diff --git a/src/devices/cpu/upd7810/upd7810.cpp b/src/devices/cpu/upd7810/upd7810.cpp
index 72f7bf1a847..4f78ad642a0 100644
--- a/src/devices/cpu/upd7810/upd7810.cpp
+++ b/src/devices/cpu/upd7810/upd7810.cpp
@@ -505,24 +505,49 @@ offs_t upd78c05_device::disasm_disassemble(std::ostream &stream, offs_t pc, cons
 	return CPU_DISASSEMBLE_NAME(upd78c05)(this, stream, pc, oprom, opram, options);
 }
 
+WRITE8_MEMBER(upd7810_device::pa_w)
+{
+	COMBINE_DATA(&m_pa_in);
+}
+
+WRITE8_MEMBER(upd7810_device::pb_w)
+{
+	COMBINE_DATA(&m_pb_in);
+}
+
+WRITE8_MEMBER(upd7810_device::pc_w)
+{
+	COMBINE_DATA(&m_pc_in);
+}
+
+WRITE8_MEMBER(upd7810_device::pd_w)
+{
+	COMBINE_DATA(&m_pd_in);
+}
+
+WRITE8_MEMBER(upd7810_device::pf_w)
+{
+	COMBINE_DATA(&m_pf_in);
+}
+
 uint8_t upd7810_device::RP(offs_t port)
 {
 	uint8_t data = 0xff;
 	switch (port)
 	{
 	case UPD7810_PORTA:
-		if (m_ma)   // NS20031301 no need to read if the port is set as output
-			m_pa_in = m_pa_in_cb();
+		if (m_ma && !m_pa_in_cb.isnull())   // NS20031301 no need to read if the port is set as output
+			m_pa_in = m_pa_in_cb(0, m_ma);
 		data = (m_pa_in & m_ma) | (m_pa_out & ~m_ma);
 		break;
 	case UPD7810_PORTB:
-		if (m_mb)   // NS20031301 no need to read if the port is set as output
-			m_pb_in = m_pb_in_cb();
+		if (m_mb && !m_pb_in_cb.isnull())   // NS20031301 no need to read if the port is set as output
+			m_pb_in = m_pb_in_cb(0, m_mb);
 		data = (m_pb_in & m_mb) | (m_pb_out & ~m_mb);
 		break;
 	case UPD7810_PORTC:
-		if (m_mc)   // NS20031301 no need to read if the port is set as output
-			m_pc_in = m_pc_in_cb();
+		if (m_mc && !m_pc_in_cb.isnull())   // NS20031301 no need to read if the port is set as output
+			m_pc_in = m_pc_in_cb(0, m_mc);
 		data = (m_pc_in & m_mc) | (m_pc_out & ~m_mc);
 		if (m_mcc & 0x01)   /* PC0 = TxD output */
 			data = (data & ~0x01) | (m_txd & 1 ? 0x01 : 0x00);
@@ -542,7 +567,8 @@ uint8_t upd7810_device::RP(offs_t port)
 			data = (data & ~0x80) | (m_co1 & 1 ? 0x80 : 0x00);
 		break;
 	case UPD7810_PORTD:
-		m_pd_in = m_pd_in_cb();
+		if (!m_pd_in_cb.isnull())
+			m_pd_in = m_pd_in_cb();
 		switch (m_mm & 0x07)
 		{
 		case 0x00:          /* PD input mode, PF port mode */
@@ -557,7 +583,8 @@ uint8_t upd7810_device::RP(offs_t port)
 		}
 		break;
 	case UPD7810_PORTF:
-		m_pf_in = m_pf_in_cb();
+		if (m_mf && !m_pf_in_cb.isnull())
+			m_pf_in = m_pf_in_cb(0, m_mf);
 		switch (m_mm & 0x06)
 		{
 		case 0x00:          /* PD input/output mode, PF port mode */
@@ -1522,11 +1549,11 @@ void upd7810_device::base_device_start()
 	m_an6_func.resolve_safe(0);
 	m_an7_func.resolve_safe(0);
 
-	m_pa_in_cb.resolve_safe(0);
-	m_pb_in_cb.resolve_safe(0);
-	m_pc_in_cb.resolve_safe(0);
-	m_pd_in_cb.resolve_safe(0);
-	m_pf_in_cb.resolve_safe(0);
+	m_pa_in_cb.resolve();
+	m_pb_in_cb.resolve();
+	m_pc_in_cb.resolve();
+	m_pd_in_cb.resolve();
+	m_pf_in_cb.resolve();
 
 	m_pa_out_cb.resolve_safe();
 	m_pb_out_cb.resolve_safe();
diff --git a/src/devices/cpu/upd7810/upd7810.h b/src/devices/cpu/upd7810/upd7810.h
index fa20f0d781d..bc119260c0b 100644
--- a/src/devices/cpu/upd7810/upd7810.h
+++ b/src/devices/cpu/upd7810/upd7810.h
@@ -159,6 +159,12 @@ public:
 
 	template<class _Object> static devcb_base &set_pt_in_cb(device_t &device, _Object object) { return downcast<upd7810_device &>(device).m_pt_in_cb.set_callback(object); }
 
+	DECLARE_WRITE8_MEMBER(pa_w);
+	DECLARE_WRITE8_MEMBER(pb_w);
+	DECLARE_WRITE8_MEMBER(pc_w);
+	DECLARE_WRITE8_MEMBER(pd_w);
+	DECLARE_WRITE8_MEMBER(pf_w);
+
 protected:
 	// flags
 	enum