diff --git a/core/src/cpu/disassembler.rs b/core/src/cpu/disassembler.rs
index 7ffd516..ede8a22 100644
--- a/core/src/cpu/disassembler.rs
+++ b/core/src/cpu/disassembler.rs
@@ -2,14 +2,14 @@ use crate::cpu::op::AddressingMode::*;
 use crate::cpu::op::{AddressingMode, Instruction};
 use crate::cpu::Cpu;
 
-impl Cpu<'_> {
+impl Cpu {
     pub fn disassemble_next_instr(&self) {
         let registers = self.registers;
-        let op_code = self.memory_bus.get_byte(registers.pc);
+        let op_code = self.memory_bus.borrow().get_byte(registers.pc) as usize;
 
         let instr: Instruction = Self::INSTRUCTIONS[op_code];
         let operation = instr.op().to_string();
-        let addr_mode = self.disassemble_addr_mode(instr.addr_mode());
+        let addr_mode = self.disassemble_addr_mode(instr.addr_mode(), registers.pc);
 
         dbg!(
             "DIS {:#04x} - {:#02x} {:?} {:?} - A {:#02x}, X {:#02x}, Y {:#02x}, SP: {:#02x}, F: {:#02x}",
@@ -26,7 +26,7 @@ impl Cpu<'_> {
     }
 
     fn disassemble_addr_mode(&self, addr_mode: AddressingMode, pc: u16) -> String {
-        let word_peek = self.memory_bus.get_word(pc);
+        let word_peek = self.memory_bus.borrow().get_word(pc);
         let byte_peek = (word_peek & 0xFF) as u8;
 
         match addr_mode {
diff --git a/core/src/cpu/mod.rs b/core/src/cpu/mod.rs
index cf7f2a1..31bb372 100644
--- a/core/src/cpu/mod.rs
+++ b/core/src/cpu/mod.rs
@@ -2,6 +2,7 @@ mod disassembler;
 mod op;
 mod operations;
 
+use std::cell::RefCell;
 use crate::memory::MemoryBus;
 use crate::Clock;
 use bitflags::bitflags;
@@ -9,18 +10,18 @@ use bitflags::bitflags;
 const STACK_ADDR: u16 = 0x0100;
 
 /// Represents a 6502 CPU
-struct Cpu<'a> {
+pub struct Cpu {
     /// The registers of the CPU
     registers: CpuRegisters,
 
     /// The memory bus accessible by the CPU
-    memory_bus: &'a MemoryBus,
+    memory_bus: RefCell<MemoryBus>,
 
     /// The number of cycles ran on the CPU
-    cycle: u32,
+    cycle: usize,
 
     /// The amount of cycles the CPU will be busy for (won't execute any instruction)
-    busy_cycle_count: u16,
+    busy_cycle_count: usize,
 
     /// Whether an OAM DMA was triggered (data transfer to the PPU OAM memory)
     oam_dma_triggered: bool,
@@ -131,8 +132,8 @@ pub trait CpuInternals {
     fn stack_pop_context(&mut self);
 }
 
-impl<'a> Cpu<'a> {
-    pub fn new(memory_bus: &mut MemoryBus) -> Self {
+impl Cpu {
+    pub fn new(memory_bus: RefCell<MemoryBus>) -> Self {
         Cpu {
             registers: CpuRegisters {
                 pc: 0x8000,
@@ -151,9 +152,9 @@ impl<'a> Cpu<'a> {
     }
 }
 
-impl CpuInternals for Cpu<'_> {
+impl CpuInternals for Cpu {
     fn get_status_flag(&self, flag: CpuStatus) -> bool {
-        *self.registers.status & flag
+        self.registers.status & flag.bits() > 0
     }
 
     fn get_status_flag_u8(&self, flag: CpuStatus) -> u8 {
@@ -166,14 +167,14 @@ impl CpuInternals for Cpu<'_> {
     }
 
     fn program_get_next_byte(&mut self) -> u8 {
-        let byte = self.memory_bus.get_byte(self.registers.pc);
+        let byte = self.memory_bus.borrow().get_byte(self.registers.pc);
         self.registers.pc += 1;
 
         byte
     }
 
     fn program_get_next_word(&mut self) -> u16 {
-        let word = self.memory_bus.get_word(self.registers.pc);
+        let word = self.memory_bus.borrow().get_word(self.registers.pc);
         self.registers.pc += 2;
 
         word
@@ -181,9 +182,9 @@ impl CpuInternals for Cpu<'_> {
 
     fn set_status_flag(&mut self, flag: CpuStatus, set: bool) {
         if set {
-            *self.registers.status |= flag;
+            self.registers.status |= flag.bits();
         } else {
-            *self.registers.status &= !flag;
+            self.registers.status &= !flag.bits();
         }
     }
 
@@ -196,7 +197,7 @@ impl CpuInternals for Cpu<'_> {
         assert!(self.registers.sp > 0);
 
         let addr = STACK_ADDR | self.registers.sp as u16;
-        self.memory_bus.set_byte(addr, value);
+        self.memory_bus.borrow_mut().set_byte(addr, value);
         self.registers.sp -= 1;
     }
 
@@ -211,7 +212,7 @@ impl CpuInternals for Cpu<'_> {
         self.registers.sp += 1;
         let addr = STACK_ADDR | self.registers.sp as u16;
 
-        self.memory_bus.get_byte(addr)
+        self.memory_bus.borrow().get_byte(addr)
     }
 
     fn stack_pop_word(&mut self) -> u16 {
@@ -240,7 +241,7 @@ impl CpuInternals for Cpu<'_> {
     }
 }
 
-impl Clock for Cpu<'_> {
+impl Clock for Cpu {
     fn cycle(&mut self) {
         self.cycle += 1;
 
@@ -252,7 +253,7 @@ impl Clock for Cpu<'_> {
         self.disassemble_next_instr();
 
         let op_code = self.program_get_next_byte();
-        let instr = Self::INSTRUCTIONS[op_code];
+        let instr = Self::INSTRUCTIONS[op_code as usize];
 
         self.busy_cycle_count = instr.cycles();
         self.exec_instruction(instr);
diff --git a/core/src/cpu/op.rs b/core/src/cpu/op.rs
index f0a5ff0..5c6d0a9 100644
--- a/core/src/cpu/op.rs
+++ b/core/src/cpu/op.rs
@@ -31,13 +31,10 @@ use OperationType::{
 };
 
 /// CPU Instruction.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Instruction(u8, AddressingMode, OperationType, usize);
 
 impl Instruction {
-    pub const fn opcode(&self) -> u8 {
-        self.0
-    }
-
     pub const fn addr_mode(&self) -> AddressingMode {
         self.1
     }
@@ -69,7 +66,7 @@ impl Operand {
         self.value as u8
     }
 
-    pub const fn is_address(&self) -> bool {
+    pub fn is_address(&self) -> bool {
         self.operand_type == OperandType::Address
     }
 
@@ -79,7 +76,7 @@ impl Operand {
             OperandType::Immediate => self.value_u8(),
             OperandType::Address => {
                 let addr = self.value;
-                cpu.memory_bus.get_byte(addr)
+                cpu.memory_bus.borrow().get_byte(addr)
             }
         }
     }
@@ -89,7 +86,7 @@ impl Operand {
             OperandType::Accumulator => cpu.registers.a = value,
             OperandType::Address => {
                 let addr = self.value;
-                cpu.memory_bus.set_byte(addr, value);
+                cpu.memory_bus.borrow_mut().set_byte(addr, value);
             }
             OperandType::Immediate => unreachable!("Cannot write to immediate operand"),
         }
@@ -97,7 +94,7 @@ impl Operand {
 }
 
 // Operands
-impl Cpu<'_> {
+impl Cpu {
     /// 16x16 grid of 6502 opcodes. Matches datasheet matrix for easy lookup
     #[rustfmt::skip]
     pub const INSTRUCTIONS: [Instruction; 256] = [
@@ -119,13 +116,6 @@ impl Cpu<'_> {
         Instruction(0xF0, REL, BEQ, 2), Instruction(0xF1, IDY, SBC, 5), Instruction(0xF2, IMP, STP, 2), Instruction(0xF3, IDY, ISB, 8), Instruction(0xF4, ZPX, NOP, 4), Instruction(0xF5, ZPX, SBC, 4), Instruction(0xF6, ZPX, INC, 6), Instruction(0xF7, ZPX, ISB, 6), Instruction(0xF8, IMP, SED, 2), Instruction(0xF9, ABY, SBC, 4), Instruction(0xFA, IMP, NOP, 2), Instruction(0xFB, ABY, ISB, 7), Instruction(0xFC, ABX, NOP, 4), Instruction(0xFD, ABX, SBC, 4), Instruction(0xFE, ABX, INC, 7), Instruction(0xFF, ABX, ISB, 7),
     ];
 
-    pub fn read_next_instruction(&mut self) -> Instruction {
-        let op_code = self.program_get_next_byte();
-        let instruction = Instruction[op_code];
-
-        instruction
-    }
-
     /// Decodes the next operand in memory
     ///
     /// # Arguments
@@ -226,11 +216,11 @@ impl Cpu<'_> {
 
         if ref_addr & 0xFF == 0xFF {
             // Error in NES CPU for JMP op
-            let low = self.memory_bus.get_byte(ref_addr) as u16;
-            let high = self.memory_bus.get_byte(ref_addr & 0xFF00) as u16;
+            let low = self.memory_bus.borrow().get_byte(ref_addr) as u16;
+            let high = self.memory_bus.borrow().get_byte(ref_addr & 0xFF00) as u16;
             low + (high << 8)
         } else {
-            self.memory_bus.get_word(ref_addr)
+            self.memory_bus.borrow().get_word(ref_addr)
         }
     }
 
@@ -239,17 +229,17 @@ impl Cpu<'_> {
         let mut ref_addr = self.program_get_next_byte() as u16;
         ref_addr += self.registers.x as u16;
 
-        let low = self.memory_bus.get_byte(ref_addr & 0xFF) as u16;
-        let high = self.memory_bus.get_byte((ref_addr + 1) & 0xFF) as u16;
+        let low = self.memory_bus.borrow().get_byte(ref_addr & 0xFF) as u16;
+        let high = self.memory_bus.borrow().get_byte((ref_addr + 1) & 0xFF) as u16;
         low + (high << 8)
     }
 
     /// (d),y - PEEK(byte) + Y
     fn operand_addr_indy(&mut self, page_crossed: &mut bool) -> u16 {
-        let mut ref_addr = self.program_get_next_byte() as u16;
+        let ref_addr = self.program_get_next_byte() as u16;
 
-        let low = self.memory_bus.get_byte(ref_addr) as u16;
-        let high = self.memory_bus.get_byte((ref_addr + 1) & 0xFF) as u16;
+        let low = self.memory_bus.borrow().get_byte(ref_addr) as u16;
+        let high = self.memory_bus.borrow().get_byte((ref_addr + 1) & 0xFF) as u16;
         let addr = low + (high << 8);
         let incr_addr = addr + self.registers.y as u16;
 
@@ -265,7 +255,7 @@ impl Cpu<'_> {
 
         // The offset is signed
         let positive_offset = offset & 0x7F;
-        if offset & 0x80 {
+        if offset & 0x80 > 0 {
             base_addr.wrapping_sub(positive_offset)
         } else {
             base_addr.wrapping_add(positive_offset)
diff --git a/core/src/cpu/operations.rs b/core/src/cpu/operations.rs
index 5501d28..477e875 100644
--- a/core/src/cpu/operations.rs
+++ b/core/src/cpu/operations.rs
@@ -7,7 +7,7 @@ fn is_sign_overflow(val1: u8, val2: u8, result: u8) -> bool {
     (val1 & 0x80 == val2 & 0x80) && (val1 & 0x80 != result & 0x80)
 }
 
-impl Cpu<'_> {
+impl Cpu {
     pub fn exec_instruction(&mut self, instr: Instruction) {
         let operand = self.operand_decode(instr.addr_mode());
         if operand.is_page_crossing {
@@ -322,6 +322,11 @@ impl Cpu<'_> {
         self.set_status_flag(CpuStatus::Carry, false);
     }
 
+    /// Clear decimal flag
+    fn op_cld(&mut self, operand: Operand) {
+        self.set_status_flag(CpuStatus::Decimal, false);
+    }
+
     /// Clear interrupt disable flag
     fn op_cli(&mut self, operand: Operand) {
         self.set_status_flag(CpuStatus::InterruptDisable, false);
@@ -470,7 +475,7 @@ impl Cpu<'_> {
             value
         } else {
             assert_eq!(addr_mode, AddressingMode::IND);
-            self.memory_bus.get_word(value)
+            self.memory_bus.borrow().get_word(value)
         };
 
         self.registers.pc = target_addr;
@@ -840,6 +845,13 @@ impl Cpu<'_> {
         self.set_common_flags(x);
     }
 
+    /// Transfer X to stack pointer
+    fn op_txs(&mut self, operand: Operand) {
+        let x = self.registers.x;
+
+        self.registers.sp = x;
+    }
+
     /// Transfer Y to A
     fn op_tya(&mut self, operand: Operand) {
         let y = self.registers.y;
diff --git a/core/src/rom/mod.rs b/core/src/rom/mod.rs
index ac6d57f..ecfda45 100644
--- a/core/src/rom/mod.rs
+++ b/core/src/rom/mod.rs
@@ -99,7 +99,7 @@ impl Rom {
     }
 }
 
-enum RomReadError {
+pub enum RomReadError {
     FormatNotSupported,
     Io(std::io::Error),
     InvalidHeader(String),