@@ -137,6 +137,7 @@ cpu->gprs[ARM_SP] = DS7_SP_BASE;
 
 	struct DS* ds = (struct DS*) cpu->master;
 	DSMemoryReset(ds);
+	DS7IOInit(ds);
 
 	struct DSCartridge* header = ds->romVf->map(ds->romVf, sizeof(*header), MAP_READ);
 	if (header) {
@@ -166,6 +167,8 @@ ARMSetPrivilegeMode(cpu, MODE_SYSTEM);
 	cpu->gprs[ARM_SP] = DS9_SP_BASE;
 
 	struct DS* ds = (struct DS*) cpu->master;
+	DS9IOInit(ds);
+
 	struct DSCartridge* header = ds->romVf->map(ds->romVf, sizeof(*header), MAP_READ);
 	if (header) {
 		// TODO: Error check

@@ -0,0 +1,115 @@
+/* Copyright (c) 2013-2016 Jeffrey Pfau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "io.h"
+
+#include "ds/ds.h"
+
+mLOG_DEFINE_CATEGORY(DS_IO, "DS I/O");
+
+static void _writeIPCSync(struct ARMCore* remoteCpu, uint16_t* remoteIo, int16_t value) {
+	remoteIo[DS7_REG_IPCSYNC >> 1] &= 0xFFF0;
+	remoteIo[DS7_REG_IPCSYNC >> 1] |= (value >> 8) & 0x0F;
+	if (value & 0x2000 && remoteIo[DS7_REG_IPCSYNC >> 1] & 0x4000) {
+		mLOG(DS_IO, STUB, "Unimplemented IPC IRQ");
+		UNUSED(remoteCpu);
+	}
+}
+
+void DS7IOInit(struct DS* ds) {
+	memset(ds->memory.io7, 0, sizeof(ds->memory.io7));
+}
+
+void DS7IOWrite(struct DS* ds, uint32_t address, uint16_t value) {
+	switch (address) {
+	case DS9_REG_IPCSYNC:
+		value &= 0x6F00;
+		value |= ds->memory.io7[address >> 1] & 0x000F;
+		_writeIPCSync(ds->arm9, ds->memory.io9, value);
+		break;
+	default:
+		mLOG(DS_IO, STUB, "Stub DS7 I/O register write: %06X", address);
+		if (address >= DS7_REG_MAX) {
+			mLOG(DS_IO, GAME_ERROR, "Write to unused DS7 I/O register: %06X", address);
+			return;
+		}
+		break;
+	}
+	ds->memory.io7[address >> 1] = value;
+}
+
+void DS7IOWrite8(struct DS* ds, uint32_t address, uint8_t value) {
+	if (address < DS7_REG_MAX) {
+		uint16_t value16 = value << (8 * (address & 1));
+		value16 |= (ds->memory.io7[(address & 0xFFF) >> 1]) & ~(0xFF << (8 * (address & 1)));
+		DS7IOWrite(ds, address & 0xFFFFFFFE, value16);
+	} else {
+		mLOG(DS, STUB, "Writing to unknown DS7 register: %08X:%02X", address, value);
+	}
+}
+
+void DS7IOWrite32(struct DS* ds, uint32_t address, uint32_t value);
+
+uint16_t DS7IORead(struct DS* ds, uint32_t address) {
+	switch (address) {
+	case DS7_REG_IPCSYNC:
+		// Handled transparently by the registers
+		break;
+	default:
+		mLOG(DS_IO, STUB, "Stub DS7 I/O register read: %06X", address);
+	}
+	if (address < DS7_REG_MAX) {
+		return ds->memory.io7[address >> 1];
+	}
+	return 0;
+}
+
+void DS9IOInit(struct DS* ds) {
+	memset(ds->memory.io9, 0, sizeof(ds->memory.io9));
+}
+
+void DS9IOWrite(struct DS* ds, uint32_t address, uint16_t value) {
+	switch (address) {
+	case DS9_REG_IPCSYNC:
+		value &= 0x6F00;
+		value |= ds->memory.io9[address >> 1] & 0x000F;
+		_writeIPCSync(ds->arm7, ds->memory.io7, value);
+		break;
+	default:
+		mLOG(DS_IO, STUB, "Stub DS9 I/O register write: %06X", address);
+		if (address >= DS7_REG_MAX) {
+			mLOG(DS_IO, GAME_ERROR, "Write to unused DS9 I/O register: %06X", address);
+			return;
+		}
+		break;
+	}
+	ds->memory.io9[address >> 1] = value;
+}
+
+void DS9IOWrite8(struct DS* ds, uint32_t address, uint8_t value) {
+	if (address < DS9_REG_MAX) {
+		uint16_t value16 = value << (8 * (address & 1));
+		value16 |= (ds->memory.io9[(address & 0x1FFF) >> 1]) & ~(0xFF << (8 * (address & 1)));
+		DS9IOWrite(ds, address & 0xFFFFFFFE, value16);
+	} else {
+		mLOG(DS, STUB, "Writing to unknown DS9 register: %08X:%02X", address, value);
+	}
+}
+
+void DS9IOWrite32(struct DS* ds, uint32_t address, uint32_t value);
+
+uint16_t DS9IORead(struct DS* ds, uint32_t address) {
+	switch (address) {
+	case DS9_REG_IPCSYNC:
+		// Handled transparently by the registers
+		break;
+	default:
+		mLOG(DS_IO, STUB, "Stub DS9 I/O register read: %06X", address);
+	}
+	if (address < DS9_REG_MAX) {
+		return ds->memory.io9[address >> 1];
+	}
+	return 0;
+}

@@ -0,0 +1,342 @@
+/* Copyright (c) 2013-2016 Jeffrey Pfau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef DS_IO_H
+#define DS_IO_H
+
+#include "util/common.h"
+
+#include "core/log.h"
+
+enum DS7IORegisters {
+	// Video
+	DS7_REG_DISPSTAT = 0x004,
+	DS7_REG_VCOUNT = 0x006,
+
+	// DMA
+	DS7_REG_DISPSTAT_REG_DMA0SAD_LO = 0x0B0,
+	DS7_REG_DISPSTAT_REG_DMA0SAD_HI = 0x0B2,
+	DS7_REG_DISPSTAT_REG_DMA0DAD_LO = 0x0B4,
+	DS7_REG_DISPSTAT_REG_DMA0DAD_HI = 0x0B6,
+	DS7_REG_DISPSTAT_REG_DMA0CNT_LO = 0x0B8,
+	DS7_REG_DISPSTAT_REG_DMA0CNT_HI = 0x0BA,
+	DS7_REG_DISPSTAT_REG_DMA1SAD_LO = 0x0BC,
+	DS7_REG_DISPSTAT_REG_DMA1SAD_HI = 0x0BE,
+	DS7_REG_DISPSTAT_REG_DMA1DAD_LO = 0x0C0,
+	DS7_REG_DISPSTAT_REG_DMA1DAD_HI = 0x0C2,
+	DS7_REG_DISPSTAT_REG_DMA1CNT_LO = 0x0C4,
+	DS7_REG_DISPSTAT_REG_DMA1CNT_HI = 0x0C6,
+	DS7_REG_DISPSTAT_REG_DMA2SAD_LO = 0x0C8,
+	DS7_REG_DISPSTAT_REG_DMA2SAD_HI = 0x0CA,
+	DS7_REG_DISPSTAT_REG_DMA2DAD_LO = 0x0CC,
+	DS7_REG_DISPSTAT_REG_DMA2DAD_HI = 0x0CE,
+	DS7_REG_DISPSTAT_REG_DMA2CNT_LO = 0x0D0,
+	DS7_REG_DISPSTAT_REG_DMA2CNT_HI = 0x0D2,
+	DS7_REG_DISPSTAT_REG_DMA3SAD_LO = 0x0D4,
+	DS7_REG_DISPSTAT_REG_DMA3SAD_HI = 0x0D6,
+	DS7_REG_DISPSTAT_REG_DMA3DAD_LO = 0x0D8,
+	DS7_REG_DISPSTAT_REG_DMA3DAD_HI = 0x0DA,
+	DS7_REG_DISPSTAT_REG_DMA3CNT_LO = 0x0DC,
+	DS7_REG_DISPSTAT_REG_DMA3CNT_HI = 0x0DE,
+
+	// Timers
+	DS7_REG_TM0CNT_LO = 0x100,
+	DS7_REG_TM0CNT_HI = 0x102,
+	DS7_REG_TM1CNT_LO = 0x104,
+	DS7_REG_TM1CNT_HI = 0x106,
+	DS7_REG_TM2CNT_LO = 0x108,
+	DS7_REG_TM2CNT_HI = 0x10A,
+	DS7_REG_TM3CNT_LO = 0x10C,
+	DS7_REG_TM3CNT_HI = 0x10E,
+
+	// Keypad
+	DS7_REG_KEYINPUT = 0x130,
+	DS7_REG_KEYCNT = 0x132,
+	DS7_REG_EXTKEYIN = 0x136,
+	DS7_REG_RTC = 0x138,
+
+	// IPC
+	DS7_REG_IPCSYNC = 0x180,
+	DS7_REG_IPCFIFOCNT = 0x182,
+	DS7_REG_IPCFIFOSEND_LO = 0x184,
+	DS7_REG_IPCFIFOSEND_HI = 0x186,
+	DS7_REG_IPCFIFORECV_LO = 0x100000,
+	DS7_REG_IPCFIFORECV_HI = 0x100002,
+
+	// Game card
+	DS7_REG_AUXSPICNT = 0x1A0,
+	DS7_REG_AUXSPIDATA = 0x1A2,
+	DS7_REG_SLOT1CNT_LO = 0x1A4,
+	DS7_REG_SLOT1CNT_HI = 0x1A6,
+	DS7_REG_SLOT1CMD_0 = 0x1A8,
+	DS7_REG_SLOT1CMD_1 = 0x1A9,
+	DS7_REG_SLOT1CMD_2 = 0x1AA,
+	DS7_REG_SLOT1CMD_3 = 0x1AB,
+	DS7_REG_SLOT1CMD_4 = 0x1AC,
+	DS7_REG_SLOT1CMD_5 = 0x1AD,
+	DS7_REG_SLOT1CMD_6 = 0x1AE,
+	DS7_REG_SLOT1CMD_7 = 0x1AF,
+	DS7_REG_SLOT1DATA_0 = 0x100010,
+	DS7_REG_SLOT1DATA_1 = 0x100011,
+	DS7_REG_SLOT1DATA_2 = 0x100012,
+	DS7_REG_SLOT1DATA_3 = 0x100013,
+
+	// Interrupts, etc
+	DS7_REG_EXMEMSTAT = 0x204,
+	DS7_REG_IME = 0x208,
+	DS7_REG_IE_LO = 0x210,
+	DS7_REG_IE_HI = 0x212,
+	DS7_REG_IF_LO = 0x214,
+	DS7_REG_IF_HI = 0x216,
+
+	// Memory control
+	DS7_REG_VRAMSTAT = 0x240,
+	DS7_REG_WRAMSTAT = 0x241,
+	DS7_REG_POSTFLG = 0x300,
+	DS7_REG_HALTCNT = 0x301,
+	DS7_REG_POWCNT2 = 0x304,
+	DS7_REG_BIOSPROT_LO = 0x308,
+	DS7_REG_BIOSPROT_HI = 0x30A,
+
+	DS7_REG_MAX = 0x51E,
+};
+
+enum DS9IORegisters {
+	// Video
+	DS9_REG_A_DISPCNT_LO = 0x000,
+	DS9_REG_A_DISPCNT_HI = 0x002,
+	DS9_REG_DISPSTAT = 0x004,
+	DS9_REG_VCOUNT = 0x006,
+	DS9_REG_A_BG0CNT = 0x008,
+	DS9_REG_A_BG1CNT = 0x00A,
+	DS9_REG_A_BG2CNT = 0x00C,
+	DS9_REG_A_BG3CNT = 0x00E,
+	DS9_REG_A_BG0HOFS = 0x010,
+	DS9_REG_A_BG0VOFS = 0x012,
+	DS9_REG_A_BG1HOFS = 0x014,
+	DS9_REG_A_BG1VOFS = 0x016,
+	DS9_REG_A_BG2HOFS = 0x018,
+	DS9_REG_A_BG2VOFS = 0x01A,
+	DS9_REG_A_BG3HOFS = 0x01C,
+	DS9_REG_A_BG3VOFS = 0x01E,
+	DS9_REG_A_BG2PA = 0x020,
+	DS9_REG_A_BG2PB = 0x022,
+	DS9_REG_A_BG2PC = 0x024,
+	DS9_REG_A_BG2PD = 0x026,
+	DS9_REG_A_BG2X_LO = 0x028,
+	DS9_REG_A_BG2X_HI = 0x02A,
+	DS9_REG_A_BG2Y_LO = 0x02C,
+	DS9_REG_A_BG2Y_HI = 0x02E,
+	DS9_REG_A_BG3PA = 0x030,
+	DS9_REG_A_BG3PB = 0x032,
+	DS9_REG_A_BG3PC = 0x034,
+	DS9_REG_A_BG3PD = 0x036,
+	DS9_REG_A_BG3X_LO = 0x038,
+	DS9_REG_A_BG3X_HI = 0x03A,
+	DS9_REG_A_BG3Y_LO = 0x03C,
+	DS9_REG_A_BG3Y_HI = 0x03E,
+	DS9_REG_A_WIN0H = 0x040,
+	DS9_REG_A_WIN1H = 0x042,
+	DS9_REG_A_WIN0V = 0x044,
+	DS9_REG_A_WIN1V = 0x046,
+	DS9_REG_A_WININ = 0x048,
+	DS9_REG_A_WINOUT = 0x04A,
+	DS9_REG_A_MOSAIC = 0x04C,
+	DS9_REG_A_BLDCNT = 0x050,
+	DS9_REG_A_BLDALPHA = 0x052,
+	DS9_REG_A_BLDY = 0x054,
+	DS9_REG_DISP3DCNT = 0x060,
+	DS9_REG_DISPCAPCNT_LO = 0x064,
+	DS9_REG_DISPCAPCNT_HI = 0x066,
+	DS9_REG_DISP_MMEM_FIFO_LO = 0x068,
+	DS9_REG_DISP_MMEM_FIFO_HI = 0x06A,
+	DS9_REG_A_MASTER_BRIGHT = 0x06C,
+
+	DS9_REG_B_DISPCNT_LO = 0x1000,
+	DS9_REG_B_DISPCNT_HI = 0x1002,
+	DS9_REG_B_BG0CNT = 0x1008,
+	DS9_REG_B_BG1CNT = 0x100A,
+	DS9_REG_B_BG2CNT = 0x100C,
+	DS9_REG_B_BG3CNT = 0x100E,
+	DS9_REG_B_BG0HOFS = 0x1010,
+	DS9_REG_B_BG0VOFS = 0x1012,
+	DS9_REG_B_BG1HOFS = 0x1014,
+	DS9_REG_B_BG1VOFS = 0x1016,
+	DS9_REG_B_BG2HOFS = 0x1018,
+	DS9_REG_B_BG2VOFS = 0x101A,
+	DS9_REG_B_BG3HOFS = 0x101C,
+	DS9_REG_B_BG3VOFS = 0x101E,
+	DS9_REG_B_BG2PA = 0x1020,
+	DS9_REG_B_BG2PB = 0x1022,
+	DS9_REG_B_BG2PC = 0x1024,
+	DS9_REG_B_BG2PD = 0x1026,
+	DS9_REG_B_BG2X_LO = 0x1028,
+	DS9_REG_B_BG2X_HI = 0x102A,
+	DS9_REG_B_BG2Y_LO = 0x102C,
+	DS9_REG_B_BG2Y_HI = 0x102E,
+	DS9_REG_B_BG3PA = 0x1030,
+	DS9_REG_B_BG3PB = 0x1032,
+	DS9_REG_B_BG3PC = 0x1034,
+	DS9_REG_B_BG3PD = 0x1036,
+	DS9_REG_B_BG3X_LO = 0x1038,
+	DS9_REG_B_BG3X_HI = 0x103A,
+	DS9_REG_B_BG3Y_LO = 0x103C,
+	DS9_REG_B_BG3Y_HI = 0x103E,
+	DS9_REG_B_WIN0H = 0x1040,
+	DS9_REG_B_WIN1H = 0x1042,
+	DS9_REG_B_WIN0V = 0x1044,
+	DS9_REG_B_WIN1V = 0x1046,
+	DS9_REG_B_WININ = 0x1048,
+	DS9_REG_B_WINOUT = 0x104A,
+	DS9_REG_B_MOSAIC = 0x104C,
+	DS9_REG_B_BLDCNT = 0x1050,
+	DS9_REG_B_BLDALPHA = 0x1052,
+	DS9_REG_B_BLDY = 0x1054,
+	DS9_REG_B_MASTER_BRIGHT = 0x106C,
+
+	// DMA
+	DS9_REG_DMA0SAD_LO = 0x0B0,
+	DS9_REG_DMA0SAD_HI = 0x0B2,
+	DS9_REG_DMA0DAD_LO = 0x0B4,
+	DS9_REG_DMA0DAD_HI = 0x0B6,
+	DS9_REG_DMA0CNT_LO = 0x0B8,
+	DS9_REG_DMA0CNT_HI = 0x0BA,
+	DS9_REG_DMA1SAD_LO = 0x0BC,
+	DS9_REG_DMA1SAD_HI = 0x0BE,
+	DS9_REG_DMA1DAD_LO = 0x0C0,
+	DS9_REG_DMA1DAD_HI = 0x0C2,
+	DS9_REG_DMA1CNT_LO = 0x0C4,
+	DS9_REG_DMA1CNT_HI = 0x0C6,
+	DS9_REG_DMA2SAD_LO = 0x0C8,
+	DS9_REG_DMA2SAD_HI = 0x0CA,
+	DS9_REG_DMA2DAD_LO = 0x0CC,
+	DS9_REG_DMA2DAD_HI = 0x0CE,
+	DS9_REG_DMA2CNT_LO = 0x0D0,
+	DS9_REG_DMA2CNT_HI = 0x0D2,
+	DS9_REG_DMA3SAD_LO = 0x0D4,
+	DS9_REG_DMA3SAD_HI = 0x0D6,
+	DS9_REG_DMA3DAD_LO = 0x0D8,
+	DS9_REG_DMA3DAD_HI = 0x0DA,
+	DS9_REG_DMA3CNT_LO = 0x0DC,
+	DS9_REG_DMA3CNT_HI = 0x0DE,
+	DS9_REG_DMA0FILL_LO = 0x0E0,
+	DS9_REG_DMA0FILL_HI = 0x0E2,
+	DS9_REG_DMA1FILL_LO = 0x0E4,
+	DS9_REG_DMA1FILL_HI = 0x0E6,
+	DS9_REG_DMA2FILL_LO = 0x0E8,
+	DS9_REG_DMA2FILL_HI = 0x0EA,
+	DS9_REG_DMA3FILL_LO = 0x0EC,
+	DS9_REG_DMA3FILL_HI = 0x0EE,
+
+	// Timers
+	DS9_REG_TM0CNT_LO = 0x100,
+	DS9_REG_TM0CNT_HI = 0x102,
+	DS9_REG_TM1CNT_LO = 0x104,
+	DS9_REG_TM1CNT_HI = 0x106,
+	DS9_REG_TM2CNT_LO = 0x108,
+	DS9_REG_TM2CNT_HI = 0x10A,
+	DS9_REG_TM3CNT_LO = 0x10C,
+	DS9_REG_TM3CNT_HI = 0x10E,
+
+	// Keypad
+	DS9_REG_KEYINPUT = 0x130,
+	DS9_REG_KEYCNT = 0x132,
+
+	// IPC
+	DS9_REG_IPCSYNC = 0x180,
+	DS9_REG_IPCFIFOCNT = 0x182,
+	DS9_REG_IPCFIFOSEND_LO = 0x184,
+	DS9_REG_IPCFIFOSEND_HI = 0x186,
+	DS9_REG_IPCFIFORECV_LO = 0x100000,
+	DS9_REG_IPCFIFORECV_HI = 0x100002,
+
+	// Game card
+	DS9_REG_AUXSPICNT = 0x1A0,
+	DS9_REG_AUXSPIDATA = 0x1A2,
+	DS9_REG_SLOT1CNT_LO = 0x1A4,
+	DS9_REG_SLOT1CNT_HI = 0x1A6,
+	DS9_REG_SLOT1CMD_0 = 0x1A8,
+	DS9_REG_SLOT1CMD_1 = 0x1A9,
+	DS9_REG_SLOT1CMD_2 = 0x1AA,
+	DS9_REG_SLOT1CMD_3 = 0x1AB,
+	DS9_REG_SLOT1CMD_4 = 0x1AC,
+	DS9_REG_SLOT1CMD_5 = 0x1AD,
+	DS9_REG_SLOT1CMD_6 = 0x1AE,
+	DS9_REG_SLOT1CMD_7 = 0x1AF,
+	DS9_REG_SLOT1DATA_0 = 0x100010,
+	DS9_REG_SLOT1DATA_1 = 0x100011,
+	DS9_REG_SLOT1DATA_2 = 0x100012,
+	DS9_REG_SLOT1DATA_3 = 0x100013,
+
+	// Interrupts, etc
+	DS9_REG_EXMEMCNT = 0x204,
+	DS9_REG_IME = 0x208,
+	DS9_REG_IE_LO = 0x210,
+	DS9_REG_IE_HI = 0x212,
+	DS9_REG_IF_LO = 0x214,
+	DS9_REG_IF_HI = 0x216,
+
+	// Memory control
+	DS9_REG_VRAMCNT_A = 0x240,
+	DS9_REG_VRAMCNT_B = 0x241,
+	DS9_REG_VRAMCNT_C = 0x242,
+	DS9_REG_VRAMCNT_D = 0x243,
+	DS9_REG_VRAMCNT_E = 0x244,
+	DS9_REG_VRAMCNT_F = 0x245,
+	DS9_REG_VRAMCNT_G = 0x246,
+	DS9_REG_WRAMCNT = 0x247,
+	DS9_REG_VRAMCNT_H = 0x248,
+	DS9_REG_VRAMCNT_I = 0x249,
+
+	// Math
+	DS9_REG_DIVCNT = 0x280,
+	DS9_REG_DIV_NUMER_0 = 0x290,
+	DS9_REG_DIV_NUMER_1 = 0x292,
+	DS9_REG_DIV_NUMER_2 = 0x294,
+	DS9_REG_DIV_NUMER_3 = 0x296,
+	DS9_REG_DIV_DENOM_0 = 0x298,
+	DS9_REG_DIV_DENOM_1 = 0x29A,
+	DS9_REG_DIV_DENOM_2 = 0x29C,
+	DS9_REG_DIV_DENOM_3 = 0x29E,
+	DS9_REG_DIV_RESULT_0 = 0x2A0,
+	DS9_REG_DIV_RESULT_1 = 0x2A2,
+	DS9_REG_DIV_RESULT_2 = 0x2A4,
+	DS9_REG_DIV_RESULT_3 = 0x2A6,
+	DS9_REG_DIVREM_RESULT_0 = 0x2A8,
+	DS9_REG_DIVREM_RESULT_1 = 0x2AA,
+	DS9_REG_DIVREM_RESULT_2 = 0x2AC,
+	DS9_REG_DIVREM_RESULT_3 = 0x2AE,
+	DS9_REG_SQRTCNT = 0x2B0,
+	DS9_REG_SQRT_RESULT_LO = 0x2B4,
+	DS9_REG_SQRT_RESULT_HI = 0x2B6,
+	DS9_REG_SQRT_PARAM_0 = 0x2B8,
+	DS9_REG_SQRT_PARAM_1 = 0x2BA,
+	DS9_REG_SQRT_PARAM_2 = 0x2BC,
+	DS9_REG_SQRT_PARAM_3 = 0x2BE,
+
+	DS9_REG_MAX = 0x106E,
+
+	DS9_REG_POSTFLG = 0x300,
+	DS9_REG_POWCNT1 = 0x304,
+};
+
+mLOG_DECLARE_CATEGORY(DS_IO);
+
+extern const char* const DS7IORegisterNames[];
+extern const char* const DS9IORegisterNames[];
+
+struct DS;
+void DS7IOInit(struct DS* ds);
+void DS7IOWrite(struct DS* ds, uint32_t address, uint16_t value);
+void DS7IOWrite8(struct DS* ds, uint32_t address, uint8_t value);
+void DS7IOWrite32(struct DS* ds, uint32_t address, uint32_t value);
+uint16_t DS7IORead(struct DS* ds, uint32_t address);
+
+void DS9IOInit(struct DS* ds);
+void DS9IOWrite(struct DS* ds, uint32_t address, uint16_t value);
+void DS9IOWrite8(struct DS* ds, uint32_t address, uint8_t value);
+void DS9IOWrite32(struct DS* ds, uint32_t address, uint32_t value);
+uint16_t DS9IORead(struct DS* ds, uint32_t address);
+#endif

@@ -8,6 +8,7 @@
 #include "arm/macros.h"
 
 #include "ds/ds.h"
+#include "ds/io.h"
 #include "util/math.h"
 #include "util/memory.h"
 
@@ -284,6 +285,9 @@ LOAD_16(value, address & (DS_SIZE_RAM - 1), memory->ram);
 			break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Load16: %08X", address);
+	case DS_REGION_IO:
+		value = DS7IORead(ds, address & 0x00FFFFFF);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Load16: %08X", address);
 		break;
@@ -374,6 +378,9 @@ break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Store16: %08X:%04X", address, value);
 		break;
+	case DS_REGION_IO:
+		DS7IOWrite(ds, address & 0x00FFFFFF, value);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Store16: %08X:%04X", address, value);
 		break;
@@ -397,6 +404,9 @@ ((uint8_t*) memory->ram)[address & (DS_SIZE_RAM - 1)] = value;
 			break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Store8: %08X:%02X", address, value);
+	case DS_REGION_IO:
+		DS7IOWrite8(ds, address & 0x00FFFFFF, value);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS7 Store8: %08X:%02X", address, value);
 		break;
@@ -609,6 +619,9 @@ LOAD_16(value, address & (DS_SIZE_RAM - 1), memory->ram);
 			break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Load16: %08X", address);
+	case DS_REGION_IO:
+		value = DS9IORead(ds, address & 0x00FFFFFF);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Load16: %08X", address);
 		break;
@@ -701,6 +714,9 @@ break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Store16: %08X:%04X", address, value);
 		break;
+	case DS_REGION_IO:
+		DS9IOWrite(ds, address & 0x00FFFFFF, value);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Store16: %08X:%04X", address, value);
 		break;
@@ -732,6 +748,9 @@ ((uint8_t*) memory->ram)[address & (DS_SIZE_RAM - 1)] = value;
 			break;
 		}
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Store8: %08X:%02X", address, value);
+	case DS_REGION_IO:
+		DS9IOWrite8(ds, address & 0x00FFFFFF, value);
+		break;
 	default:
 		mLOG(DS_MEM, STUB, "Unimplemented DS9 Store8: %08X:%02X", address, value);
 		break;

@@ -10,6 +10,7 @@ #include "util/common.h"
 
 #include "arm/arm.h"
 #include "core/log.h"
+#include "ds/io.h"
 
 enum DSMemoryRegion {
 	DS7_REGION_BIOS = 0x0,
@@ -114,6 +115,8 @@ uint32_t* ram;
 	uint32_t* wram;
 	uint32_t* wram7;
 	uint32_t* rom;
+	uint16_t io7[DS7_REG_MAX >> 1];
+	uint16_t io9[DS9_REG_MAX >> 1];
 
 	size_t romSize;
 	size_t wramSize7;