src/core/bus/GamePak.zig

@@ -316,7 +316,7 @@ const Gpio = struct {
 };
 
 /// GBA Real Time Clock
-const Clock = struct {
+pub const Clock = struct {
     const This = @This();
 
     writer: Writer,
@@ -501,11 +501,14 @@ const Clock = struct {
             .cpu = cpu,
             .gpio = gpio, // Can't use Arm7tdmi ptr b/c not initialized yet
         };
+
+        cpu.sched.push(.RealTimeClock, 1 << 24); // Every Second
     }
 
-    fn updateRealTime(self: *This) void {
-        const now = DateTime.now();
+    pub fn updateTime(self: *This) void {
+        self.cpu.sched.push(.RealTimeClock, 1 << 24); // Reschedule
 
+        const now = DateTime.now();
         self.year = toBcd(u8, @intCast(u8, now.date.year - 2000));
         self.month = toBcd(u5, now.date.month);
         self.day = toBcd(u3, now.date.day);

src/core/scheduler.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 
 const Bus = @import("Bus.zig");
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
+const Clock = @import("bus/GamePak.zig").Clock;
 
 const Order = std.math.Order;
 const PriorityQueue = std.PriorityQueue;
@@ -60,6 +61,13 @@ pub const Scheduler = struct {
                         3 => cpu.bus.apu.ch4.channelTimerOverflow(late),
                     }
                 },
+                .RealTimeClock => {
+                    const device = &cpu.bus.pak.gpio.device;
+                    if (device.kind != .Rtc or device.ptr == null) return;
+
+                    const clock = @ptrCast(*Clock, @alignCast(@alignOf(*Clock), device.ptr.?));
+                    clock.updateTime();
+                },
                 .FrameSequencer => cpu.bus.apu.tickFrameSequencer(late),
                 .SampleAudio => cpu.bus.apu.sampleAudio(late),
                 .HBlank => cpu.bus.ppu.handleHBlankEnd(cpu, late), // The end of a HBlank
@@ -118,4 +126,5 @@ pub const EventKind = union(enum) {
     SampleAudio,
     FrameSequencer,
     ApuChannel: u2,
+    RealTimeClock,
 };