Set initial PC from ROM

core/Cargo.toml

@@ -8,4 +8,4 @@ edition = "2021"
 [dependencies]
 bitflags = "2.7.0"
 simplelog = { version = "^0.12.0", features = ["paris"] }
-strum = { version = "0.26", features = ["derive"] }
+strum = { version = "0.26", features = ["derive"] }

core/src/cpu/disassembler.rs

@@ -1,6 +1,7 @@
 use crate::cpu::op::AddressingMode::*;
 use crate::cpu::op::{AddressingMode, Instruction};
 use crate::cpu::Cpu;
+use simplelog::debug;
 
 impl Cpu {
     pub fn disassemble_next_instr(&self) {
@@ -11,8 +12,8 @@ impl Cpu {
         let operation = instr.op().to_string();
         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}",
+        debug!(
+            "{:#04X} - ${:04X} {} {}\tA {:#04X}, X {:#04X}, Y {:#04X}, SP: {:#04X}, F: {:#04X}",
             op_code,
             registers.pc,
             operation,
@@ -30,19 +31,19 @@ impl Cpu {
         let byte_peek = (word_peek & 0xFF) as u8;
 
         match addr_mode {
-            ZP0 => format!("${:#02x}", byte_peek),
-            ZPX => format!("${:#02x},x", byte_peek),
-            ZPY => format!("${:#02x},x", byte_peek),
-            ABS => format!("${:#04x}", word_peek),
-            ABX => format!("${:#04x},x", word_peek),
-            ABY => format!("${:#04x},y", word_peek),
-            IND => format!("(${:#04x})", word_peek),
-            IDX => format!("(${:#02x},x)", word_peek),
-            IDY => format!("(${:#02x}),y", word_peek),
-            REL => format!("#${:#04x}", word_peek),
+            ZP0 => format!("${:04X}", byte_peek),
+            ZPX => format!("${:04X},x", byte_peek),
+            ZPY => format!("${:04X},x", byte_peek),
+            ABS => format!("${:04X}", word_peek),
+            ABX => format!("${:04X},x", word_peek),
+            ABY => format!("${:04X},y", word_peek),
+            IND => format!("(${:04X})", word_peek),
+            IDX => format!("(${:04X},x)", word_peek),
+            IDY => format!("(${:04X}),y", word_peek),
+            REL => format!("#${:04X}", word_peek),
             ACC => String::from('A'),
-            IMP => String::from(""),
-            IMM => format!("{:#02x}", byte_peek),
+            IMP => String::from("I"),
+            IMM => format!("{:04X}", byte_peek),
         }
     }
 }

core/src/cpu/mod.rs

@@ -2,12 +2,15 @@ mod disassembler;
 mod op;
 mod operations;
 
-use std::cell::RefCell;
-use std::rc::Rc;
 use crate::memory::MemoryBus;
 use crate::Clock;
+use std::cell::RefCell;
+use std::rc::Rc;
 use bitflags::bitflags;
+use simplelog::debug;
 
+const INITIAL_PC_ADDRESS: u16 = 0xFFFC;
+const NMI_HANDLER_ADDRESS: u16 = 0xFFFA;
 const STACK_ADDR: u16 = 0x0100;
 
 /// Represents a 6502 CPU
@@ -151,6 +154,25 @@ impl Cpu {
             nmi_requested: false,
         }
     }
+
+    pub fn initialize(&mut self) {
+        let init_pc = self.memory_bus.borrow().get_word(INITIAL_PC_ADDRESS);
+        self.registers.pc = init_pc;
+        debug!("Initialized CPU to PC ${:#04x}", init_pc);
+    }
+
+    fn process_nmi(&mut self) {
+        let handler_addr = self.memory_bus.borrow().get_word(NMI_HANDLER_ADDRESS);
+        debug!("NMI, PC -> {:#04x}", handler_addr);
+
+        self.stack_push_context();
+        self.nmi_requested = false;
+        self.registers.pc = handler_addr;
+    }
+
+    fn process_oam(&mut self) {
+        todo!();
+    }
 }
 
 impl CpuInternals for Cpu {
@@ -259,6 +281,12 @@ impl Clock for Cpu {
         self.busy_cycle_count = instr.cycles();
         self.exec_instruction(instr);
 
-        // TODO: NMI, OAM DMA
+        if self.nmi_requested {
+            self.process_nmi();
+        }
+
+        if self.oam_dma_triggered {
+            self.process_oam();
+        }
     }
 }

core/src/cpu/op.rs

@@ -125,6 +125,8 @@ impl Cpu {
             Self::operand_decode_acc()
         } else if addr_mode == IMM {
             self.operand_decode_immediate()
+        } else if addr_mode == IMP {
+            self.operand_decode_implicit()
         } else {
             // Other modes are addresses
             let mut page_crossed = false;
@@ -168,6 +170,14 @@ impl Cpu {
         }
     }
 
+    fn operand_decode_implicit(&self) -> Operand {
+        Operand {
+            operand_type: OperandType::Immediate,
+            value: 0,
+            is_page_crossing: false,
+        }
+    }
+
     /// d - byte % 256
     fn operand_addr_zp(&mut self) -> u16 {
         self.program_get_next_byte() as u16

core/src/lib.rs

@@ -3,6 +3,7 @@ mod mappers;
 mod memory;
 mod rom;
 pub mod system;
+mod ppu;
 
 pub trait Clock {
     /// Run a clock cycle

core/src/memory.rs

@@ -37,9 +37,11 @@ impl MemoryBus {
         } else if addr < PPU_MAX_ADDR {
             let relative_addr = addr - RAM_MAX_ADDR;
             let ppu_register = relative_addr % 8;
-            todo!()
+            // todo!()
+            0
         } else if addr < APU_MAX_ADDR {
-            todo!()
+            // todo!()
+            0
         } else if addr < UNMAPPED_MAX_ADDR {
             assert!(false);
             0
@@ -63,7 +65,10 @@ impl MemoryBus {
     /// # Arguments
     ///  * `addr` - The address of the word
     pub fn get_word(&self, addr: u16) -> u16 {
-        unimplemented!("MemoryBus::get_word");
+        let low = self.get_byte(addr) as u16;
+        let high = self.get_byte(addr + 1) as u16;
+
+        (high << 8) | low
     }
 
     /// Sets a byte in memory
@@ -72,6 +77,22 @@ impl MemoryBus {
     ///  * `addr` - The address of the byte
     ///  * `value` - The value to set
     pub fn set_byte(&mut self, addr: u16, value: u8) {
-        unimplemented!("MemoryBus::set_byte");
+        assert!(addr < MEMORY_MAX_ADDR);
+        if addr < RAM_MAX_ADDR {
+            let ram_addr = (addr as usize) % RAM_SIZE;
+            self.ram[ram_addr] = value;
+        } else if addr < PPU_MAX_ADDR {
+            let relative_addr = addr - RAM_MAX_ADDR;
+            let ppu_register = relative_addr % 8;
+            // todo!()
+        } else if addr < APU_MAX_ADDR {
+        } else if addr < UNMAPPED_MAX_ADDR {
+            assert!(false);
+        } else if addr < CARTRIDGE_RAM_MAX_ADDR {
+            assert!(false);
+        } else {
+            // Cannot write to ROM
+            assert!(false);
+        }
     }
 }

core/src/ppu/mod.rs

@@ -0,0 +1,20 @@
+use crate::memory::MemoryBus;
+use crate::Clock;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+pub struct Ppu {
+    memory_bus: Rc<RefCell<MemoryBus>>,
+}
+
+impl Ppu {
+    pub fn new(memory_bus: Rc<RefCell<MemoryBus>>) -> Self {
+        Self { memory_bus }
+    }
+}
+
+impl Clock for Ppu {
+    fn cycle(&mut self) {
+        // todo!()
+    }
+}

core/src/system.rs

@@ -1,34 +1,56 @@
+use simplelog::info;
 use std::cell::RefCell;
 use std::rc::Rc;
-use simplelog::info;
 use crate::cpu::Cpu;
 use crate::mappers::get_mapper;
 use crate::memory::MemoryBus;
 use crate::rom::{Rom, RomReadError};
+use crate::Clock;
+use crate::ppu::Ppu;
+
+const CPU_CLOCK_DIVISOR: usize = 12;
+const CPU_CYCLE_PER_REFRESH: usize = MASTER_CYCLE_PER_REFRESH / CPU_CLOCK_DIVISOR;
+const MASTER_CLOCK: usize = 21477272; // NTSC NES Master Clock (~21.47 MHz)
+const MASTER_CYCLE_PER_REFRESH: usize = MASTER_CLOCK / REFRESH_RATE;
+const PPU_CLOCK_DIVISOR: usize = 4;
+const PPU_CYCLE_PER_REFRESH: usize = CPU_CLOCK_DIVISOR / PPU_CLOCK_DIVISOR;
+const REFRESH_RATE: usize = 60; // 60 Hz
 
 pub struct System {
     cpu: Cpu,
     memory_bus: Rc<RefCell<MemoryBus>>,
+    ppu: Ppu
 }
 
 impl System {
     pub fn new() -> Self {
         let memory_bus = Rc::new(RefCell::new(MemoryBus::new()));
         let cpu = Cpu::new(Rc::clone(&memory_bus));
-        
-        Self {
-            cpu,
-            memory_bus
-        }
+        let ppu = Ppu::new(Rc::clone(&memory_bus));
+
+        Self { cpu, memory_bus, ppu }
     }
 
-    pub fn insert_rom(&self, path: &str) -> Result<(), RomReadError> {
+    pub fn insert_rom(&mut self, path: &str) -> Result<(), RomReadError> {
         let rom = Rom::read(path)?;
         let mapper = get_mapper(rom);
 
         self.memory_bus.borrow_mut().register_mapper(mapper);
+        self.cpu.initialize();
 
         info!("Successfully inserted ROM into system");
         Ok(())
     }
-}
+}
+
+impl Clock for System {
+    fn cycle(&mut self) {
+        for _cpu_cycle in 0usize..CPU_CYCLE_PER_REFRESH {
+            self.cpu.cycle();
+
+            for _ppu_cycle in 0usize..PPU_CYCLE_PER_REFRESH {
+                self.ppu.cycle();
+            }
+        }
+    }
+}

ui/src/main.rs

@@ -1,4 +1,7 @@
+use std::thread::sleep;
+use std::time::Duration;
 use core::system::System;
+use core::Clock;
 use simplelog::*;
 
 const ROM_PATH: &'static str = "./roms/dk.nes";
@@ -15,5 +18,10 @@ fn main() {
     let mut system = System::new();
     system.insert_rom(ROM_PATH).expect("Failed to insert ROM");
 
-    print!("Do stuff");
+    loop {
+        system.cycle();
+
+        // TODO: Inaccurate, ~60hz
+        sleep(Duration::from_millis(16));
+    }
 }