diff --git a/src/devices/cpu/upd7810/upd7810.cpp b/src/devices/cpu/upd7810/upd7810.cpp
index ac123b07b46..467817c6086 100644
--- a/src/devices/cpu/upd7810/upd7810.cpp
+++ b/src/devices/cpu/upd7810/upd7810.cpp
@@ -736,7 +736,7 @@ void upd7810_device::upd7810_take_irq()
 	int irqline = 0;
 
 	/* global interrupt disable? */
-	if (0 == IFF)
+	if (0 == IFF && !(IRR & INTNMI))
 		return;
 
 	/* check the interrupts in priority sequence */
@@ -751,21 +751,22 @@ void upd7810_device::upd7810_take_irq()
 	if ((IRR & INTFT0)  && 0 == (MKL & 0x02))
 	{
 		vector = 0x0008;
-		if (!((IRR & INTFT1)    && 0 == (MKL & 0x04)))
-		IRR&=~INTFT0;
+		if (0 != (MKL & 0x04))
+			IRR&=~INTFT0;
 	}
 	else
 	if ((IRR & INTFT1)  && 0 == (MKL & 0x04))
 	{
 		vector = 0x0008;
-		IRR&=~INTFT1;
+		if (0 != (MKL & 0x02))
+			IRR&=~INTFT1;
 	}
 	else
 	if ((IRR & INTF1)   && 0 == (MKL & 0x08))
 	{
 		irqline = UPD7810_INTF1;
 		vector = 0x0010;
-		if (!((IRR & INTF2) && 0 == (MKL & 0x10)))
+		if (0 != (MKL & 0x10))
 			IRR&=~INTF1;
 	}
 	else
@@ -773,42 +774,50 @@ void upd7810_device::upd7810_take_irq()
 	{
 		irqline = UPD7810_INTF2;
 		vector = 0x0010;
-		IRR&=~INTF2;
+		if (0 != (MKL & 0x08))
+			IRR&=~INTF2;
 	}
 	else
 	if ((IRR & INTFE0)  && 0 == (MKL & 0x20))
 	{
 		vector = 0x0018;
-		if (!((IRR & INTFE1)    && 0 == (MKL & 0x40)))
-		IRR&=~INTFE0;
+		if (0 != (MKL & 0x40))
+			IRR&=~INTFE0;
 	}
 	else
 	if ((IRR & INTFE1)  && 0 == (MKL & 0x40))
 	{
 		vector = 0x0018;
-		IRR&=~INTFE1;
+		if (0 != (MKL & 0x20))
+			IRR&=~INTFE1;
 	}
 	else
 	if ((IRR & INTFEIN) && 0 == (MKL & 0x80))
 	{
 		vector = 0x0020;
+		if (0 != (MKH & 0x01))
+			IRR&=~INTFEIN;
 	}
 	else
 	if ((IRR & INTFAD)  && 0 == (MKH & 0x01))
 	{
 		vector = 0x0020;
+		if (0 != (MKL & 0x80))
+			IRR&=~INTFAD;
 	}
 	else
 	if ((IRR & INTFSR)  && 0 == (MKH & 0x02))
 	{
 		vector = 0x0028;
-		IRR&=~INTFSR;
+		if (0 != (MKH & 0x04))
+			IRR&=~INTFSR;
 	}
 	else
 	if ((IRR & INTFST)  && 0 == (MKH & 0x04))
 	{
 		vector = 0x0028;
-		IRR&=~INTFST;
+		if (0 != (MKH & 0x02))
+			IRR&=~INTFST;
 	}
 
 	if (vector)
@@ -822,7 +831,7 @@ void upd7810_device::upd7810_take_irq()
 		WM( SP, PCH );
 		SP--;
 		WM( SP, PCL );
-		IFF = 0;
+		IFF = m_iff_pending = 0;
 		PSW &= ~(SK|L0|L1);
 		PC = vector;
 	}
@@ -883,7 +892,7 @@ void upd7801_device::upd7810_take_irq()
 		WM( SP, PCH );
 		SP--;
 		WM( SP, PCL );
-		IFF = 0;
+		IFF = m_iff_pending = 0;
 		PSW &= ~(SK|L0|L1);
 		PC = vector;
 	}
@@ -1186,6 +1195,12 @@ void upd7810_device::upd7810_sio_input()
 	{
 		if (SML & 0x03)     /* asynchronous mode ? */
 		{
+			// start bit check
+			RXD = m_rxd_func();
+			m_rxs = (m_rxs >> 1) | ((uint16_t)RXD << 15);
+			if ((m_rxs & 0xc000) != 0x4000)
+				return;
+
 			switch (SML & 0xfc)
 			{
 			case 0x48:  /* 7bits, no parity, 1 stop bit */
@@ -1581,7 +1596,7 @@ void upd7810_device::base_device_start()
 	m_co0_func.resolve_safe();
 	m_co1_func.resolve_safe();
 	m_txd_func.resolve_safe();
-	m_rxd_func.resolve_safe(0);
+	m_rxd_func.resolve_safe(1);
 	m_an0_func.resolve_safe(0);
 	m_an1_func.resolve_safe(0);
 	m_an2_func.resolve_safe(0);
@@ -1614,6 +1629,7 @@ void upd7810_device::base_device_start()
 	save_item(NAME(m_op));
 	save_item(NAME(m_op2));
 	save_item(NAME(m_iff));
+	save_item(NAME(m_iff_pending));
 	save_item(NAME(m_ea.w.l));
 	save_item(NAME(m_va.w.l));
 	save_item(NAME(m_bc.w.l));
@@ -1800,6 +1816,7 @@ void upd7810_device::device_reset()
 	m_op = 0;
 	m_op2 = 0;
 	m_iff = 0;
+	m_iff_pending = 0;
 	m_psw = 0;
 	m_ea.d = 0;
 	m_va.d = 0;
@@ -1976,7 +1993,7 @@ void upd7810_device::execute_run()
 		}
 		m_icount -= cc;
 		upd7810_take_irq();
-
+		m_iff = m_iff_pending;
 	} while (m_icount > 0);
 }
 
diff --git a/src/devices/cpu/upd7810/upd7810.h b/src/devices/cpu/upd7810/upd7810.h
index 5905b931af1..adb0fe88a8e 100644
--- a/src/devices/cpu/upd7810/upd7810.h
+++ b/src/devices/cpu/upd7810/upd7810.h
@@ -239,6 +239,7 @@ protected:
 	uint8_t   m_op;     /* opcode */
 	uint8_t   m_op2;    /* opcode part 2 */
 	uint8_t   m_iff;    /* interrupt enable flip flop */
+	uint8_t   m_iff_pending;
 	uint8_t   m_psw;    /* processor status word */
 	PAIR    m_ea;     /* extended accumulator */
 	PAIR    m_va;     /* accumulator + vector register */