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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
2022-02-20 18:40:22 -05:00
parent e5ab8b51a9
commit c2cf2d2965
3 changed files with 67 additions and 14 deletions
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36
src/cpu.zig
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@@ -246,14 +246,8 @@ pub const Arm7tdmi = struct {
}
pub fn step(self: *Self) u64 {
if (self.bus.io.is_halted) {
// const ie = self.bus.io.ie.raw;
// const irq = self.bus.io.irq.raw;
// if (ie & irq != 0) self.bus.io.is_halted = false;
// log.warn("FIXME: Enable GBA HALTing", .{});
}
// If we're halted, the cpu is disabled
if (self.bus.io.is_halted) return 1;
if (self.cpsr.t.read()) {
const opcode = self.thumbFetch();
@@ -272,6 +266,32 @@ pub const Arm7tdmi = struct {
return 1;
}
pub fn handleInterrupt(self: *Self) void {
const should_handle = self.bus.io.ie.raw & self.bus.io.irq.raw;
if (should_handle != 0) {
self.bus.io.is_halted = false;
// log.info("An Interrupt was Fired!", .{});
// Either IME is not true or I in CPSR is true
// Don't handle interrupts
if (!self.bus.io.ime or self.cpsr.i.read()) return;
// log.info("An interrupt was Handled!", .{});
// TODO: Should this behave like Software Interrupts?
const r15 = self.r[15] + if (self.cpsr.t.read()) @as(u32, 2) else 4;
const cpsr = self.cpsr.raw;
self.changeMode(.Irq);
self.cpsr.t.write(false);
self.cpsr.i.write(true);
self.r[14] = r15;
self.spsr.raw = cpsr;
self.r[15] = 0x000_0018;
}
}
fn thumbFetch(self: *Self) u16 {
const halfword = self.bus.read16(self.r[15]);
self.r[15] += 2;