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feat: implement Hblank and Vcount Interrupts

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Also implemented unique behaviour when writing to IF
This commit is contained in:
Rekai Nyangadzayi Musuka
2022-10-21 05:12:22 -03:00
parent d1fce8ba75
commit d30a4d7ee5
3 changed files with 67 additions and 14 deletions
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43
src/scheduler.zig
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@@ -25,8 +25,11 @@ pub const Scheduler = struct {
self.queue.deinit();
}
pub fn handleEvent(self: *Self, _: *Arm7tdmi, bus: *Bus) void {
pub fn handleEvent(self: *Self, cpu: *Arm7tdmi, bus: *Bus) void {
const should_handle = if (self.queue.peek()) |e| self.tick >= e.tick else false;
const stat = &bus.ppu.dispstat;
const vcount = &bus.ppu.vcount;
const irq = &bus.io.irq;
if (should_handle) {
const event = self.queue.remove();
@@ -38,19 +41,36 @@ pub const Scheduler = struct {
},
.HBlank => {
// The End of a Hblank (During Draw or Vblank)
const old_scanline = bus.ppu.vcount.scanline.read();
const old_scanline = vcount.scanline.read();
const scanline = (old_scanline + 1) % 228;
bus.ppu.vcount.scanline.write(scanline);
bus.ppu.dispstat.hblank.unset();
vcount.scanline.write(scanline);
stat.hblank.unset();
// Perform Vc == VcT check
const coincidence = scanline == stat.vcount_trigger.read();
stat.coincidence.write(coincidence);
if (coincidence and stat.vcount_irq.read()) {
irq.coincidence.set();
cpu.handleInterrupt();
}
if (scanline < 160) {
// Transitioning to another Draw
self.push(.Draw, self.tick + (240 * 4));
} else {
// Transitioning to a Vblank
if (scanline < 227) bus.ppu.dispstat.vblank.set() else bus.ppu.dispstat.vblank.unset();
if (scanline == 160) {
stat.vblank.set();
if (stat.vblank_irq.read()) {
irq.vblank.set();
cpu.handleInterrupt();
}
}
if (scanline == 227) stat.vblank.unset();
self.push(.VBlank, self.tick + (240 * 4));
}
},
@@ -59,11 +79,24 @@ pub const Scheduler = struct {
bus.ppu.drawScanline();
// Transitioning to a Hblank
if (bus.ppu.dispstat.hblank_irq.read()) {
bus.io.irq.hblank.set();
cpu.handleInterrupt();
}
bus.ppu.dispstat.hblank.set();
self.push(.HBlank, self.tick + (68 * 4));
},
.VBlank => {
// The end of a Vblank
// Transitioning to a Hblank
if (bus.ppu.dispstat.hblank_irq.read()) {
bus.io.irq.hblank.set();
cpu.handleInterrupt();
}
bus.ppu.dispstat.hblank.set();
self.push(.HBlank, self.tick + (68 * 4));
},
}