null modem hack

gistfile1.txt

diff --git a/src/devices/bus/rs232/null_modem.cpp b/src/devices/bus/rs232/null_modem.cpp
index 4c5d741..a859577 100644
--- a/src/devices/bus/rs232/null_modem.cpp
+++ b/src/devices/bus/rs232/null_modem.cpp
@@ -15,7 +15,8 @@ null_modem_device::null_modem_device(const machine_config &mconfig, const char *
 	m_rs232_stopbits(*this, "RS232_STOPBITS"),
 	m_input_count(0),
 	m_input_index(0),
-	m_timer_poll(nullptr)
+	m_timer_poll(nullptr),
+	m_rts(ASSERT_LINE)
 {
 }
 
@@ -68,6 +69,8 @@ WRITE_LINE_MEMBER(null_modem_device::update_serial)
 	output_dcd(0);
 	output_dsr(0);
 	output_cts(0);
+
+	m_rts = ASSERT_LINE;
 }
 
 void null_modem_device::device_reset()
@@ -91,6 +94,7 @@ void null_modem_device::device_timer(emu_timer &timer, device_timer_id id, int p
 
 void null_modem_device::queue()
 {
+	logerror("null: queue: empty %d rts %d\n", is_transmit_register_empty(), m_rts);
 	if (is_transmit_register_empty())
 	{
 		if (m_input_index == m_input_count)
@@ -99,7 +103,7 @@ void null_modem_device::queue()
 			m_input_count = m_stream->input(m_input_buffer, sizeof(m_input_buffer));
 		}
 
-		if (m_input_count != 0)
+		if (m_input_count != 0 && m_rts == ASSERT_LINE)
 		{
 			transmit_register_setup(m_input_buffer[m_input_index++]);
 
diff --git a/src/devices/bus/rs232/null_modem.h b/src/devices/bus/rs232/null_modem.h
index aed62fb..2015968 100644
--- a/src/devices/bus/rs232/null_modem.h
+++ b/src/devices/bus/rs232/null_modem.h
@@ -15,6 +15,8 @@ public:
 	virtual machine_config_constructor device_mconfig_additions() const override;
 
 	virtual WRITE_LINE_MEMBER( input_txd ) override { device_serial_interface::rx_w(state); }
+	virtual WRITE_LINE_MEMBER( input_rts ) override { logerror("null: rts %d <- %d\n", m_rts, state); m_rts = (line_state) state; }
+//	virtual WRITE_LINE_MEMBER( input_dtr ) override;
 
 	DECLARE_WRITE_LINE_MEMBER(update_serial);
 
@@ -46,6 +48,7 @@ private:
 	UINT32 m_input_count;
 	UINT32 m_input_index;
 	emu_timer *m_timer_poll;
+	line_state m_rts;
 };
 
 extern const device_type NULL_MODEM;