diff --git a/hash/c64_cart.xml b/hash/c64_cart.xml
index bd149d2bb55..2bc71509304 100644
--- a/hash/c64_cart.xml
+++ b/hash/c64_cart.xml
@@ -84,10 +84,11 @@
 		</part>
 	</software>
 
-	<software name="tdos12" supported="no">
+	<software name="tdos12" supported="partial">
 		<description>Triton QD TDOS 1.2</description>
 		<year>198?</year>
 		<publisher>Radofin</publisher>
+		<info name="usage" value="Enter 'SYS 32768' to run" />
 
 		<part name="cart" interface="c64_cart">
 			<feature name="slot" value="tdos" />
diff --git a/src/mess/machine/c64/tdos.c b/src/mess/machine/c64/tdos.c
index 852b8b5bb25..5797e313694 100644
--- a/src/mess/machine/c64/tdos.c
+++ b/src/mess/machine/c64/tdos.c
@@ -43,13 +43,27 @@
     |==========================================|
 
     ROM    - Hitachi HN482764G 8Kx8 EPROM "TDOS 1.2"
-    ULA    - Ferranti ULA5RB073E1 XZ-2085-1 custom (?)
+    ULA    - Ferranti ULA5RB073E1 XZ-2085-1 40-pin custom ULA
     SSDA   - Motorola MC68A52P SSDA
     CN1    - C64 expansion connector (pass-thru)
     CN2,3  - 19x1 flat ribbon cable to other PCB
     CN4    - 9 wires to 3" drive
     SW1    - cartridge on/off switch
 
+
+	Drive cable pinout
+	------------------
+    1    WP
+    2    WD
+    3    WG
+    4    MO
+    5    RD
+    6    RY
+    7    MS
+    8    RS
+    9    +5V
+    10   GND
+
 */
 
 #include "tdos.h"
@@ -82,8 +96,8 @@ static MC6852_INTERFACE( ssda_intf )
 	DEVCB_NULL,
 	DEVCB_NULL,
 	DEVCB_NULL,
-	DEVCB_NULL,
-	DEVCB_NULL,
+	DEVCB_LINE_GND,
+	DEVCB_LINE_GND,
 	DEVCB_NULL,
 	DEVCB_NULL
 };
@@ -111,6 +125,28 @@ machine_config_constructor c64_tdos_cartridge_device::device_mconfig_additions()
 }
 
 
+//-------------------------------------------------
+//  INPUT_PORTS( c64_tdos )
+//-------------------------------------------------
+
+static INPUT_PORTS_START( c64_tdos )
+	PORT_START("SW1")
+	PORT_DIPNAME( 0x01, 0x01, "Enabled" )
+	PORT_DIPSETTING(    0x00, DEF_STR( Off ) )
+	PORT_DIPSETTING(    0x01, DEF_STR( On ) )
+INPUT_PORTS_END
+
+
+//-------------------------------------------------
+//  input_ports - device-specific input ports
+//-------------------------------------------------
+
+ioport_constructor c64_tdos_cartridge_device::device_input_ports() const
+{
+	return INPUT_PORTS_NAME( c64_tdos );
+}
+
+
 
 //**************************************************************************
 //  LIVE DEVICE
@@ -124,7 +160,8 @@ c64_tdos_cartridge_device::c64_tdos_cartridge_device(const machine_config &mconf
 	device_t(mconfig, C64_TDOS, "C64 TDOS cartridge", tag, owner, clock, "c64_tdos", __FILE__),
 	device_c64_expansion_card_interface(mconfig, *this),
 	m_ssda(*this, MC68A52P_TAG),
-	m_exp(*this, C64_EXPANSION_SLOT_TAG)
+	m_exp(*this, C64_EXPANSION_SLOT_TAG),
+	m_sw1(*this, "SW1")
 {
 }
 
@@ -144,6 +181,11 @@ void c64_tdos_cartridge_device::device_start()
 
 void c64_tdos_cartridge_device::device_reset()
 {
+	m_ssda->reset();
+	//m_ula->reset();
+	//flip-flop reset
+
+	m_enabled = m_sw1->read();
 }
 
 
@@ -155,7 +197,40 @@ UINT8 c64_tdos_cartridge_device::c64_cd_r(address_space &space, offs_t offset, U
 {
 	data = m_exp->cd_r(space, offset, data, sphi2, ba, roml, romh, io1, io2);
 
-	// TODO
+	if (m_enabled && !roml)
+	{
+		data = m_roml[offset & 0x1fff];
+	}
+
+	if (m_enabled && !io2)
+	{
+		switch (offset >> 1)
+		{
+		case 0:
+			data = m_ssda->read(space, offset & 0x01);
+			break;
+
+		case 1:
+			break;
+
+		case 2:
+			/*
+			
+			    bit     description
+			
+			    0       
+			    1       
+			    2       
+			    3       
+			    4       
+			    5       drive MS
+			    6       drive WP
+			    7       drive RY
+			
+			*/
+			break;
+		}
+	}
 
 	return data;
 }
@@ -167,8 +242,37 @@ UINT8 c64_tdos_cartridge_device::c64_cd_r(address_space &space, offs_t offset, U
 
 void c64_tdos_cartridge_device::c64_cd_w(address_space &space, offs_t offset, UINT8 data, int sphi2, int ba, int roml, int romh, int io1, int io2)
 {
-	// TODO
 	m_exp->cd_w(space, offset, data, sphi2, ba, roml, romh, io1, io2);
+
+	if (m_enabled && !io2)
+	{
+		switch (offset >> 1)
+		{
+		case 0:
+			m_ssda->write(space, offset & 0x01, data);
+			break;
+
+		case 1:
+			/*
+			
+			    bit     description
+			
+			    0       
+			    1       
+			    2       
+			    3       
+			    4       
+			    5       ULA pin 8, inverted
+			    6       drive MO
+			    7       ULA pin 15
+			
+			*/
+			break;
+
+		case 2:
+			break;
+		}
+	}
 }
 
 
@@ -178,7 +282,7 @@ void c64_tdos_cartridge_device::c64_cd_w(address_space &space, offs_t offset, UI
 
 int c64_tdos_cartridge_device::c64_game_r(offs_t offset, int sphi2, int ba, int rw)
 {
-	return m_exp->game_r(offset, sphi2, ba, rw, m_slot->hiram());
+	return m_enabled ? 1 : m_exp->game_r(offset, sphi2, ba, rw, m_slot->hiram());
 }
 
 
@@ -188,5 +292,5 @@ int c64_tdos_cartridge_device::c64_game_r(offs_t offset, int sphi2, int ba, int
 
 int c64_tdos_cartridge_device::c64_exrom_r(offs_t offset, int sphi2, int ba, int rw)
 {
-	return m_exp->exrom_r(offset, sphi2, ba, rw, m_slot->hiram());
+	return m_enabled ? 0 : m_exp->exrom_r(offset, sphi2, ba, rw, m_slot->hiram());
 }
diff --git a/src/mess/machine/c64/tdos.h b/src/mess/machine/c64/tdos.h
index 711df0fcdc5..ddc7dfaba8b 100644
--- a/src/mess/machine/c64/tdos.h
+++ b/src/mess/machine/c64/tdos.h
@@ -33,6 +33,7 @@ public:
 
 	// optional information overrides
 	virtual machine_config_constructor device_mconfig_additions() const;
+	virtual ioport_constructor device_input_ports() const;
 
 protected:
 	// device-level overrides
@@ -48,6 +49,9 @@ protected:
 private:
 	required_device<mc6852_device> m_ssda;
 	required_device<c64_expansion_slot_device> m_exp;
+	required_ioport m_sw1;
+
+	bool m_enabled;
 };