diff --git a/src/emu/machine/at45dbxx.c b/src/emu/machine/at45dbxx.c
index 27d4ca3b72a..869c9fec50d 100644
--- a/src/emu/machine/at45dbxx.c
+++ b/src/emu/machine/at45dbxx.c
@@ -45,14 +45,16 @@ const device_type AT45DB161 = &device_creator<at45db161_device>;
 
 at45db041_device::at45db041_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
 	: device_t(mconfig, AT45DB041, "AT45DB041", tag, owner, clock, "at45db041", __FILE__),
-	device_nvram_interface(mconfig, *this)
+	device_nvram_interface(mconfig, *this),
+	write_so(*this)
 {
 }
 
 
 at45db041_device::at45db041_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock, const char *shortname, const char *source)
 	: device_t(mconfig, type, name, tag, owner, clock, shortname, source),
-	device_nvram_interface(mconfig, *this)
+	device_nvram_interface(mconfig, *this),
+	write_so(*this)
 {
 }
 
@@ -90,6 +92,8 @@ void at45db041_device::device_start()
 	save_item(NAME(m_pin.wp));
 	save_item(NAME(m_pin.reset));
 	save_item(NAME(m_pin.busy));
+
+	write_so.resolve_safe();
 }
 
 
@@ -369,6 +373,7 @@ WRITE_LINE_MEMBER(at45db041_device::sck_w)
 		}
 		// output (part 2)
 		m_pin.so = (m_so_byte >> m_so_bits) & 1;
+		write_so(m_pin.so);
 		m_so_bits++;
 	}
 	// save sck
diff --git a/src/emu/machine/at45dbxx.h b/src/emu/machine/at45dbxx.h
index c90487f6e62..6091a36359f 100644
--- a/src/emu/machine/at45dbxx.h
+++ b/src/emu/machine/at45dbxx.h
@@ -29,6 +29,9 @@
 #define MCFG_AT45DB161_ADD(_tag) \
 	MCFG_DEVICE_ADD(_tag, AT45DB161, 0)
 
+#define MCFG_AT45DBXXX_SO_CALLBACK(_cb) \
+	devcb = &at45db041_device::set_so_cb(*device, DEVCB2_##_cb);
+
 
 // ======================> at45db041_device
 
@@ -46,6 +49,9 @@ public:
 
 	UINT8 *get_ptr() {  return m_data;  }
 
+	template<class _Object> static devcb2_base &set_so_cb(device_t &device, _Object object) { return downcast<at45db041_device &>(device).write_so.set_callback(object); }
+	devcb2_write_line write_so;
+
 protected:
 	// device-level overrides
 	virtual void device_start();
diff --git a/src/mess/drivers/cybiko.c b/src/mess/drivers/cybiko.c
index ee7e8acdd6d..2657ad47de6 100644
--- a/src/mess/drivers/cybiko.c
+++ b/src/mess/drivers/cybiko.c
@@ -94,21 +94,9 @@ static ADDRESS_MAP_START( cybikoxt_mem, AS_PROGRAM, 16, cybiko_state )
 	AM_RANGE( 0xe00000, 0xefffff ) AM_READ( cybikoxt_key_r )
 ADDRESS_MAP_END
 
-READ16_MEMBER(cybiko_state::serflash_r)
-{
-	if (m_flash1->so_r())
-	{
-		return 0x08;
-	}
-
-	return 0;
-}
-
 WRITE16_MEMBER(cybiko_state::serflash_w)
 {
 	m_flash1->cs_w ((data & 0x10) ? 0 : 1);
-	m_flash1->si_w ((data & 0x02) ? 1 : 0);
-	m_flash1->sck_w((data & 0x20) ? 1 : 0);
 }
 
 READ16_MEMBER(cybiko_state::clock_r)
@@ -155,11 +143,11 @@ READ16_MEMBER(cybiko_state::xtpower_r)
 //////////////////////
 
 static ADDRESS_MAP_START( cybikov1_io, AS_IO, 16, cybiko_state )
-	AM_RANGE(h8_device::PORT_3, h8_device::PORT_3) AM_READWRITE(serflash_r, serflash_w)
+	AM_RANGE(h8_device::PORT_3, h8_device::PORT_3) AM_WRITE(serflash_w)
 ADDRESS_MAP_END
 
 static ADDRESS_MAP_START( cybikov2_io, AS_IO, 16, cybiko_state )
-	AM_RANGE(h8_device::PORT_3, h8_device::PORT_3) AM_READWRITE(serflash_r, serflash_w)
+	AM_RANGE(h8_device::PORT_3, h8_device::PORT_3) AM_WRITE(serflash_w)
 	AM_RANGE(h8_device::PORT_F, h8_device::PORT_F) AM_READWRITE(clock_r, clock_w)
 ADDRESS_MAP_END
 
@@ -347,6 +335,10 @@ static MACHINE_CONFIG_START( cybikov1, cybiko_state )
 	MCFG_CPU_PROGRAM_MAP( cybikov1_mem )
 	MCFG_CPU_IO_MAP( cybikov1_io )
 
+	MCFG_DEVICE_MODIFY("maincpu:sci1")
+	MCFG_H8_SCI_TX_CALLBACK(DEVWRITELINE("^flash1", at45db041_device, si_w))
+	MCFG_H8_SCI_CLK_CALLBACK(DEVWRITELINE("^flash1", at45db041_device, sck_w))
+
 	// screen
 	MCFG_SCREEN_ADD("screen", RASTER)
 	MCFG_SCREEN_REFRESH_RATE( 60 )
@@ -365,6 +357,7 @@ static MACHINE_CONFIG_START( cybikov1, cybiko_state )
 	/* rtc */
 	MCFG_PCF8593_ADD("rtc")
 	MCFG_AT45DB041_ADD("flash1")
+	MCFG_AT45DBXXX_SO_CALLBACK(DEVWRITELINE("maincpu:sci1", h8_sci_device, rx_w))
 
 	MCFG_NVRAM_ADD_0FILL("nvram")
 	
@@ -380,8 +373,12 @@ MACHINE_CONFIG_END
 static MACHINE_CONFIG_DERIVED( cybikov2, cybikov1)
 	// cpu
 	MCFG_CPU_REPLACE("maincpu", H8S2246, XTAL_11_0592MHz)
-	MCFG_CPU_PROGRAM_MAP(cybikov2_mem )
-	MCFG_CPU_IO_MAP(cybikov2_io )
+	MCFG_CPU_PROGRAM_MAP(cybikov2_mem)
+	MCFG_CPU_IO_MAP(cybikov2_io)
+
+	MCFG_DEVICE_MODIFY("maincpu:sci1")
+	MCFG_H8_SCI_TX_CALLBACK(DEVWRITELINE("^flash1", at45db041_device, si_w))
+	MCFG_H8_SCI_CLK_CALLBACK(DEVWRITELINE("^flash1", at45db041_device, sck_w))
 
 	// machine
 	MCFG_SST_39VF020_ADD("flash2")