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fix(bus): improve guards for illlegal memory IO

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This commit is contained in:
Rekai Nyangadzayi Musuka
2021-06-06 21:17:48 -05:00
parent ef4e54aba6
commit c428e934d8
1 changed files with 26 additions and 16 deletions
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42
src/bus.rs
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@@ -115,7 +115,10 @@ impl BusIo for Bus {
},
0x8000..=0x9FFF => {
// 8KB Video RAM
self.ppu.read_byte(addr)
match self.ppu.stat.mode() {
PpuMode::VBlank => 0xFF,
_ => self.ppu.read_byte(addr),
}
}
0xA000..=0xBFFF => match self.cartridge.as_ref() {
// 8KB External RAM
@@ -146,18 +149,23 @@ impl BusIo for Bus {
_ => unreachable!("{:#06X} was incorrectly handled by ECHO RAM", addr),
}
}
0xFE00..=0xFE9F if self.ppu.dma.is_active() => 0xFF,
0xFE00..=0xFE9F => {
// Sprite Attribute Table
use PpuMode::{HBlank, VBlank};
match self.ppu.stat.mode() {
PpuMode::HBlank | PpuMode::VBlank => self.ppu.oam.read_byte(addr),
PpuMode::OamScan | PpuMode::Drawing => 0xFF,
HBlank | VBlank if !self.ppu.dma.is_active() => self.ppu.oam.read_byte(addr),
_ => 0xFF,
}
}
0xFEA0..=0xFEFF => {
// eprintln!("Read from {:#06X}, which is prohibited", addr);
// TODO: Properly Emulate what can happen here
0x00
// Prohibited Memory
use PpuMode::{HBlank, VBlank};
match self.ppu.stat.mode() {
HBlank | VBlank => 0x00,
_ => 0xFF, // TODO: OAM Sprite bug now occurs on the DMG
}
}
0xFF00..=0xFF7F => {
// IO Registers
@@ -224,7 +232,10 @@ impl BusIo for Bus {
}
0x8000..=0x9FFF => {
// 8KB Video RAM
self.ppu.write_byte(addr, byte);
match self.ppu.stat.mode() {
PpuMode::VBlank => {}
_ => self.ppu.write_byte(addr, byte),
}
}
0xA000..=0xBFFF => {
// 8KB External RAM
@@ -257,19 +268,18 @@ impl BusIo for Bus {
_ => unreachable!("{:#06X} was incorrectly handled by ECHO RAM", addr),
}
}
0xFE00..=0xFE9F if self.ppu.dma.is_active() => {}
0xFE00..=0xFE9F => {
// Sprite Attribute Table
use PpuMode::{HBlank, VBlank};
match self.ppu.stat.mode() {
PpuMode::HBlank | PpuMode::VBlank => self.ppu.oam.write_byte(addr, byte),
PpuMode::Drawing | PpuMode::OamScan => {}
HBlank | VBlank if !self.ppu.dma.is_active() => {
self.ppu.oam.write_byte(addr, byte)
}
_ => {}
}
}
0xFEA0..=0xFEFF => {
// eprintln!("Wrote {:#04X} to {:#06X}, which is prohibited", byte, addr);
// TODO: Properly emulate what can happen here
}
0xFEA0..=0xFEFF => {} // TODO: As far as I know, writes to here do nothing.
0xFF00..=0xFF7F => {
// IO Registers