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fix: allow for the ppu to modify interrupt flags

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This commit is contained in:
Rekai Nyangadzayi Musuka
2021-03-20 19:53:56 -05:00
parent f45c2439c1
commit f365633c1e
2 changed files with 67 additions and 3 deletions
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42
src/bus.rs
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@@ -1,7 +1,7 @@
use super::cartridge::Cartridge;
use super::high_ram::HighRam;
use super::instruction::Cycles;
use super::interrupt::Interrupt;
use super::interrupt::{Interrupt, InterruptFlag};
use super::ppu::Ppu;
use super::serial::Serial;
use super::sound::Sound;
@@ -118,7 +118,7 @@ impl Bus {
0xFF01 => self.serial.next,
0xFF02 => self.serial.control.into(),
0xFF07 => self.timer.control.into(),
0xFF0F => self.interrupt.flag.into(),
0xFF0F => self.interrupt_flag().into(),
0xFF11 => self.sound.ch1.sound_duty.into(),
0xFF12 => self.sound.ch1.vol_envelope.into(),
0xFF14 => self.sound.ch1.freq_hi.into(),
@@ -203,7 +203,7 @@ impl Bus {
0xFF01 => self.serial.next = byte,
0xFF02 => self.serial.control = byte.into(),
0xFF07 => self.timer.control = byte.into(),
0xFF0F => self.interrupt.flag = byte.into(),
0xFF0F => self.set_interrupt_flag(byte),
0xFF11 => self.sound.ch1.sound_duty = byte.into(),
0xFF12 => self.sound.ch1.vol_envelope = byte.into(),
0xFF13 => self.sound.ch1.freq_lo = byte.into(),
@@ -251,3 +251,39 @@ impl Bus {
self.write_byte(addr, (word & 0x00FF) as u8);
}
}
impl Bus {
fn interrupt_flag(&self) -> InterruptFlag {
// Read the current Interrupt status from the PPU
let ppu_vblank = self.ppu.interrupt.vblank();
let ppu_lcd_stat = self.ppu.interrupt.lcd_stat();
// We actually don't care about what the InterruptFlag currently says
// about vblank and lcd_stat, because the PPU has the more accurate
// knowledge about what state these interrupt flags are in.
// In order to have the PPU be the source of truth
// (and accounting for the fact that we aren't able to update)
// the interrupt flag register 0xFF0F in the method, we can
// mask over those two interruptss
// Copy the Interrupt Flag register 0xFF0F
let mut flag = self.interrupt.flag;
flag.set_vblank(ppu_vblank);
flag.set_lcd_stat(ppu_lcd_stat);
flag
}
fn set_interrupt_flag(&mut self, byte: u8) {
// Update the Interrupt register 0xFF0F
self.interrupt.flag = byte.into();
let vblank = self.interrupt.flag.vblank();
let lcd_stat = self.interrupt.flag.lcd_stat();
// Update the PPU's internal tracking of the interrupt register 0xFF0F
self.ppu.interrupt.set_vblank(vblank);
self.ppu.interrupt.set_lcd_stat(lcd_stat);
}
}