res_idx_deref_hl!(0xBE, 7);
+
+macro_rules! define_set_idx_reg {
+	($op:literal, $idx:literal, $reg:ident) => {
+		paste::paste! {
+			opcode!([<set_ $idx _ $reg>], $op, std::concat!("SET ", std::stringify!($idx), ", ", std::stringify!($reg)), true, {
+				1 => {
+					state.registers.$reg |= 1u8 << $idx;
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_set_idx_reg!(0xc0, 0, b);
+define_set_idx_reg!(0xc1, 0, c);
+define_set_idx_reg!(0xc2, 0, d);
+define_set_idx_reg!(0xc3, 0, e);
+define_set_idx_reg!(0xc4, 0, h);
+define_set_idx_reg!(0xc5, 0, l);
+define_set_idx_reg!(0xc7, 0, a);
+define_set_idx_reg!(0xc8, 1, b);
+define_set_idx_reg!(0xc9, 1, c);
+define_set_idx_reg!(0xca, 1, d);
+define_set_idx_reg!(0xcb, 1, e);
+define_set_idx_reg!(0xcc, 1, h);
+define_set_idx_reg!(0xcd, 1, l);
+define_set_idx_reg!(0xcf, 1, a);
+define_set_idx_reg!(0xd0, 2, b);
+define_set_idx_reg!(0xd1, 2, c);
+define_set_idx_reg!(0xd2, 2, d);
+define_set_idx_reg!(0xd3, 2, e);
+define_set_idx_reg!(0xd4, 2, h);
+define_set_idx_reg!(0xd5, 2, l);
+define_set_idx_reg!(0xd7, 2, a);
+define_set_idx_reg!(0xd8, 3, b);
+define_set_idx_reg!(0xd9, 3, c);
+define_set_idx_reg!(0xda, 3, d);
+define_set_idx_reg!(0xdb, 3, e);
+define_set_idx_reg!(0xdc, 3, h);
+define_set_idx_reg!(0xdd, 3, l);
+define_set_idx_reg!(0xdf, 3, a);
+define_set_idx_reg!(0xe0, 4, b);
+define_set_idx_reg!(0xe1, 4, c);
+define_set_idx_reg!(0xe2, 4, d);
+define_set_idx_reg!(0xe3, 4, e);
+define_set_idx_reg!(0xe4, 4, h);
+define_set_idx_reg!(0xe5, 4, l);
+define_set_idx_reg!(0xe7, 4, a);
+define_set_idx_reg!(0xe8, 5, b);
+define_set_idx_reg!(0xe9, 5, c);
+define_set_idx_reg!(0xea, 5, d);
+define_set_idx_reg!(0xeb, 5, e);
+define_set_idx_reg!(0xec, 5, h);
+define_set_idx_reg!(0xed, 5, l);
+define_set_idx_reg!(0xef, 5, a);
+define_set_idx_reg!(0xf0, 6, b);
+define_set_idx_reg!(0xf1, 6, c);
+define_set_idx_reg!(0xf2, 6, d);
+define_set_idx_reg!(0xf3, 6, e);
+define_set_idx_reg!(0xf4, 6, h);
+define_set_idx_reg!(0xf5, 6, l);
+define_set_idx_reg!(0xf7, 6, a);
+define_set_idx_reg!(0xf8, 7, b);
+define_set_idx_reg!(0xf9, 7, c);
+define_set_idx_reg!(0xfa, 7, d);
+define_set_idx_reg!(0xfb, 7, e);
+define_set_idx_reg!(0xfc, 7, h);
+define_set_idx_reg!(0xfd, 7, l);
+define_set_idx_reg!(0xff, 7, a);
+
+macro_rules! define_set_idx_deref_hl {
+	($op:literal, $idx:literal) => {
+		paste::paste! {
+			opcode!([<set_ $idx _deref_hl>], $op, std::concat!("SET ", std::stringify!($idx), ", (HL)"), true, {
+				1 => {
+					state.cpu_read_u8(state.registers.get_hl());
+					CycleResult::NeedsMore
+				},
+				2 => {
+					let res = state.registers.take_mem() | (1u8 << $idx);
+					state.cpu_write_u8(state.registers.get_hl(), res);
+					CycleResult::NeedsMore
+				},
+				3 => {
+					state.registers.opcode_bytecount = Some(2);
+					CycleResult::Finished
+				}
+			});
+		}
+	};
+}
+
+define_set_idx_deref_hl!(0xC6, 0);
+define_set_idx_deref_hl!(0xCE, 1);
+define_set_idx_deref_hl!(0xD6, 2);
+define_set_idx_deref_hl!(0xDE, 3);
+define_set_idx_deref_hl!(0xE6, 4);
+define_set_idx_deref_hl!(0xEE, 5);
+define_set_idx_deref_hl!(0xF6, 6);
+define_set_idx_deref_hl!(0xFE, 7);
diff --git a/deemgee/src/gameboy/interrupts.rs b/deemgee/src/gameboy/interrupts.rs
index f08742b..0a43f61 100644
--- a/deemgee/src/gameboy/interrupts.rs
+++ b/deemgee/src/gameboy/interrupts.rs
@@ -16,13 +16,14 @@ macro_rules! define_bitfield_u8_gs {
 
 pub struct Interrupts {
 	pub ime: bool,
+	pub ei_queued: bool,
 	pub interrupt_enable: u8,
 	pub interrupt_flag: u8,
 }
 
 impl Interrupts {
 	pub fn new() -> Self {
-		Self { ime: false, interrupt_enable: 0, interrupt_flag: 0 }
+		Self { ime: false, interrupt_enable: 0, interrupt_flag: 0, ei_queued: false }
 	}
 
 	define_bitfield_u8_gs!(ie_vblank, 0, interrupt_enable);
@@ -35,4 +36,11 @@ impl Interrupts {
 	define_bitfield_u8_gs!(if_timer, 2, interrupt_flag);
 	define_bitfield_u8_gs!(if_serial, 3, interrupt_flag);
 	define_bitfield_u8_gs!(if_joypad, 4, interrupt_flag);
+
+	pub fn cpu_set_ime(&mut self, val: bool) {
+		self.ei_queued = val;
+		if !val {
+			self.ime = false;
+		}
+	}
 }
diff --git a/deemgee/src/gameboy/joypad.rs b/deemgee/src/gameboy/joypad.rs
index e55d4ce..7347bef 100644
--- a/deemgee/src/gameboy/joypad.rs
+++ b/deemgee/src/gameboy/joypad.rs
@@ -4,6 +4,19 @@ pub enum JoypadMode {
 	Direction,
 }
 
+macro_rules! joypad_input {
+	($input:ident, $mode:ident) => {
+		paste::paste! {
+			pub fn [<set_ $input>](&mut self, val: bool) {
+				if val && self.mode == JoypadMode::$mode {
+					self.interrupt_triggered = true;
+				}
+				self.$input = val
+			}
+		}
+	};
+}
+
 pub struct Joypad {
 	mode: JoypadMode,
 	pub down: bool,
@@ -14,6 +27,7 @@ pub struct Joypad {
 	pub select: bool,
 	pub b: bool,
 	pub a: bool,
+	pub interrupt_triggered: bool,
 }
 
 impl Joypad {
@@ -28,6 +42,7 @@ impl Joypad {
 			select: false,
 			b: false,
 			a: false,
+			interrupt_triggered: false,
 		}
 	}
 
@@ -50,6 +65,15 @@ impl Joypad {
 		}
 	}
 
+	joypad_input!(a, Action);
+	joypad_input!(b, Action);
+	joypad_input!(start, Action);
+	joypad_input!(select, Action);
+	joypad_input!(up, Direction);
+	joypad_input!(down, Direction);
+	joypad_input!(left, Direction);
+	joypad_input!(right, Direction);
+
 	pub fn cpu_write(&mut self, content: u8) {
 		if (content >> 5) & 0b1 == 0 {
 			self.mode = JoypadMode::Action;
diff --git a/deemgee/src/gameboy/mapper.rs b/deemgee/src/gameboy/mapper.rs
index 9061e5c..8c09e6c 100644
--- a/deemgee/src/gameboy/mapper.rs
+++ b/deemgee/src/gameboy/mapper.rs
@@ -1,3 +1,5 @@
+pub mod mbc1;
+
 pub trait Mapper {
 	fn read_rom_u8(&self, address: u16) -> u8;
 	fn write_rom_u8(&mut self, address: u16, value: u8);
diff --git a/deemgee/src/gameboy/mapper/mbc1.rs b/deemgee/src/gameboy/mapper/mbc1.rs
new file mode 100644
index 0000000..4e378cb
--- /dev/null
+++ b/deemgee/src/gameboy/mapper/mbc1.rs
@@ -0,0 +1,114 @@
+use super::Mapper;
+
+pub struct MBC1 {
+	rom: Vec<u8>,
+	ram: Option<Vec<u8>>,
+	rom_bank_count: u8,
+	ram_bank_count: u8,
+	ram_enabled: bool,
+	rom_bank_number: u8,
+	extra_2_bit_reg: u8,
+	banking_mode_select: bool,
+}
+
+impl MBC1 {
+	pub fn new(data: Vec<u8>) -> Self {
+		let rom_bank_count = 0b10 << data[0x148];
+		let ram_bank_count = match data[0x149] {
+			0 | 1 => 0,
+			2 => 1,
+			3 => 4,
+			4 => 16,
+			5 => 8,
+			_ => panic!("Bad RAM bank count for MBC1"),
+		};
+
+		let ram = match ram_bank_count {
+			0 | 1 => None,
+			2 | 3 | 4 | 5 => Some(vec![0u8; ram_bank_count as usize * (8 * 1024)]),
+			_ => panic!("Bad RAM bank count for MBC1"),
+		};
+
+		assert_eq!(data.len(), rom_bank_count as usize * (16 * 1024));
+
+		Self {
+			rom: data,
+			rom_bank_count,
+			ram_enabled: false,
+			rom_bank_number: 1,
+			extra_2_bit_reg: 0,
+			ram,
+			ram_bank_count,
+			banking_mode_select: false,
+		}
+	}
+
+	fn set_ram_enabled(&mut self, val: u8) {
+		self.ram_enabled = val & 0xA != 0;
+	}
+
+	fn set_rom_bank_number(&mut self, mut val: u8) {
+		if val == 0 {
+			val = 1;
+		}
+		self.rom_bank_number = val & 0b1_1111;
+	}
+
+	fn set_extra_2_bit_reg(&mut self, val: u8) {
+		self.extra_2_bit_reg = val & 0b11;
+	}
+
+	fn set_banking_mode_select(&mut self, val: u8) {
+		self.banking_mode_select = val & 0b1 == 1;
+	}
+
+	fn is_large_rom(&self) -> bool {
+		self.rom_bank_count > 4
+	}
+
+	fn is_large_ram(&self) -> bool {
+		self.ram_bank_count > 2
+	}
+}
+
+impl Mapper for MBC1 {
+	fn read_rom_u8(&self, address: u16) -> u8 {
+		if address <= 0x3FFF {
+			self.rom[if self.is_large_rom() && self.banking_mode_select {
+				((self.extra_2_bit_reg << 5) as usize * 0x4000) + address as usize
+			} else {
+				address as usize
+			}]
+		} else {
+			self.rom[if self.is_large_rom() {
+				(self.rom_bank_number | (self.extra_2_bit_reg << 5)) as usize * 0x4000
+			} else {
+				self.rom_bank_number as usize * 0x4000
+			}]
+		}
+	}
+
+	fn write_rom_u8(&mut self, address: u16, value: u8) {
+		match address {
+			0..=0x1FFF => self.set_ram_enabled(value),
+			0x2000..=0x3FFF => self.set_rom_bank_number(value),
+			0x4000..=0x5FFF => self.set_extra_2_bit_reg(value),
+			0x6000..=0x7FFF => self.set_banking_mode_select(value),
+			_ => unreachable!(),
+		}
+	}
+
+	fn read_eram_u8(&self, address: u16) -> u8 {
+		match self.ram.as_ref() {
+			Some(ram) => unimplemented!(),
+			None => 0,
+		}
+	}
+
+	fn write_eram_u8(&mut self, address: u16, value: u8) {
+		match self.ram.as_ref() {
+			Some(ram) => unimplemented!(),
+			None => {}
+		}
+	}
+}
diff --git a/deemgee/src/gameboy/ppu.rs b/deemgee/src/gameboy/ppu.rs
index 14e1855..ccf7784 100644
--- a/deemgee/src/gameboy/ppu.rs
+++ b/deemgee/src/gameboy/ppu.rs
@@ -317,18 +317,18 @@ impl Ppu {
 				}
 
 				if entry.y_flip() {
-					tile_y_idx = 8 - tile_y_idx;
+					tile_y_idx = 7 - tile_y_idx;
 				}
 
 				let tile_idx =
 					if is_second_tile { entry.tile_idx | 1 } else { entry.tile_idx & 0xFE };
 
 				for x in 0..8 {
-					let fb_x = entry.x.overflowing_sub(8 - x).0;
+					let fb_x = entry.x.overflowing_sub(7 - x).0;
 
 					let sprite_line_base = fb_x as usize * 4;
 
-					let tile_x_idx = if entry.x_flip() { 8 - x } else { x };
+					let tile_x_idx = if entry.x_flip() { 7 - x } else { x };
 
 					let color = Self::parse_sprite_tile_color(
 						self.read_obj_tile(tile_idx),
@@ -386,7 +386,7 @@ impl Ppu {
 	}
 
 	fn set_mode(&mut self, interrupts: &mut Interrupts, mode: PPUMode) {
-		log::debug!("PPU switching mode to {:?} @ {}", mode, self.cycle_counter);
+		log::trace!("PPU switching mode to {:?} @ {}", mode, self.cycle_counter);
 		self.stat &= !0b11;
 		self.stat |= mode.mode_flag();
 		self.cycle_counter = 0;
diff --git a/deemgee/src/gameboy/serial.rs b/deemgee/src/gameboy/serial.rs
index 7c9dfe5..c06612d 100644
--- a/deemgee/src/gameboy/serial.rs
+++ b/deemgee/src/gameboy/serial.rs
@@ -1,11 +1,15 @@
+use std::io::Write;
+
 pub struct Serial {
 	pub sb: u8,
 	pub sc: u8,
+
+	internal_tick: u16,
 }
 
 impl Serial {
 	pub fn new() -> Serial {
-		Self { sb: 0, sc: 0 }
+		Self { sb: 0, sc: 0, internal_tick: 0 }
 	}
 
 	pub fn set_transfer_in_process(&mut self, value: bool) {
@@ -25,4 +29,20 @@ impl Serial {
 		self.sc &= !0b1;
 		self.sc |= conductor as u8;
 	}
+
+	pub fn tick(&mut self) -> bool {
+		if self.get_transfer_in_process() && self.is_conductor() {
+			if self.internal_tick < 128 {
+				self.internal_tick += 1;
+			} else {
+				print!("{}", self.sb as char);
+				std::io::stdout().flush().expect("flushing stdout failed");
+				self.sb = 0;
+				self.set_transfer_in_process(false);
+				self.internal_tick = 0;
+				return true;
+			}
+		}
+		false
+	}
 }
diff --git a/deemgee/src/gameboy/timer.rs b/deemgee/src/gameboy/timer.rs
index 3310ce8..4f299f5 100644
--- a/deemgee/src/gameboy/timer.rs
+++ b/deemgee/src/gameboy/timer.rs
@@ -30,7 +30,7 @@ impl Timer {
 		if self.enable {
 			self.tima_counter = self.tima_counter.overflowing_add(1).0;
 			if self.tima_counter >= self.clock.cycles() {
-				self.tima += self.tima.overflowing_add(1).0;
+				self.tima = self.tima.overflowing_add(1).0;
 
 				return self.tima == 0;
 			}
@@ -80,7 +80,7 @@ impl TimerClock {
 			1 => Self::C16,
 			2 => Self::C64,
 			3 => Self::C256,
-			4 => Self::C1024,
+			0 => Self::C1024,
 			_ => unreachable!(),
 		}
 	}
diff --git a/deemgee/src/main.rs b/deemgee/src/main.rs
index d05e752..bfdcb64 100644
--- a/deemgee/src/main.rs
+++ b/deemgee/src/main.rs
@@ -103,14 +103,16 @@ pub fn run_gameboy(
 	'outer: loop {
 		while let Ok(event) = rx.try_recv() {
 			match event {
-				window::WindowEvent::AToggle => gameboy.joypad.a = !gameboy.joypad.a,
-				window::WindowEvent::BToggle => gameboy.joypad.b = !gameboy.joypad.b,
-				window::WindowEvent::SelectToggle => gameboy.joypad.select = !gameboy.joypad.select,
-				window::WindowEvent::StartToggle => gameboy.joypad.start = !gameboy.joypad.start,
-				window::WindowEvent::UpToggle => gameboy.joypad.up = !gameboy.joypad.up,
-				window::WindowEvent::DownToggle => gameboy.joypad.down = !gameboy.joypad.down,
-				window::WindowEvent::LeftToggle => gameboy.joypad.left = !gameboy.joypad.left,
-				window::WindowEvent::RightToggle => gameboy.joypad.right = !gameboy.joypad.right,
+				window::WindowEvent::AToggle => gameboy.joypad.set_a(!gameboy.joypad.a),
+				window::WindowEvent::BToggle => gameboy.joypad.set_b(!gameboy.joypad.b),
+				window::WindowEvent::SelectToggle => {
+					gameboy.joypad.set_select(!gameboy.joypad.select)
+				}
+				window::WindowEvent::StartToggle => gameboy.joypad.set_start(!gameboy.joypad.start),
+				window::WindowEvent::UpToggle => gameboy.joypad.set_up(!gameboy.joypad.up),
+				window::WindowEvent::DownToggle => gameboy.joypad.set_down(!gameboy.joypad.down),
+				window::WindowEvent::LeftToggle => gameboy.joypad.set_left(!gameboy.joypad.left),
+				window::WindowEvent::RightToggle => gameboy.joypad.set_right(!gameboy.joypad.right),
 				window::WindowEvent::PauseToggle => paused = !paused,
 				window::WindowEvent::LogToggle => {
 					gameboy.log_instructions = !gameboy.log_instructions