Minor refactors and bug fixes

- Bit instruction now sets Z flag correctly
- DMA is no longer handled by cpu.rs

src/cpu.rs

@@ -1,7 +1,7 @@
 use std::fmt::Write;
 use tracing::debug;
 
-use crate::{debug::DebugLog, mem::CpuMem};
+use crate::{Break, debug::DebugLog, mem::CpuMem};
 
 bitfield::bitfield! {
     #[derive(Clone, Copy, PartialEq, Eq)]
@@ -634,7 +634,9 @@ impl Cpu {
                 if self.status.carry() {
                     let page = self.jmp_rel(off);
                     log!("    : - JMP ${:04X}", self.pc);
-                    if page { return ExecState::PageCross };
+                    if page {
+                        return ExecState::PageCross;
+                    };
                 }
             }),
             0xF0 => inst!("BEQ", self.status.zero(), |off| {
@@ -642,7 +644,9 @@ impl Cpu {
                 if self.status.zero() {
                     let page = self.jmp_rel(off);
                     log!("    : - JMP ${:04X}", self.pc);
-                    if page { return ExecState::PageCross };
+                    if page {
+                        return ExecState::PageCross;
+                    };
                 }
             }),
             0x30 => inst!("BMI", self.status.negative(), |off| {
@@ -650,7 +654,9 @@ impl Cpu {
                 if self.status.negative() {
                     let page = self.jmp_rel(off);
                     log!("    : - JMP ${:04X}", self.pc);
-                    if page { return ExecState::PageCross };
+                    if page {
+                        return ExecState::PageCross;
+                    };
                 }
             }),
             0xD0 => inst!("BNE", !self.status.zero(), |off| {
@@ -658,7 +664,9 @@ impl Cpu {
                 if !self.status.zero() {
                     let page = self.jmp_rel(off);
                     log!("    : - JMP ${:04X}", self.pc);
-                    if page { return ExecState::PageCross };
+                    if page {
+                        return ExecState::PageCross;
+                    };
                 }
             }),
             0x10 => inst!("BPL", !self.status.negative(), |off| {
@@ -666,7 +674,9 @@ impl Cpu {
                 if !self.status.negative() {
                     let page = self.jmp_rel(off);
                     log!("    : - JMP ${:04X}", self.pc);
-                    if page { return ExecState::PageCross };
+                    if page {
+                        return ExecState::PageCross;
+                    };
                 }
             }),
             0x4C => inst!("JMP abs", 0, |low, high| {
@@ -1509,14 +1519,14 @@ impl Cpu {
             }),
             0x24 => inst!("BIT zp", 1, |off| {
                 let val = self.read_abs(mem, off, 0);
-                self.status.set_zero(val == 0);
+                self.status.set_zero(val & self.a == 0);
                 self.status.set_overflow(val & 0x40 == 0x40);
                 self.status.set_negative(val & 0x80 == 0x80);
                 log!("{addr:04X}: BIT ${:02X} | {:02X}", off, val);
             }),
             0x2C => inst!("BIT abs", 1, |low, high| {
                 let val = self.read_abs(mem, low, high);
-                self.status.set_zero(val == 0);
+                self.status.set_zero(val & self.a == 0);
                 self.status.set_overflow(val & 0x40 == 0x40);
                 self.status.set_negative(val & 0x80 == 0x80);
                 log!("{addr:04X}: BIT ${:02X}{:02X} | {:02X}", high, low, val);
@@ -1723,7 +1733,7 @@ impl Cpu {
         }
     }
 
-    fn clock_cpu(&mut self, mem: &mut CpuMem<'_>, nmi: bool, irq: bool) {
+    pub fn clock_cpu(&mut self, mem: &mut CpuMem<'_>, nmi: bool, irq: bool, br: &Break) -> bool {
         self.clock_state = match self.clock_state {
             ClockState::HoldNmi { cycles } => {
                 if cycles == 0 {
@@ -1750,6 +1760,10 @@ impl Cpu {
                 }
             }
             ClockState::ReadInstruction => {
+                if br.cpu_exec {
+                    println!("Returning early from clock_cpu");
+                    return true;
+                }
                 let addr = self.pc;
                 let instruction = mem.read(self.pc);
                 if instruction != 0x02 {
@@ -1900,59 +1914,13 @@ impl Cpu {
         }
         // self.irq_pending = self.ppu.irq_waiting() || self.apu.irq_waiting();
         self.irq_pending = irq;
+        false
     }
 
-    pub fn cpu_cycle(
-        &mut self,
-        mem: &mut CpuMem<'_>,
-        dma: &mut DmaState,
-        nmi: bool,
-        irq: bool,
-    ) {
-        match *dma {
-            DmaState::Passive => self.clock_cpu(mem, nmi, irq),
-            // TODO: Validate that this takes the correct number of cycles (513 or 514 cycles)
-            DmaState::Running {
-                cpu_addr,
-                rem,
-                read: Some(read),
-            } => {
-                mem.write(0x2004, read);
-                // self.ppu.write_reg(4, read);
-                debug!("OAM DMA write {:02X}", read);
-                if rem == 0 {
-                    *dma = DmaState::Passive;
-                } else {
-                    *dma = DmaState::Running {
-                        cpu_addr: cpu_addr + 1,
-                        rem: rem - 1,
-                        read: None,
-                    };
-                }
-            }
-            DmaState::Running {
-                cpu_addr,
-                rem,
-                read: None,
-            } => {
-                let read = mem.read(cpu_addr);
-                debug!("OAM DMA read {:04X} {:02X}", cpu_addr, read);
-                *dma = DmaState::Running {
-                    cpu_addr,
-                    rem,
-                    read: Some(read),
-                };
-            }
-        }
-        // if [0x8031, 0x8014].contains(&self.cpu.pc) {
-        //     self.dbg_int = true;
-        // }
-    }
     pub fn cpu_cycle_update(&mut self) {
         if !self.halted {
             self.cycle += 1;
         }
-        
     }
 
     pub fn executed(&self) -> bool {
@@ -1978,6 +1946,7 @@ impl Cpu {
 #[derive(Debug, Clone, Copy)]
 pub enum DmaState {
     Passive,
+    Idle(u16),
     Running {
         cpu_addr: u16,
         rem: u8,
@@ -1995,6 +1964,56 @@ impl DmaState {
             }
         }
     }
+
+    pub fn cycle(self, mem: &mut CpuMem<'_>, cpu: &mut Cpu) -> Option<Self> {
+        match self {
+            DmaState::Passive => None,
+            DmaState::Idle(cpu_addr) => Some(DmaState::Running {
+                cpu_addr,
+                rem: 0xFF,
+                read: None,
+            }),
+            DmaState::Running {
+                cpu_addr,
+                rem,
+                read: Some(read),
+            } => {
+                mem.write(0x2004, read);
+                // self.ppu.write_reg(4, read);
+                writeln!(&mut cpu.debug_log, "OAM DMA write {:02X}", read).unwrap();
+                if rem == 0 {
+                    Some(DmaState::Passive)
+                } else {
+                    Some(DmaState::Running {
+                        cpu_addr: cpu_addr + 1,
+                        rem: rem - 1,
+                        read: None,
+                    })
+                }
+            }
+            DmaState::Running {
+                cpu_addr,
+                rem,
+                read: None,
+            } => {
+                if cpu.cycle % 2 != 1 {
+                    return Some(self);
+                }
+                let read = mem.read(cpu_addr);
+                writeln!(
+                    &mut cpu.debug_log,
+                    "OAM DMA read {:04X} {:02X}",
+                    cpu_addr, read
+                )
+                .unwrap();
+                Some(DmaState::Running {
+                    cpu_addr,
+                    rem,
+                    read: Some(read),
+                })
+            }
+        }
+    }
 }
 
 pub struct CycleResult {

src/debugger.rs

@@ -24,7 +24,7 @@ use iced::{
     },
 };
 
-use crate::{CycleResult, NES, PPU, mem::Mapped};
+use crate::{Break, CycleResult, NES, PPU, mem::Mapped};
 
 #[derive(Debug, Clone)]
 pub struct DebuggerState {
@@ -254,23 +254,41 @@ impl DebuggerState {
 
     fn run_n_clock_cycles(nes: &mut NES, n: usize) {
         for _ in 0..n {
-            if nes.run_one_clock_cycle().dbg_int || nes.halted() {
+            if nes.run_one_clock_cycle(&Break::default()).dbg_int || nes.halted() {
                 break;
             }
         }
     }
-    fn run_until(nes: &mut NES, mut f: impl FnMut(CycleResult, &NES) -> bool, mut count: usize) {
-        loop {
-            let res = nes.run_one_clock_cycle();
-            if res.dbg_int || f(res, nes) {
+    fn run_until(
+        nes: &mut NES,
+        br: &Break,
+        mut f: impl FnMut(CycleResult, &NES) -> bool,
+        // mut count: usize,
+    ) {
+        // Always run at least 1 cycle
+        let mut res = nes.run_one_clock_cycle(&Break::default());
+        while !nes.halted() && !res.dbg_int && !f(res, nes) {
+            // if res.dbg_int || f(res, nes) {
+            //     count -= 1;
+            //     if count <= 0 {
+            //         break;
+            //     }
+            // }
+            // if nes.halted() {
+            //     break;
+            // }
+            res = nes.run_one_clock_cycle(br);
+        }
+    }
+    fn run_until_n(
+        nes: &mut NES,
+        br: &Break,
+        mut f: impl FnMut(CycleResult, &NES) -> bool,
+        mut count: usize,
+    ) {
+        while count > 0 {
+            Self::run_until(nes, br, &mut f);
             count -= 1;
-                if count <= 0 {
-                    break;
-                }
-            }
-            if nes.halted() {
-                break;
-            }
         }
     }
 
@@ -280,23 +298,49 @@ impl DebuggerState {
             DebuggerMessage::SetCPUCycles(n) => self.cpu_cycles = n,
             DebuggerMessage::SetInstructions(n) => self.instructions = n,
             DebuggerMessage::SetScanLines(n) => self.scan_lines = n,
-            DebuggerMessage::SetToScanLine(n) => self.to_scan_line = n,
+            DebuggerMessage::SetToScanLine(n) => self.to_scan_line = n.min(261), // Max scanline is 261
             DebuggerMessage::SetFrames(n) => self.frames = n,
             DebuggerMessage::SetBreakpoint(n) => self.breakpoint = n,
             DebuggerMessage::RunPPUCycles => Self::run_n_clock_cycles(nes, self.ppu_cycles),
             DebuggerMessage::RunCPUCycles => Self::run_n_clock_cycles(nes, self.cpu_cycles * 3),
-            DebuggerMessage::RunInstructions => {
-                Self::run_until(nes, |c, _| c.cpu_exec, self.instructions)
-            }
+            // DebuggerMessage::RunInstructions => Self::run_until_n(
+            //     nes,
+            //     &Break {
+            //         cpu_exec: true,
+            //         ..Break::default()
+            //     },
+            //     |_, _| false,
+            //     self.instructions,
+            // ),
+            DebuggerMessage::RunInstructions => Self::run_until_n(
+                nes,
+                &Break {
+                    ..Break::default()
+                },
+                |res, _| res.cpu_exec,
+                self.instructions,
+            ),
             DebuggerMessage::RunScanLines => Self::run_n_clock_cycles(nes, self.scan_lines * 341),
-            DebuggerMessage::RunToScanLine => {
-                Self::run_until(nes, |_, n| n.ppu.scanline == self.to_scan_line, 1)
-            }
+            DebuggerMessage::RunToScanLine => Self::run_until(
+                nes,
+                &Break {
+                    ppu_scanline: true,
+                    ..Break::default()
+                },
+                |_, n| n.ppu.scanline == self.to_scan_line,
+            ),
             DebuggerMessage::RunFrames => Self::run_n_clock_cycles(nes, self.frames * 341 * 262),
-            DebuggerMessage::RunBreakpoint => {
-                Self::run_until(nes, |_, nes| nes.cpu.pc as usize == self.breakpoint, 1)
+            DebuggerMessage::RunBreakpoint => Self::run_until(
+                nes,
+                &Break {
+                    break_points: vec![self.breakpoint as u16],
+                    ..Break::default()
+                },
+                |_, nes| nes.cpu.pc as usize == self.breakpoint,
+            ),
+            DebuggerMessage::Run => {
+                Self::run_until(nes, &Break { ..Break::default() }, |_, nes| nes.halted())
             }
-            DebuggerMessage::Run => Self::run_until(nes, |_, nes| nes.halted(), 1),
             DebuggerMessage::Pause => todo!(),
         }
     }

src/hex_view.rs

@@ -7,18 +7,24 @@ use iced::{
     widget::{column, lazy, row, text},
 };
 
-use crate::mem::Mapped;
+use crate::{mem::Mapped, PPU};
 
 pub trait Memory {
-    fn peek(&self, val: u16) -> Option<u8>;
+    fn peek(&self, val: usize) -> Option<u8>;
+    fn len(&self) -> usize;
     fn edit_ver(&self) -> usize;
 }
 
+#[derive(Debug, Clone, Copy)]
 pub struct Cpu<'a>(pub &'a Mapped);
 
 impl Memory for Cpu<'_> {
-    fn peek(&self, val: u16) -> Option<u8> {
-        self.0.peek_cpu(val)
+    fn peek(&self, val: usize) -> Option<u8> {
+        self.0.peek_cpu(val as u16)
+    }
+
+    fn len(&self) -> usize {
+        0x10000
     }
 
     fn edit_ver(&self) -> usize {
@@ -26,11 +32,16 @@ impl Memory for Cpu<'_> {
     }
 }
 
+#[derive(Debug, Clone, Copy)]
 pub struct Ppu<'a>(pub &'a Mapped);
 
 impl Memory for Ppu<'_> {
-    fn peek(&self, val: u16) -> Option<u8> {
-        self.0.peek_ppu(val)
+    fn peek(&self, val: usize) -> Option<u8> {
+        self.0.peek_ppu(val as u16)
+    }
+
+    fn len(&self) -> usize {
+        0x10000
     }
 
     fn edit_ver(&self) -> usize {
@@ -38,6 +49,23 @@ impl Memory for Ppu<'_> {
     }
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct Oam<'a>(pub &'a PPU);
+
+impl Memory for Oam<'_> {
+    fn peek(&self, val: usize) -> Option<u8> {
+        Some(self.0.peek_oam(val as u8))
+    }
+
+    fn len(&self) -> usize {
+        0x100
+    }
+
+    fn edit_ver(&self) -> usize {
+        self.0.oam_edit_ver()
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum HexEvent {}
 
@@ -60,29 +88,13 @@ impl HexView {
         Self {}
     }
 
-    pub fn render<'a>(&self, mem: &'a Mapped, ppu: bool) -> Element<'a, HexEvent> {
-        struct Row<'a>(u16, &'a Mapped, bool);
-        impl fmt::Display for Row<'_> {
+    pub fn render_any<'a, M: Memory + Copy + 'a>(&self, mem: M) -> Element<'a, HexEvent> {
+        struct Row<M: Memory>(usize, M);
+        impl<'a, M: Memory + 'a> fmt::Display for Row<M> {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-                write!(
-                    f,
-                    "{}",
-                    Val(if self.2 {
-                        self.1.peek_ppu(self.0)
-                    } else {
-                        self.1.peek_cpu(self.0)
-                    })
-                )?;
+                write!(f, "{}", Val(self.1.peek(self.0)))?;
                 for i in 1..16 {
-                    write!(
-                        f,
-                        " {}",
-                        Val(if self.2 {
-                            self.1.peek_ppu(self.0 + i)
-                        } else {
-                            self.1.peek_cpu(self.0 + i)
-                        })
-                    )?;
+                    write!(f, " {}", Val(self.1.peek(self.0 + i)))?;
                 }
                 Ok(())
             }
@@ -90,11 +102,7 @@ impl HexView {
         column![
             text!("Hex view"),
             iced::widget::scrollable(lazy(
-                if ppu {
-                    mem.ppu_edit_ver()
-                } else {
-                    mem.cpu_edit_ver()
-                },
+                mem.edit_ver(),
                 move |_| column(
                     [
                         text!("      | 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F")
@@ -102,8 +110,8 @@ impl HexView {
                             .into()
                     ]
                     .into_iter()
-                    .chain((0..u16::MAX).step_by(16).map(|off| {
-                        text!(" {off:04X} | {}", Row(off, mem, ppu))
+                    .chain((0..mem.len()).step_by(16).map(|off| {
+                        text!(" {off:04X} | {}", Row(off, mem))
                             .font(Font::MONOSPACE)
                             .into()
                     }))
@@ -114,6 +122,15 @@ impl HexView {
         .width(Fill)
         .into()
     }
+    pub fn render_cpu<'a>(&self, mem: &'a Mapped) -> Element<'a, HexEvent> {
+        self.render_any(Cpu(mem))
+    }
+    pub fn render_ppu<'a>(&self, mem: &'a Mapped) -> Element<'a, HexEvent> {
+        self.render_any(Ppu(mem))
+    }
+    pub fn render_oam<'a>(&self, ppu: &'a PPU) -> Element<'a, HexEvent> {
+        self.render_any(Oam(ppu))
+    }
 
     pub fn update(&mut self, ev: HexEvent) -> Task<HexEvent> {
         todo!()

src/lib.rs

@@ -163,7 +163,45 @@ impl NES {
         self.ppu.peek_irq() || self.apu.peek_irq()
     }
 
-    pub fn run_one_clock_cycle(&mut self) -> CycleResult {
+    pub fn run_cpu_cycle(
+        &mut self,
+        // mem: &mut CpuMem<'_>,
+        // dma: &mut DmaState,
+        // nmi: bool,
+        // irq: bool,
+        br: &Break,
+    ) -> bool {
+        if let Some(dma) = self.dma.cycle(
+                &mut CpuMem::new(
+                    &mut self.mapped,
+                    &mut self.ppu,
+                    &mut self.apu,
+                    &mut self.dma,
+                    &mut self.controller,
+                ),
+                &mut self.cpu
+        ) {
+            self.dma = dma;
+            false
+        } else {
+            let nmi = self.ppu.nmi_waiting() || self.apu.nmi_waiting();
+            let irq = self.ppu.irq_waiting() || self.apu.irq_waiting();
+            self.cpu.clock_cpu(
+                &mut CpuMem::new(
+                    &mut self.mapped,
+                    &mut self.ppu,
+                    &mut self.apu,
+                    &mut self.dma,
+                    &mut self.controller,
+                ),
+                nmi,
+                irq,
+                br,
+            )
+        }
+    }
+
+    pub fn run_one_clock_cycle(&mut self, br: &Break) -> CycleResult {
         if self.cpu.halted() {
             return CycleResult {
                 cpu_exec: false,
@@ -172,31 +210,40 @@ impl NES {
                 dbg_int: true,
             };
         }
-        self.clock_count += 1;
-        let cpu_exec = if self.clock_count % 3 == 0 {
+        let cpu_exec = if self.clock_count % 3 == 0 && self.clock_count > 0 {
             let nmi = self.ppu.nmi_waiting() || self.apu.nmi_waiting();
             let irq = self.ppu.irq_waiting() || self.apu.irq_waiting();
             let mut dma = DmaState::Passive;
-            self.cpu.cpu_cycle(
-                &mut CpuMem::new(
-                    &mut self.mapped,
-                    &mut self.ppu,
-                    &mut self.apu,
-                    &mut dma,
-                    &mut self.controller,
-                ),
-                &mut self.dma,
-                nmi,
-                irq,
-            );
+            if self.run_cpu_cycle(
+                // &mut CpuMem::new(
+                //     &mut self.mapped,
+                //     &mut self.ppu,
+                //     &mut self.apu,
+                //     &mut dma,
+                //     &mut self.controller,
+                // ),
+                // &mut self.dma,
+                // nmi,
+                // irq,
+                br,
+            ) {
+                println!("Returning early from clock_cycle");
+                return CycleResult {
+                    cpu_exec: true,
+                    ppu_frame: false,
+                    dma: false,
+                    dbg_int: true,
+                };
+            }
             self.dma.merge(dma);
+            self.cpu.cpu_cycle_update();
             self.cpu.executed()
+        } else if self.clock_count == 0 {
+            self.cpu.cpu_cycle_update();
+            false
         } else {
             false
         };
-        if self.clock_count % 3 == 1 {
-            self.cpu.cpu_cycle_update();
-        }
         // let cpu_exec = self.clock_count % 3 == CPU_CLOCK_OFFSET && self.cpu.executed();
         if !self.cpu.halted() {
             let _apu_exec = self.apu.run_one_clock_cycle(self.clock_count);
@@ -211,6 +258,7 @@ impl NES {
         let dbg_int = self.dbg_int | self.ppu.dbg_int;
         self.dbg_int = false;
         self.ppu.dbg_int = false;
+        self.clock_count += 1;
         CycleResult {
             cpu_exec,
             ppu_frame,
@@ -243,7 +291,7 @@ impl NES {
         self.reset();
         while !self.cpu.halted() {
             // info!("Running clock cycle: {}", self.clock_count);
-            self.run_one_clock_cycle();
+            self.run_one_clock_cycle(&Break::default());
         }
     }
 
@@ -281,7 +329,7 @@ impl NES {
         let mut cur = 0;
         while !self.cpu.halted() && cur < max_clock_cycles {
             // info!("Running clock cycle: {}", self.clock_count);
-            self.run_one_clock_cycle();
+            self.run_one_clock_cycle(&Break::default());
             cur += 1;
         }
     }
@@ -326,3 +374,16 @@ impl NES {
         self.cpu.cycle
     }
 }
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
+pub struct Break {
+    pub dma: bool,
+    pub nmi: bool,
+    pub irq: bool,
+    pub cpu_exec: bool,
+    pub ppu_frame: bool,
+    pub ppu_scanline: bool,
+    pub break_points: Vec<u16>,
+    // pub dma: bool,
+    // pub dbg_int: bool,
+}

src/main.rs

@@ -51,6 +51,7 @@ fn main() -> Result<(), iced::Error> {
 enum MemoryTy {
     Cpu,
     PPU,
+    OAM,
 }
 
 impl fmt::Display for MemoryTy {
@@ -86,6 +87,7 @@ impl fmt::Display for HeaderButton {
         match self {
             Self::Open(WindowType::Memory(MemoryTy::Cpu, _)) => write!(f, "Open Memory Viewer"),
             Self::Open(WindowType::Memory(MemoryTy::PPU, _)) => write!(f, "Open PPU Memory Viewer"),
+            Self::Open(WindowType::Memory(MemoryTy::OAM, _)) => write!(f, "Open OAM Memory Viewer"),
             Self::Open(WindowType::TileMap) => write!(f, "Open TileMap Viewer"),
             Self::Open(WindowType::TileViewer) => write!(f, "Open Tile Viewer"),
             Self::Open(WindowType::Debugger) => write!(f, "Open Debugger"),
@@ -108,11 +110,11 @@ struct Emulator {
 #[derive(Debug, Clone)]
 enum Message {
     OpenRom(NES),
-    Tick(usize),
-    Frame,
-    DMA,
-    CPU,
-    DebugInt,
+    // Tick(usize),
+    // Frame,
+    // DMA,
+    // CPU,
+    // DebugInt,
     WindowClosed(Id),
     WindowOpened(Id),
     Header(HeaderButton),
@@ -170,15 +172,15 @@ impl Emulator {
 
     fn update(&mut self, message: Message) -> Task<Message> {
         match message {
-            Message::Tick(count) => {
-                for _ in 0..count {
-                    self.nes.run_one_clock_cycle();
-                }
-            }
-            Message::Frame => while !self.nes.run_one_clock_cycle().ppu_frame {},
-            Message::DMA => while !self.nes.run_one_clock_cycle().dma {},
-            Message::CPU => while !self.nes.run_one_clock_cycle().cpu_exec {},
-            Message::DebugInt => while !self.nes.run_one_clock_cycle().dbg_int {},
+            // Message::Tick(count) => {
+            //     for _ in 0..count {
+            //         self.nes.run_one_clock_cycle();
+            //     }
+            // }
+            // Message::Frame => while !self.nes.run_one_clock_cycle().ppu_frame {},
+            // Message::DMA => while !self.nes.run_one_clock_cycle().dma {},
+            // Message::CPU => while !self.nes.run_one_clock_cycle().cpu_exec {},
+            // Message::DebugInt => while !self.nes.run_one_clock_cycle().dbg_int {},
             Message::WindowClosed(id) => {
                 if let Some(WindowType::Main) = self.windows.remove(&id) {
                     return iced::exit();
@@ -238,8 +240,13 @@ impl Emulator {
             }
             Message::Export(ty) => {
                 let raw: Vec<_> = match ty {
-                    MemoryTy::Cpu => (0..=0xFFFF).map(|i| self.nes.mem().peek_cpu(i).unwrap_or(0)).collect(),
-                    MemoryTy::PPU => (0..=0xFFFF).map(|i| self.nes.mem().peek_ppu(i).unwrap_or(0)).collect(),
+                    MemoryTy::Cpu => (0..=0xFFFF)
+                        .map(|i| self.nes.mem().peek_cpu(i).unwrap_or(0))
+                        .collect(),
+                    MemoryTy::PPU => (0..=0xFFFF)
+                        .map(|i| self.nes.mem().peek_ppu(i).unwrap_or(0))
+                        .collect(),
+                    MemoryTy::OAM => (0..=0xFF).map(|i| self.nes.ppu().peek_oam(i)).collect(),
                 };
                 return Task::future(async move {
                     if let Some(file) = rfd::AsyncFileDialog::new()
@@ -290,10 +297,13 @@ impl Emulator {
             Some(WindowType::Memory(ty, view)) => {
                 let hex = match ty {
                     MemoryTy::Cpu => view
-                        .render(self.nes.mem(), false)
+                        .render_cpu(self.nes.mem())
                         .map(move |e| Message::Hex(win, e)),
                     MemoryTy::PPU => view
-                        .render(self.nes.mem(), true)
+                        .render_ppu(self.nes.mem())
+                        .map(move |e| Message::Hex(win, e)),
+                    MemoryTy::OAM => view
+                        .render_oam(self.nes.ppu())
                         .map(move |e| Message::Hex(win, e)),
                 };
                 let content = column![row![header_menu("Export", [*ty], Message::Export)], hex]
@@ -338,6 +348,7 @@ impl Emulator {
                     HeaderButton::Open(WindowType::Debugger),
                     HeaderButton::Open(WindowType::Memory(MemoryTy::Cpu, HexView {})),
                     HeaderButton::Open(WindowType::Memory(MemoryTy::PPU, HexView {})),
+                    HeaderButton::Open(WindowType::Memory(MemoryTy::OAM, HexView {})),
                     HeaderButton::Open(WindowType::TileMap),
                     HeaderButton::Open(WindowType::TileViewer),
                     HeaderButton::Open(WindowType::Palette),

src/mem.rs

@@ -200,10 +200,8 @@ impl<R: Copy> MemoryMap<R> {
         }
         None
     }
-}
 
-impl<R> Memory for MemoryMap<R> {
-    fn peek(&self, addr: u16) -> Option<u8> {
+    fn peek_val(&self, addr: u16) -> Option<u8> {
         for segment in &self.segments {
             if segment.position <= addr && addr - segment.position < segment.size {
                 return match &segment.mem {
@@ -212,7 +210,7 @@ impl<R> Memory for MemoryMap<R> {
                     Data::Reg(_) => None,
                     Data::Mirror(pos) => {
                         let offset = addr - segment.position;
-                        self.peek(pos + offset)
+                        self.peek_val(pos + offset)
                     }
                     Data::Disabled => None,
                 };
@@ -220,6 +218,20 @@ impl<R> Memory for MemoryMap<R> {
         }
         None
     }
+}
+
+impl<R: Copy> Memory for MemoryMap<R> {
+    fn peek(&self, addr: usize) -> Option<u8> {
+        self.peek_val(addr as u16)
+    }
+
+    fn len(&self) -> usize {
+        self.segments
+            .iter()
+            .map(|s| s.position as usize + s.size as usize)
+            .max()
+            .unwrap_or(0)
+    }
 
     fn edit_ver(&self) -> usize {
         self.edit_ver
@@ -269,7 +281,7 @@ impl fmt::Display for SegmentId {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Mapped {
     cpu: MemoryMap<CPUMMRegisters>,
     ppu: MemoryMap<PPUMMRegisters>,
@@ -444,13 +456,13 @@ impl Mapped {
     }
 
     pub fn peek_ppu(&self, addr: u16) -> Option<u8> {
-        self.ppu.peek(addr)
+        self.ppu.peek_val(addr)
     }
     pub fn ppu_edit_ver(&self) -> usize {
         self.ppu.edit_ver
     }
     pub fn peek_cpu(&self, addr: u16) -> Option<u8> {
-        self.cpu.peek(addr)
+        self.cpu.peek_val(addr)
     }
     pub fn cpu_edit_ver(&self) -> usize {
         self.cpu.edit_ver
@@ -608,11 +620,7 @@ impl<'a> CpuMem<'a> {
             }
             Some((CPUMMRegisters::APU, offset, val)) => {
                 if offset == 0x014 {
-                    *self.dma = DmaState::Running {
-                        cpu_addr: (val as u16) << 8,
-                        rem: 0xFF,
-                        read: None,
-                    };
+                    *self.dma = DmaState::Idle((val as u16) << 8);
                 } else if offset == 0x16 {
                     self.controllers.write_joy_strobe(val);
                 } else {

src/ppu.rs

@@ -81,6 +81,7 @@ pub enum PPUMMRegisters {
 pub struct OAM {
     mem: Vec<u8>,
     addr: u8,
+    edit_ver: usize,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -565,6 +566,7 @@ impl PPU {
             oam: OAM {
                 mem: vec![0u8; 256],
                 addr: 0,
+                edit_ver: 0,
             },
         }
     }
@@ -603,7 +605,7 @@ impl PPU {
             _ => panic!("No register at {:02X}", offset),
         }
     }
-    pub fn write_reg(&mut self, mem: &mut PpuMem, offset: u16, val: u8) {
+    pub fn write_reg(&mut self, mem: &mut PpuMem, offset: u16, mut val: u8) {
         match offset {
             0x00 => {
                 self.nmi_enabled = val & 0b1000_0000 != 0;
@@ -631,8 +633,12 @@ impl PPU {
             }
             0x03 => self.oam.addr = val,
             0x04 => {
+                if self.oam.addr % 4 == 2 {
+                    val &= 0b11100011;
+                }
                 self.oam.mem[self.oam.addr as usize] = val;
                 self.oam.addr = self.oam.addr.wrapping_add(1);
+                self.oam.edit_ver += 1;
             }
             0x05 => {
                 if self.background.w {
@@ -865,6 +871,12 @@ impl PPU {
     pub fn irq_waiting(&mut self) -> bool {
         false
     }
+    pub fn peek_oam(&self, addr: u8) -> u8 {
+        self.oam.mem[addr as usize]
+    }
+    pub fn oam_edit_ver(&self) -> usize {
+        self.oam.edit_ver
+    }
 
     pub fn render_name_table<R: Renderer>(&self, mem: &Mapped, frame: &mut Frame<R>) {
         for y in 0..60 {

src/test_roms/alu_bit.s

@@ -0,0 +1,36 @@
+; Verifies that reset doesn't alter any RAM.
+
+.include "testing.s"
+
+zp_res VAL
+RAM = $300
+
+reset:
+	sei
+	cld
+	ldx #$FF
+	txs
+
+	lda #$F0
+	sta VAL
+	lda #$0F
+	bit VAL
+	php
+	pla
+	sta RAM+0
+
+	lda #$F0
+	sta $400
+	lda #$0F
+	bit $400
+	php
+	pla
+	sta RAM+1
+
+	stp
+
+nmi:
+	stp
+
+irq:
+	stp

src/test_roms/instructions.rs

@@ -61,3 +61,8 @@ rom_test!(implied_instructions, "implied_instrs.nes", |nes| {
     assert_eq!(nes.last_instruction(), "0x8026 HLT :2 []");
     assert_eq!(nes.cpu.a, 0x00);
 });
+
+rom_test!(bit, "alu_bit.nes", |nes| {
+    assert_eq!(nes.last_instruction(), "0x8021 HLT :2 []");
+    mem_cmp(&nes, 0x300, &[0xF6, 0xF6]);
+});

src/test_roms/mod.rs

@@ -1,5 +1,5 @@
 mod cpu_reset_ram;
-mod instr_test_v3;
+mod instructions;
 mod ppu;
 mod interrupts;