diff --git a/src/mame/drivers/cdi.cpp b/src/mame/drivers/cdi.cpp
index 3c405ef3c15..524e28e2749 100644
--- a/src/mame/drivers/cdi.cpp
+++ b/src/mame/drivers/cdi.cpp
@@ -163,14 +163,14 @@ INPUT_CHANGED_MEMBER(cdi_state::mcu_input)
 
 static INPUT_PORTS_START( cdi )
 	PORT_START("MOUSEX")
-	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_X) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_X) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 
 	PORT_START("MOUSEY")
-	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_Y) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_Y) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 
 	PORT_START("MOUSEBTN")
-	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_BUTTON1) PORT_CODE(MOUSECODE_BUTTON1) PORT_NAME("Mouse Button 1") PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
-	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_BUTTON2) PORT_CODE(MOUSECODE_BUTTON2) PORT_NAME("Mouse Button 2") PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_BUTTON1) PORT_CODE(MOUSECODE_BUTTON1) PORT_NAME("Mouse Button 1") PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_BUTTON2) PORT_CODE(MOUSECODE_BUTTON2) PORT_NAME("Mouse Button 2") PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 	PORT_BIT(0xfc, IP_ACTIVE_HIGH, IPT_UNUSED)
 
 	PORT_START("DEBUG")
@@ -204,14 +204,14 @@ INPUT_PORTS_END
 
 static INPUT_PORTS_START( cdimono2 )
 	PORT_START("MOUSEX")
-	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_X) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) //PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_X) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) //PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 
 	PORT_START("MOUSEY")
-	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_Y) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) //PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x3ff, 0x000, IPT_MOUSE_Y) PORT_SENSITIVITY(100) PORT_MINMAX(0x000, 0x3ff) PORT_KEYDELTA(2) //PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 
 	PORT_START("MOUSEBTN")
-	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_BUTTON1) PORT_CODE(MOUSECODE_BUTTON1) PORT_NAME("Mouse Button 1") //PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
-	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_BUTTON2) PORT_CODE(MOUSECODE_BUTTON2) PORT_NAME("Mouse Button 2") //PORT_CHANGED_MEMBER("slave", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_BUTTON1) PORT_CODE(MOUSECODE_BUTTON1) PORT_NAME("Mouse Button 1") //PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
+	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_BUTTON2) PORT_CODE(MOUSECODE_BUTTON2) PORT_NAME("Mouse Button 2") //PORT_CHANGED_MEMBER("slave_hle", cdislave_device, mouse_update, 0)
 	PORT_BIT(0xfc, IP_ACTIVE_HIGH, IPT_UNUSED)
 
 	PORT_START("DEBUG")
@@ -276,6 +276,7 @@ MACHINE_RESET_MEMBER( cdi_state, cdimono1 )
 	UINT16 *dst   = m_planea;
 	memcpy(dst, src, 0x8);
 	memset(m_servo_io_regs, 0, 0x20);
+	memset(m_slave_io_regs, 0, 0x20);
 
 	m_maincpu->reset();
 
@@ -408,10 +409,11 @@ READ8_MEMBER( cdi_state::servo_io_r )
 			verboselog(*this, 1, "SERVO Port A Data read (%02x)\n", ret);
 			break;
 		case m68hc05eg_io_reg_t::PORT_B_DATA:
+			ret = 0x08;
 			verboselog(*this, 1, "SERVO Port B Data read (%02x)\n", ret);
-			ret |= 0x08;
 			break;
 		case m68hc05eg_io_reg_t::PORT_C_DATA:
+			ret |= INV_CADDYSWITCH_IN;
 			verboselog(*this, 1, "SERVO Port C Data read (%02x)\n", ret);
 			break;
 		case m68hc05eg_io_reg_t::PORT_D_INPUT:
@@ -511,13 +513,13 @@ WRITE8_MEMBER( cdi_state::servo_io_w )
 	{
 		case m68hc05eg_io_reg_t::PORT_A_DATA:
 			verboselog(*this, 1, "SERVO Port A Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_B_DATA:
 			verboselog(*this, 1, "SERVO Port B Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_C_DATA:
 			verboselog(*this, 1, "SERVO Port C Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_D_INPUT:
 			verboselog(*this, 1, "SERVO Port D Input write (%02x)\n", data);
 			return;
@@ -708,13 +710,13 @@ WRITE8_MEMBER( cdi_state::slave_io_w )
 	{
 		case m68hc05eg_io_reg_t::PORT_A_DATA:
 			verboselog(*this, 1, "SLAVE Port A Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_B_DATA:
 			verboselog(*this, 1, "SLAVE Port B Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_C_DATA:
 			verboselog(*this, 1, "SLAVE Port C Data write (%02x)\n", data);
-			break;
+			return;
 		case m68hc05eg_io_reg_t::PORT_D_INPUT:
 			verboselog(*this, 1, "SLAVE Port D Input write (%02x)\n", data);
 			return;
@@ -868,8 +870,6 @@ static MACHINE_CONFIG_START( cdimono2, cdi_state )
 	MCFG_MACHINE_RESET_OVERRIDE( cdi_state, cdimono2 )
 
 	MCFG_CDI68070_ADD("scc68070")
-	//MCFG_CDICDIC_ADD("cdic")
-	//MCFG_CDISLAVE_ADD("slave")
 	MCFG_CPU_ADD("servo", M68HC05EG, 2000000) /* Unknown clock speed, docs say 2MHz internal clock */
 	MCFG_CPU_PROGRAM_MAP(cdimono2_servo_mem)
 	MCFG_CPU_ADD("slave", M68HC05EG, 2000000) /* Unknown clock speed, docs say 2MHz internal clock */
diff --git a/src/mame/includes/cdi.h b/src/mame/includes/cdi.h
index 79cccbe1e90..2e7b13ada04 100644
--- a/src/mame/includes/cdi.h
+++ b/src/mame/includes/cdi.h
@@ -64,6 +64,13 @@ public:
 		ACOUNT_LO = 0x1b
 	};
 
+	enum servo_portc_bit_t
+	{
+		INV_JUC_OUT = (1 << 2),
+		INV_DIV4_IN = (1 << 5),
+		INV_CADDYSWITCH_IN = (1 << 7)
+	};
+
 	required_device<cpu_device> m_maincpu;
 	required_shared_ptr<UINT16> m_planea;
 	required_shared_ptr<UINT16> m_planeb;