diff --git a/src/mess/drivers/pmd85.c b/src/mess/drivers/pmd85.c
index 30ff756bc8c..b06f9b1ef72 100644
--- a/src/mess/drivers/pmd85.c
+++ b/src/mess/drivers/pmd85.c
@@ -542,6 +542,17 @@ static const cassette_interface pmd85_cassette_interface =
 	NULL
 };
 
+const i8251_interface pmd85_i8251_interface =
+{
+	DEVCB_DRIVER_LINE_MEMBER(pmd85_state, write_cas_tx),
+	DEVCB_NULL,
+	DEVCB_NULL,
+	DEVCB_NULL,
+	DEVCB_NULL,
+	DEVCB_NULL,
+	DEVCB_NULL
+};
+
 
 /* machine definition */
 static MACHINE_CONFIG_START( pmd85, pmd85_state )
@@ -574,8 +585,7 @@ static MACHINE_CONFIG_START( pmd85, pmd85_state )
 	MCFG_CASSETTE_ADD( "cassette", pmd85_cassette_interface )
 
 	/* uart */
-	MCFG_I8251_ADD("uart", default_i8251_interface)
-	MCFG_SERIAL_SOURCE_ADD("sercas")
+	MCFG_I8251_ADD("uart", pmd85_i8251_interface)
 
 	/* internal ram */
 	MCFG_RAM_ADD(RAM_TAG)
diff --git a/src/mess/includes/pmd85.h b/src/mess/includes/pmd85.h
index 34317536d94..8108a51e6d7 100644
--- a/src/mess/includes/pmd85.h
+++ b/src/mess/includes/pmd85.h
@@ -20,8 +20,7 @@ public:
 	enum
 	{
 		TIMER_CASSETTE,
-		TIMER_RESET,
-		TIMER_SETUP_MACHINE_STATE
+		TIMER_RESET
 	};
 
 	pmd85_state(const machine_config &mconfig, device_type type, const char *tag)
@@ -29,7 +28,6 @@ public:
 		m_maincpu(*this, "maincpu"),
 		m_ram(*this, RAM_TAG),
 		m_cassette(*this, "cassette"),
-		m_sercas(*this, "sercas"),
 		m_pit8253(*this, "pit8253"),
 		m_uart(*this, "uart"),
 		m_ppi8255_0(*this, "ppi8255_0"),
@@ -83,7 +81,7 @@ public:
 	UINT32 screen_update_pmd85(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect);
 	TIMER_CALLBACK_MEMBER(pmd85_cassette_timer_callback);
 	TIMER_CALLBACK_MEMBER(pmd_reset);
-	TIMER_CALLBACK_MEMBER(setup_machine_state);
+	DECLARE_WRITE_LINE_MEMBER(write_cas_tx);
 	DECLARE_READ8_MEMBER(pmd85_ppi_0_porta_r);
 	DECLARE_READ8_MEMBER(pmd85_ppi_0_portb_r);
 	DECLARE_READ8_MEMBER(pmd85_ppi_0_portc_r);
@@ -116,7 +114,6 @@ protected:
 	required_device<cpu_device> m_maincpu;
 	required_device<ram_device> m_ram;
 	required_device<cassette_image_device> m_cassette;
-	required_device<serial_source_device> m_sercas;
 	required_device<pit8253_device> m_pit8253;
 	optional_device<i8251_device> m_uart;
 	optional_device<i8255_device> m_ppi8255_0;
@@ -153,6 +150,8 @@ protected:
 	void pmd85_common_driver_init();
 	void pmd85_draw_scanline(bitmap_ind16 &bitmap, int pmd85_scanline);
 	virtual void device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr);
+
+	int m_cas_tx;
 };
 
 
diff --git a/src/mess/machine/pmd85.c b/src/mess/machine/pmd85.c
index 2f93a268ffc..205c252ba31 100644
--- a/src/mess/machine/pmd85.c
+++ b/src/mess/machine/pmd85.c
@@ -762,14 +762,15 @@ void pmd85_state::device_timer(emu_timer &timer, device_timer_id id, int param,
 	case TIMER_RESET:
 		pmd_reset(ptr, param);
 		break;
-	case TIMER_SETUP_MACHINE_STATE:
-		setup_machine_state(ptr, param);
-		break;
 	default:
 		assert_always(FALSE, "Unknown id in pmd85_state::device_timer");
 	}
 }
 
+WRITE_LINE_MEMBER(pmd85_state::write_cas_tx)
+{
+	m_cas_tx = state;
+}
 
 TIMER_CALLBACK_MEMBER(pmd85_state::pmd85_cassette_timer_callback)
 {
@@ -797,7 +798,7 @@ TIMER_CALLBACK_MEMBER(pmd85_state::pmd85_cassette_timer_callback)
 						{
 							data = (!m_previous_level && current_level) ? 1 : 0;
 
-							m_sercas->send_bit(data);
+							m_uart->write_rx(data);
 							m_uart->receive_clock();
 
 							m_clk_level_tape = 1;
@@ -817,7 +818,7 @@ TIMER_CALLBACK_MEMBER(pmd85_state::pmd85_cassette_timer_callback)
 		/* tape writing */
 		if (m_cassette->get_state()&CASSETTE_RECORD)
 		{
-			data = m_sercas->get_in_data_bit();
+			data = m_cas_tx;
 			data ^= m_clk_level_tape;
 			m_cassette->output(data&0x01 ? 1 : -1);
 
@@ -921,15 +922,6 @@ DRIVER_INIT_MEMBER(pmd85_state,c2717)
 	pmd85_common_driver_init();
 }
 
-TIMER_CALLBACK_MEMBER(pmd85_state::setup_machine_state)
-{
-	if (m_model != MATO)
-	{
-		m_uart->connect(m_sercas);
-	}
-}
-
-
 void pmd85_state::machine_reset()
 {
 	int i, j;
@@ -958,7 +950,5 @@ void pmd85_state::machine_reset()
 	m_startup_mem_map = 1;
 	(this->*update_memory)();
 
-	timer_set(attotime::zero, TIMER_SETUP_MACHINE_STATE);
-
 	m_maincpu->space(AS_PROGRAM).set_direct_update_handler(direct_update_delegate(FUNC(pmd85_state::pmd85_opbaseoverride), this));
 }