@@ -254,6 +254,7 @@ void ARMSetPrivilegeMode(struct ARMCore*, enum PrivilegeMode);
 void ARMRaiseIRQ(struct ARMCore*);
 void ARMRaiseSWI(struct ARMCore*);
 void ARMRaiseUndefined(struct ARMCore*);
+void ARMHalt(struct ARMCore*);
 
 void ARMv4Run(struct ARMCore* cpu);
 void ARMv4RunLoop(struct ARMCore* cpu);

@@ -223,6 +223,11 @@ cpu->cpsr.i = 1;
 	cpu->cycles += currentCycles;
 }
 
+void ARMHalt(struct ARMCore* cpu) {
+	cpu->nextEvent = cpu->cycles;
+	cpu->halted = 1;
+}
+
 #define ARM_IMPLEMENT(VERSION) \
 	static inline void ARM ## VERSION ## Step(struct ARMCore* cpu) { \
 		uint32_t opcode = cpu->prefetch[0]; \

@@ -508,6 +508,14 @@ mLOG(DS, STUB, "CP15 region configuration write: Region: %i, Insn: %i, Base: %08X, Size: %08X", crm, opcode2, base, size);
 }
 
 static void _writeCache(struct ARMCore* cpu, int crm, int opcode2, uint32_t value) {
+	switch (crm) {
+	case 0:
+		if (opcode2 == 4) {
+			ARMHalt(cpu);
+			return;
+		}
+		break;
+	}
 	mLOG(DS, STUB, "CP15 cache write: CRm: %i, Op2: %i, Value: 0x%08X", crm, opcode2, value);
 }
 

@@ -10,6 +10,23 @@ #include <mgba/internal/ds/ipc.h>
 
 mLOG_DEFINE_CATEGORY(DS_IO, "DS I/O");
 
+static void _DSHaltCNT(struct DSCommon* dscore, uint8_t value) {
+	switch (value >> 6) {
+	case 0:
+	default:
+		break;
+	case 1:
+		mLOG(DS_IO, STUB, "Enter GBA mode not supported");
+		break;
+	case 2:
+		ARMHalt(dscore->cpu);
+		break;
+	case 3:
+		mLOG(DS_IO, STUB, "Enter sleep mode not supported");
+		break;
+	}
+}
+
 static uint32_t DSIOWrite(struct DSCommon* dscore, uint32_t address, uint16_t value) {
 	switch (address) {
 	// Timers
@@ -108,6 +125,10 @@ ds->memory.io7[address >> 1] = value;
 }
 
 void DS7IOWrite8(struct DS* ds, uint32_t address, uint8_t value) {
+	if (address == DS7_REG_HALTCNT) {
+		_DSHaltCNT(&ds->ds7, value);
+		return;
+	}
 	if (address < DS7_REG_MAX) {
 		uint16_t value16 = value << (8 * (address & 1));
 		value16 |= (ds->ds7.memory.io[(address & 0xFFF) >> 1]) & ~(0xFF << (8 * (address & 1)));

@@ -434,8 +434,7 @@ }
 }
 
 void GBAHalt(struct GBA* gba) {
-	gba->cpu->nextEvent = gba->cpu->cycles;
-	gba->cpu->halted = 1;
+	ARMHalt(gba->cpu);
 }
 
 void GBAStop(struct GBA* gba) {