@@ -117,4 +117,7 @@ ThumbStep(cpu);
 	} else {
 		ARMStep(cpu);
 	}
+	if (cpu->cycles >= cpu->nextEvent) {
+		cpu->board->processEvents(cpu->board);
+	}
 }

@@ -87,7 +87,7 @@
 struct ARMBoard {
 	struct ARMCore* cpu;
 	void (*reset)(struct ARMBoard* board);
-	void (*nextEvent)(struct ARMBoard* board);
+	void (*processEvents)(struct ARMBoard* board);
 	void (*swi16)(struct ARMBoard* board, int immediate);
 	void (*swi32)(struct ARMBoard* board, int immediate);
 
@@ -99,8 +99,8 @@ int32_t gprs[16];
 	union PSR cpsr;
 	union PSR spsr;
 
-	uint32_t cycles;
-	uint32_t nextEvent;
+	int32_t cycles;
+	int32_t nextEvent;
 
 	int32_t bankedRegisters[6][7];
 	int32_t bankedSPSRs[6];

@@ -0,0 +1,27 @@
+#include "gba-video.h"
+
+#include <limits.h>
+
+void GBAVideoInit(struct GBAVideo* video) {
+	video->inHblank = 0;
+	video->inVblank = 0;
+	video->vcounter = 0;
+	video->vblankIRQ = 0;
+	video->hblankIRQ = 0;
+	video->vcounterIRQ = 0;
+	video->vcountSetting = 0;
+
+	video->vcount = -1;
+
+	video->lastHblank = 0;
+	video->nextHblank = VIDEO_HDRAW_LENGTH;
+	video->nextEvent = video->nextHblank;
+
+	video->nextHblankIRQ = 0;
+	video->nextVblankIRQ = 0;
+	video->nextVcounterIRQ = 0;
+}
+
+int32_t GBAVideoProcessEvents(struct GBAVideo* video, int32_t cycles) {
+	return INT_MAX;
+}

@@ -0,0 +1,61 @@
+#ifndef GBA_VIDEO_H
+#define GBA_VIDEO_H
+
+#include <stdint.h>
+
+enum {
+	VIDEO_CYCLES_PER_PIXEL = 4,
+
+	VIDEO_HORIZONTAL_PIXELS = 240,
+	VIDEO_HBLANK_PIXELS = 68,
+	VIDEO_HDRAW_LENGTH = 1006,
+	VIDEO_HBLANK_LENGTH = 226,
+	VIDEO_HORIZONTAL_LENGTH = 1232,
+
+	VIDEO_VERTICAL_PIXELS = 160,
+	VIDEO_VBLANK_PIXELS = 68,
+	VIDEO_VERTICAL_TOTAL_PIXELS = 228,
+
+	VIDEO_TOTAL_LENGTH = 280896,
+
+	REG_DISPSTAT_MASK = 0xFF38
+};
+
+struct GBAVideoRenderer {
+	void (*init)(struct GBAVideoRenderer* renderer);
+	void (*deinit)(struct GBAVideoRenderer* renderer);
+
+	uint16_t (*writeVideoRegister)(struct GBAVideoRenderer* renderer, uint32_t address, uint16_t value);
+	void (*drawScanline)(struct GBAVideoRenderer* video, int y);
+	void (*finishFrame)(struct GBAVideoRenderer* video);
+};
+
+struct GBAVideo {
+	struct GBAVideoRenderer renderer;
+
+	// DISPSTAT
+	int inHblank;
+	int inVblank;
+	int vcounter;
+	int blankIRQ;
+	int vblankIRQ;
+	int hblankIRQ;
+	int vcounterIRQ;
+	int vcountSetting;
+
+	// VCOUNT
+	int vcount;
+
+	int32_t lastHblank;
+	int32_t nextHblank;
+	int32_t nextEvent;
+
+	int32_t nextHblankIRQ;
+	int32_t nextVblankIRQ;
+	int32_t nextVcounterIRQ;
+};
+
+void GBAVideoInit(struct GBAVideo* video);
+int32_t GBAVideoProcessEvents(struct GBAVideo* video, int32_t cycles);
+
+#endif

@@ -4,6 +4,7 @@ #include "gba-bios.h"
 
 #include "debugger.h"
 
+#include <limits.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -15,6 +16,7 @@ SP_BASE_IRQ = 0x03FFFFA0,
 	SP_BASE_SUPERVISOR = 0x03FFFFE0
 };
 
+static void GBAProcessEvents(struct ARMBoard* board);
 static void GBAHitStub(struct ARMBoard* board, uint32_t opcode);
 
 void GBAInit(struct GBA* gba) {
@@ -40,6 +42,7 @@ }
 
 void GBABoardInit(struct GBABoard* board) {
 	board->d.reset = GBABoardReset;
+	board->d.processEvents = GBAProcessEvents;
 	board->d.swi16 = GBASwi16;
 	board->d.swi32 = GBASwi32;
 	board->d.hitStub = GBAHitStub;
@@ -53,6 +56,21 @@ ARMSetPrivilegeMode(cpu, MODE_SUPERVISOR);
 	cpu->gprs[ARM_SP] = SP_BASE_SUPERVISOR;
 	ARMSetPrivilegeMode(cpu, MODE_SYSTEM);
 	cpu->gprs[ARM_SP] = SP_BASE_SYSTEM;
+}
+
+static void GBAProcessEvents(struct ARMBoard* board) {
+	struct GBABoard* gbaBoard = (struct GBABoard*) board;
+	int32_t cycles = board->cpu->cycles;
+	int32_t nextEvent = INT_MAX;
+	int32_t testEvent;
+
+	testEvent = GBAVideoProcessEvents(&gbaBoard->p->video, cycles);
+	if (testEvent < nextEvent) {
+		nextEvent = testEvent;
+	}
+
+	board->cpu->cycles = 0;
+	board->cpu->nextEvent = nextEvent;
 }
 
 void GBAAttachDebugger(struct GBA* gba, struct ARMDebugger* debugger) {

@@ -4,6 +4,7 @@
 #include "arm.h"
 
 #include "gba-memory.h"
+#include "gba-video.h"
 
 enum GBAError {
 	GBA_NO_ERROR = 0,
@@ -23,6 +24,7 @@ struct GBA {
 	struct ARMCore cpu;
 	struct GBABoard board;
 	struct GBAMemory memory;
+	struct GBAVideo video;
 
 	struct ARMDebugger* debugger;