diff --git a/scripts/src/bus.lua b/scripts/src/bus.lua
index 5c4273ea593..19bea082740 100644
--- a/scripts/src/bus.lua
+++ b/scripts/src/bus.lua
@@ -3928,16 +3928,18 @@ end
 
 if (BUSES["SG1000_EXP"]~=null) then
 	files {
-		MAME_DIR .. "src/devices/bus/sg1000_exp/sg1000exp.cpp",
-		MAME_DIR .. "src/devices/bus/sg1000_exp/sg1000exp.h",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/fm_unit.cpp",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/fm_unit.h",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/kblink.cpp",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/kblink.h",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/sg1000exp.cpp",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/sg1000exp.h",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/sk1100.cpp",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/sk1100.h",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/sk1100prn.cpp",
 		MAME_DIR .. "src/devices/bus/sg1000_exp/sk1100prn.h",
-		MAME_DIR .. "src/devices/bus/sg1000_exp/kblink.cpp",
-		MAME_DIR .. "src/devices/bus/sg1000_exp/kblink.h",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/sp400.cpp",
+		MAME_DIR .. "src/devices/bus/sg1000_exp/sp400.h",
 	}
 end
 
diff --git a/src/devices/bus/sg1000_exp/sk1100prn.cpp b/src/devices/bus/sg1000_exp/sk1100prn.cpp
index 2b24864d75b..24d5808c229 100644
--- a/src/devices/bus/sg1000_exp/sk1100prn.cpp
+++ b/src/devices/bus/sg1000_exp/sk1100prn.cpp
@@ -9,7 +9,7 @@
 #include "emu.h"
 #include "sk1100prn.h"
 // slot devices
-//#include "sp400.h"
+#include "sp400.h"
 #include "kblink.h"
 
 
@@ -120,6 +120,6 @@ int sk1100_printer_port_device::busy_r()
 
 void sk1100_printer_port_devices(device_slot_interface &device)
 {
-	//device.option_add("sp400", SP400_PRINTER); /* serial printer */
+	device.option_add("sp400", SP400_PRINTER); /* serial printer */
 	device.option_add("kblink", SK1100_LINK_CABLE);
 }
diff --git a/src/devices/bus/sg1000_exp/sp400.cpp b/src/devices/bus/sg1000_exp/sp400.cpp
new file mode 100644
index 00000000000..fce22cf7d51
--- /dev/null
+++ b/src/devices/bus/sg1000_exp/sp400.cpp
@@ -0,0 +1,233 @@
+// license: BSD-3-Clause
+// copyright-holders: Fabio Dalla Libera
+
+/*
+    Sega SP-400 Plotter
+
+    6805 dumped using https://github.com/charlesmacd/HD6805_Reader
+
+    Plotter uses ALPS Micrographic Printer DPG 1302 mechanism.
+
+    IC list:
+
+    * M5L8035LP (Mitsubishi clone of I8035)
+
+    P1 is the deserialized output data
+    P2.4 is the input serial data
+    P2.5 is busy (output to the computer)
+    P2.6 is the output strobe
+    P2.7 is busy (input from the 6805)
+
+    * HD6805V (Hitachi chip, pin compatible with MC6805P2, with 4K of ROM)
+
+    port A connected to the panel buttons
+        "By analyzing the disassembly I found out that three pins (PA5,6,7 of the 6805) are used to set
+        different configurations. The resolution can be changed, probably to support different mechanics.
+        The baud rate is 4800."
+    port B connected to the motors
+    port C connected to the pen and misc signals
+    port D connected to M5L8035LP parallel data
+*/
+
+// this is currently incomplete: missing paper output and pen sensor, everything else is working
+
+#include "emu.h"
+#include "sp400.h"
+
+#include "cpu/m6805/m68705.h"
+#include "cpu/mcs48/mcs48.h"
+
+
+namespace {
+
+class sp400_printer_device : public device_t, public device_sk1100_printer_port_interface
+{
+public:
+	static constexpr feature_type unemulated_features() { return feature::PRINTER; }
+
+	sp400_printer_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+	virtual void device_add_mconfig(machine_config &config) override ATTR_COLD;
+	virtual void device_start() override ATTR_COLD;
+
+	const tiny_rom_entry *device_rom_region() const override ATTR_COLD;
+	virtual ioport_constructor device_input_ports() const override ATTR_COLD;
+
+	virtual void input_data(int state) override { m_data = state; }
+	virtual int output_busy() override { return m_busy; }
+
+private:
+	void dser_map(address_map &map);
+	void dser_p1_w(uint8_t data);
+	uint8_t dser_p2_r();
+	void dser_p2_w(uint8_t data);
+
+	uint8_t mot_pa_r();
+	void mot_pb_w(uint8_t data);
+	uint8_t mot_pc_r();
+	void mot_pc_w(uint8_t data);
+	uint8_t mot_pd_r();
+	void update_pen_state(uint8_t data);
+	uint8_t pen_sensor() { return 0; }  // not currently hooked up
+
+	required_device<i8035_device> m_dsercpu;     // "deserializer CPU"
+	required_device<m6805_hmos_device> m_motcpu; // "motor CPU"
+
+	uint8_t m_data, m_busy;
+	uint8_t m_dserdataout, m_dserstrobe;
+	uint8_t m_motbusy, m_motpenup, m_motpendown;
+	uint8_t m_pendown;
+
+	required_ioport m_buttons;
+};
+
+sp400_printer_device::sp400_printer_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+	device_t(mconfig, SP400_PRINTER, tag, owner, clock),
+	device_sk1100_printer_port_interface(mconfig, *this),
+	m_dsercpu(*this, "dsercpu"),
+	m_motcpu(*this, "motcpu"),
+	m_data(0),
+	m_busy(1),
+	m_dserdataout(0xff),
+	m_dserstrobe(1),
+	m_motbusy(0),
+	m_motpenup(1),
+	m_motpendown(1),
+	m_pendown(0),
+	m_buttons(*this, "BUTTONS")
+{
+}
+
+void sp400_printer_device::device_start()
+{
+	save_item(NAME(m_data));
+	save_item(NAME(m_busy));
+	save_item(NAME(m_dserdataout));
+	save_item(NAME(m_dserstrobe));
+	save_item(NAME(m_motbusy));
+	save_item(NAME(m_motpenup));
+	save_item(NAME(m_motpendown));
+	save_item(NAME(m_pendown));
+}
+
+void sp400_printer_device::dser_map(address_map &map)
+{
+	map(0x0000, 0x0fff).rom();
+}
+
+void sp400_printer_device::dser_p1_w(uint8_t data)
+{
+	m_dserdataout = data;
+}
+
+void sp400_printer_device::dser_p2_w(uint8_t data)
+{
+	m_busy = BIT(data, 5);
+	m_dserstrobe = BIT(data, 6);
+	m_motcpu->set_input_line(M6805_IRQ_LINE, m_dserstrobe);
+}
+
+uint8_t sp400_printer_device::dser_p2_r()
+{
+	return
+			(m_motbusy << 7) |
+			(m_dserstrobe << 6) |
+			(m_busy << 5) |
+			(m_data << 4) |
+			(1 << 3) |
+			(1 << 2) |
+			(1 << 1) |
+			(1 << 0);
+}
+
+uint8_t sp400_printer_device::mot_pa_r()
+{
+	return
+			(0 << 0) |
+			(0 << 1) |
+			(m_buttons->read() << 2) |  // bits 2..4
+			(0 << 5) |
+			(0 << 6) |
+			(1 << 7);
+}
+
+void sp400_printer_device::mot_pb_w(uint8_t data)
+{
+	// cr stepper data in 0..3
+	// pf stepper data in 4..7
+}
+
+uint8_t sp400_printer_device::mot_pc_r()
+{
+	return
+			(m_motpenup   << 0) |
+			(m_motpendown << 1) |
+			(1 << 2) |
+			(pen_sensor() << 3) |
+			(m_motbusy    << 4) |
+			(1 << 5) | (1 << 6) | (1 << 7); // unconfirmed
+}
+
+void sp400_printer_device::mot_pc_w(uint8_t data)
+{
+	m_motpenup   = BIT(data, 0);
+	m_motpendown = BIT(data, 1);
+	m_motbusy    = BIT(data, 4);
+	update_pen_state(data);
+}
+
+uint8_t sp400_printer_device::mot_pd_r()
+{
+	return sp400_printer_device::m_dserdataout;
+}
+
+void sp400_printer_device::update_pen_state(uint8_t data)
+{
+	if (!BIT(data, 0)) m_pendown = 0;
+	if (!BIT(data, 1)) m_pendown = 1;
+}
+
+void sp400_printer_device::device_add_mconfig(machine_config &config)
+{
+	I8035(config, m_dsercpu, 4_MHz_XTAL);
+	m_dsercpu->p1_out_cb().set(FUNC(sp400_printer_device::dser_p1_w));
+	m_dsercpu->p2_in_cb().set(FUNC(sp400_printer_device::dser_p2_r));
+	m_dsercpu->p2_out_cb().set(FUNC(sp400_printer_device::dser_p2_w));
+	m_dsercpu->set_addrmap(AS_PROGRAM, &sp400_printer_device::dser_map);
+
+	M6805U3(config, m_motcpu, 4_MHz_XTAL);
+	m_motcpu->porta_r().set(FUNC(sp400_printer_device::mot_pa_r));
+	m_motcpu->portb_w().set(FUNC(sp400_printer_device::mot_pb_w));
+	m_motcpu->portc_r().set(FUNC(sp400_printer_device::mot_pc_r));
+	m_motcpu->portc_w().set(FUNC(sp400_printer_device::mot_pc_w));
+	m_motcpu->portd_r().set(FUNC(sp400_printer_device::mot_pd_r));
+}
+
+ROM_START( sp400 )
+	ROM_REGION( 0x1000, "dsercpu", 0 )
+	ROM_LOAD( "sp400_8035.bin", 0x0000, 0x1000, CRC(0eb48272) SHA1(08a2727f1592f5d2ecb2e368126ad7bfc5d3c270) )
+
+	ROM_REGION(0x1000, "motcpu", 0 )
+	ROM_LOAD( "sp400_hd6805v1.bin", 0x0000, 0x1000, CRC(aa073745) SHA1(65016f3b022af30cc6b084af1e43b29168721a60) )
+ROM_END
+
+const tiny_rom_entry *sp400_printer_device::device_rom_region() const
+{
+	return ROM_NAME( sp400 );
+}
+
+INPUT_PORTS_START( sp400 )
+	PORT_START("BUTTONS")
+	PORT_BIT(0x01, IP_ACTIVE_LOW, IPT_KEYPAD) PORT_NAME("Color Select") PORT_CODE(KEYCODE_2_PAD)
+	PORT_BIT(0x02, IP_ACTIVE_LOW, IPT_KEYPAD) PORT_NAME("Line Feed")    PORT_CODE(KEYCODE_1_PAD)
+	PORT_BIT(0x04, IP_ACTIVE_LOW, IPT_KEYPAD) PORT_NAME("Pen Change")   PORT_CODE(KEYCODE_3_PAD)
+INPUT_PORTS_END
+
+ioport_constructor sp400_printer_device::device_input_ports() const
+{
+	return INPUT_PORTS_NAME(sp400);
+}
+
+} // anonymous namespace
+
+DEFINE_DEVICE_TYPE_PRIVATE(SP400_PRINTER, device_sk1100_printer_port_interface, sp400_printer_device, "sega_sp400", "Sega SP-400 Plotter")
diff --git a/src/devices/bus/sg1000_exp/sp400.h b/src/devices/bus/sg1000_exp/sp400.h
new file mode 100644
index 00000000000..fa1d87c0878
--- /dev/null
+++ b/src/devices/bus/sg1000_exp/sp400.h
@@ -0,0 +1,13 @@
+// license: BSD-3-Clause
+// copyright-holders: Fabio Dalla Libera
+
+#ifndef MAME_BUS_SG1000_EXP_SP400_H
+#define MAME_BUS_SG1000_EXP_SP400_H
+
+#pragma once
+
+#include "sk1100prn.h"
+
+DECLARE_DEVICE_TYPE(SP400_PRINTER, device_sk1100_printer_port_interface)
+
+#endif // MAME_BUS_SG1000_EXP_SP400_H