New NOT WORKING machine

=======================
BT Merlin M2105  [Nigel Barnes]

scripts/src/bus.lua

@@ -570,6 +570,8 @@ if (BUSES["ECONET"]~=null) then
 		MAME_DIR .. "src/devices/bus/econet/econet.h",
 		MAME_DIR .. "src/devices/bus/econet/e01.cpp",
 		MAME_DIR .. "src/devices/bus/econet/e01.h",
+		MAME_DIR .. "src/devices/bus/econet/ebridge.cpp",
+		MAME_DIR .. "src/devices/bus/econet/ebridge.h",
 	}
 end
 
@@ -583,6 +585,8 @@ if (BUSES["ELECTRON"]~=null) then
 	files {
 		MAME_DIR .. "src/devices/bus/electron/exp.cpp",
 		MAME_DIR .. "src/devices/bus/electron/exp.h",
+		MAME_DIR .. "src/devices/bus/electron/m2105.cpp",
+		MAME_DIR .. "src/devices/bus/electron/m2105.h",
 	}
 end
 

src/devices/bus/electron/exp.cpp

@@ -32,7 +32,7 @@ device_electron_expansion_interface::device_electron_expansion_interface(const m
 
 
 //-------------------------------------------------
-//  ~device_electron_expansion_card_interface - destructor
+//  ~device_electron_expansion_interface - destructor
 //-------------------------------------------------
 
 device_electron_expansion_interface::~device_electron_expansion_interface()
@@ -49,8 +49,22 @@ device_electron_expansion_interface::~device_electron_expansion_interface()
 //-------------------------------------------------
 
 electron_expansion_slot_device::electron_expansion_slot_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) :
-		device_t(mconfig, ELECTRON_EXPANSION_SLOT, "Expansion port", tag, owner, clock, "electron_expansion_slot", __FILE__),
+		device_t(mconfig, ELECTRON_EXPANSION_SLOT, "Acorn Electron Expansion port", tag, owner, clock, "electron_expansion_slot", __FILE__),
-		device_slot_interface(mconfig, *this)
+		device_slot_interface(mconfig, *this),
+	m_io(nullptr),
+	m_card(nullptr),
+	m_irq_handler(*this),
+	m_nmi_handler(*this),
+	m_reset_handler(*this)
+{
+}
+
+
+//-------------------------------------------------
+//  expansion_slot_device - destructor
+//-------------------------------------------------
+
+electron_expansion_slot_device::~electron_expansion_slot_device()
 {
 }
 
@@ -61,10 +75,12 @@ electron_expansion_slot_device::electron_expansion_slot_device(const machine_con
 
 void electron_expansion_slot_device::device_start()
 {
-	m_card = dynamic_cast<device_electron_expansion_interface *>(get_card_device());
+	// resolve callbacks
+	m_irq_handler.resolve_safe();
+	m_nmi_handler.resolve_safe();
+	m_reset_handler.resolve_safe();
 }
 
-
 //-------------------------------------------------
 //  device_reset - device-specific reset
 //-------------------------------------------------
@@ -77,6 +93,15 @@ void electron_expansion_slot_device::device_reset()
 	}
 }
 
+//-------------------------------------------------
+//  set_io_space - set address space we are attached to
+//-------------------------------------------------
+
+void electron_expansion_slot_device::set_io_space(address_space *io)
+{
+	m_io = io;
+}
+
 
 //-------------------------------------------------
 //  SLOT_INTERFACE( electron_expansion_devices )
@@ -90,7 +115,7 @@ void electron_expansion_slot_device::device_reset()
 //#include "aplus5.h"
 //#include "slogger.h"
 //#include "fbjoy.h"
-//#include "m2105.h"
+#include "m2105.h"
 
 
 SLOT_INTERFACE_START( electron_expansion_devices )
@@ -100,5 +125,5 @@ SLOT_INTERFACE_START( electron_expansion_devices )
 	//SLOT_INTERFACE("aplus5", ELECTRON_APLUS5)
 	//SLOT_INTERFACE("slogger", ELECTRON_SLOGGER)
 	//SLOT_INTERFACE("fbjoy", ELECTRON_FBJOY)
-	//SLOT_INTERFACE("m2105", ELECTRON_M2105)
+	SLOT_INTERFACE("m2105", ELECTRON_M2105)
 SLOT_INTERFACE_END

src/devices/bus/electron/exp.h

@@ -14,7 +14,7 @@
          0V   8  7   0V
         +5V  10  9   +5V
       16MHz  12  11  SOUND O/P
-                PHI OUT  14  13  13 IN
+    PHI OUT  14  13  /13 IN
         NMI  16  15  RST
         R/W  18  17  IRQ
          D6  20  19  D7
@@ -106,8 +106,20 @@ AC RETURNS (pins 3,4) - adaptor. A total of 6W may be drawn from these lines as
 	MCFG_DEVICE_ADD(_tag, ELECTRON_EXPANSION_SLOT, 0) \
 	MCFG_DEVICE_SLOT_INTERFACE(_slot_intf, _def_slot, false)
 
-#define MCFG_ELECTRON_PASSTHRU_EXPANSION_SLOT_ADD() \
+#define MCFG_ELECTRON_PASSTHRU_EXPANSION_SLOT_ADD(_def_slot) \
-	MCFG_ELECTRON_EXPANSION_SLOT_ADD(ELECTRON_EXPANSION_SLOT_TAG, 0, electron_expansion_devices, nullptr)
+	MCFG_ELECTRON_EXPANSION_SLOT_ADD(ELECTRON_EXPANSION_SLOT_TAG, electron_expansion_devices, _def_slot) \
+	MCFG_ELECTRON_EXPANSION_SLOT_IRQ_HANDLER(DEVWRITELINE(DEVICE_SELF_OWNER, electron_expansion_slot_device, irq_w)) \
+	MCFG_ELECTRON_EXPANSION_SLOT_NMI_HANDLER(DEVWRITELINE(DEVICE_SELF_OWNER, electron_expansion_slot_device, nmi_w)) \
+	MCFG_ELECTRON_EXPANSION_SLOT_RES_HANDLER(DEVWRITELINE(DEVICE_SELF_OWNER, electron_expansion_slot_device, reset_w))
+
+#define MCFG_ELECTRON_EXPANSION_SLOT_IRQ_HANDLER(_devcb) \
+	devcb = &electron_expansion_slot_device::set_irq_handler(*device, DEVCB_##_devcb);
+
+#define MCFG_ELECTRON_EXPANSION_SLOT_NMI_HANDLER(_devcb) \
+	devcb = &electron_expansion_slot_device::set_nmi_handler(*device, DEVCB_##_devcb);
+
+#define MCFG_ELECTRON_EXPANSION_SLOT_RES_HANDLER(_devcb) \
+	devcb = &electron_expansion_slot_device::set_reset_handler(*device, DEVCB_##_devcb);
 
 
 //**************************************************************************
@@ -118,13 +130,30 @@ AC RETURNS (pins 3,4) - adaptor. A total of 6W may be drawn from these lines as
 
 class device_electron_expansion_interface;
 
-class electron_expansion_slot_device : public device_t,
+class electron_expansion_slot_device : public device_t, public device_slot_interface
-												public device_slot_interface
 {
 public:
 	// construction/destruction
 	electron_expansion_slot_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
-	virtual ~electron_expansion_slot_device() {}
+	virtual ~electron_expansion_slot_device();
+
+	void set_io_space(address_space *io);
+
+	// callbacks
+	template<class _Object> static devcb_base &set_irq_handler(device_t &device, _Object object)
+		{ return downcast<electron_expansion_slot_device &>(device).m_irq_handler.set_callback(object); }
+
+	template<class _Object> static devcb_base &set_nmi_handler(device_t &device, _Object object)
+		{ return downcast<electron_expansion_slot_device &>(device).m_nmi_handler.set_callback(object); }
+
+	template<class _Object> static devcb_base &set_reset_handler(device_t &device, _Object object)
+		{ return downcast<electron_expansion_slot_device &>(device).m_reset_handler.set_callback(object); }
+
+	DECLARE_WRITE_LINE_MEMBER( irq_w ) { m_irq_handler(state); }
+	DECLARE_WRITE_LINE_MEMBER( nmi_w ) { m_nmi_handler(state); }
+	DECLARE_WRITE_LINE_MEMBER( reset_w ) { m_reset_handler(state); }
+
+	address_space *m_io;
 
 protected:
 	// device-level overrides
@@ -132,10 +161,15 @@ protected:
 	virtual void device_reset() override;
 
 	device_electron_expansion_interface *m_card;
+
+private:
+	devcb_write_line m_irq_handler;
+	devcb_write_line m_nmi_handler;
+	devcb_write_line m_reset_handler;
 };
 
 
-// ======================> device_electron_expansion_card_interface
+// ======================> device_electron_expansion_interface
 
 class device_electron_expansion_interface : public device_slot_card_interface
 {

src/devices/bus/electron/m2105.cpp

@@ -0,0 +1,154 @@
+// license:BSD-3-Clause
+// copyright-holders:Nigel Barnes
+/**********************************************************************
+
+    BT Merlin M2105
+
+**********************************************************************/
+
+
+#include "m2105.h"
+
+
+//**************************************************************************
+//  DEVICE DEFINITIONS
+//**************************************************************************
+
+const device_type ELECTRON_M2105 = &device_creator<electron_m2105_device>;
+
+
+//-------------------------------------------------
+//  ROM( m2105 )
+//-------------------------------------------------
+
+ROM_START( m2105 )
+	ROM_REGION(0x40000, "exp_rom", 0)
+	ROM_DEFAULT_BIOS("350")
+	ROM_SYSTEM_BIOS(0, "350", "v3.50")
+	ROMX_LOAD("ic22-sm-35l-1.ic22", 0x30000, 0x4000, CRC(e8f8a639) SHA1(eb7fa1e884be9c072ae0c1e598507b802422127f), ROM_BIOS(1))
+	ROMX_LOAD("ic23-sm-35l-1.ic23", 0x34000, 0x4000, CRC(b1bb1d83) SHA1(07ca3a93744519b8d03bbf1c3c3537c0a0a3c6fe), ROM_BIOS(1))
+	ROMX_LOAD("sk01-pc-35l-1.ic24", 0x38000, 0x4000, CRC(54fd4c09) SHA1(9588296306581580ba223cf6bce4be61476f14c4), ROM_BIOS(1))
+	ROMX_LOAD("sk02-pc-35l-1.ic24", 0x3c000, 0x4000, CRC(c08de988) SHA1(86f2da5f8e9a5301ad40360e286f841f42e94a99), ROM_BIOS(1))
+	ROM_SYSTEM_BIOS(1, "340", "v3.40")
+	ROMX_LOAD("ic22-sm-34l-1.ic22", 0x30000, 0x4000, CRC(b514b15f) SHA1(a9c6c20b5a4f860b000511dde2f54497bcdd97b0), ROM_BIOS(2))
+	ROMX_LOAD("ic23-sm-34l-1.ic23", 0x34000, 0x4000, CRC(18875889) SHA1(d1a7dd87c4d99869a1961becec5e9d567d8fad53), ROM_BIOS(2))
+	ROMX_LOAD("sk01-pc-34l-1.ic24", 0x38000, 0x4000, CRC(a8796c9e) SHA1(29bc01b8f7617b252e4b243d13b1bbd3cd32cc3b), ROM_BIOS(2))
+	ROMX_LOAD("sk02-pc-34l-1.ic24", 0x3c000, 0x4000, CRC(fa74063c) SHA1(cdc31c606e69e7a6d221b7340a310d475d487fc9), ROM_BIOS(2))
+	ROM_SYSTEM_BIOS(2, "207", "v2.07")
+	ROMX_LOAD("ic22-sm-207l-1.ic22", 0x30000, 0x4000, CRC(0c431547) SHA1(13d2eab49b9c79f507b7dd8436d1e56cf43be412), ROM_BIOS(3))
+	ROMX_LOAD("ic23-sm-207l-1.ic23", 0x34000, 0x4000, CRC(15044d49) SHA1(e75fe4321579a9027527a0e256050d1444b3fe82), ROM_BIOS(3))
+	ROMX_LOAD("sk01-pc-207l-1.ic24", 0x38000, 0x4000, CRC(0850bcea) SHA1(270e7a31e69e1454cfb70ced23a50f5d97efe4d5), ROM_BIOS(3))
+	ROMX_LOAD("sk02-pc-207l-1.ic24", 0x3c000, 0x4000, CRC(d8b9143f) SHA1(4e132c7a6dae4caf7203139b51882706d508c449), ROM_BIOS(3))
+
+	ROM_REGION(0x8000, "vsm", 0) /* system speech PHROM */
+	ROM_LOAD("phroma.bin", 0x0000, 0x4000, CRC(98e1bf9e) SHA1(b369809275cb67dfd8a749265e91adb2d2558ae6))
+ROM_END
+
+
+//-------------------------------------------------
+//  ADDRESS_MAP( m2105 )
+//-------------------------------------------------
+
+//static ADDRESS_MAP_START( m2105_mem, AS_IO, 8, electron_m2105_device )
+//	AM_RANGE(0x30000, 0x3ffff) AM_MIRROR(0x4000) AM_ROM AM_REGION("m2105_rom", 0)
+//ADDRESS_MAP_END
+
+
+//-------------------------------------------------
+//  MACHINE_DRIVER( m2105 )
+//-------------------------------------------------
+
+static MACHINE_CONFIG_FRAGMENT( m2105 )
+	/* sound hardware */
+	MCFG_SPEAKER_STANDARD_MONO("mono")
+
+	/* system via */
+	MCFG_DEVICE_ADD("via6522_0", VIA6522, 1000000)
+	/*MCFG_VIA6522_READPA_HANDLER(READ8(electron_m2105_device, m2105_via_system_read_porta))
+	MCFG_VIA6522_READPB_HANDLER(READ8(electron_m2105_device, m2105_via_system_read_portb))
+	MCFG_VIA6522_WRITEPA_HANDLER(WRITE8(electron_m2105_device, m2105_via_system_write_porta))
+	MCFG_VIA6522_WRITEPB_HANDLER(WRITE8(electron_m2105_device, m2105_via_system_write_portb))
+	MCFG_VIA6522_IRQ_HANDLER(WRITELINE(electron_m2105_device, m2105_via_system_irq_w))*/
+
+	/* user via */
+	MCFG_DEVICE_ADD("via6522_1", VIA6522, 1000000)
+	//MCFG_VIA6522_READPB_HANDLER(READ8(electron_m2105_device, m2105_via_user_read_portb))
+	MCFG_VIA6522_WRITEPA_HANDLER(DEVWRITE8("cent_data_out", output_latch_device, write))
+	//MCFG_VIA6522_WRITEPB_HANDLER(WRITE8(electron_m2105_device, m2105_via_user_write_portb))
+	MCFG_VIA6522_CA2_HANDLER(DEVWRITELINE("centronics", centronics_device, write_strobe))
+	//MCFG_VIA6522_IRQ_HANDLER(WRITELINE(electron_m2105_device, m2105_via_user_irq_w))
+
+	/* speech hardware */
+	MCFG_DEVICE_ADD("vsm", SPEECHROM, 0)
+	MCFG_SOUND_ADD("tms5220", TMS5220, 640000)
+	MCFG_TMS52XX_SPEECHROM("vsm")
+	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
+
+	/* duart */
+	MCFG_MC68681_ADD("sc2681", XTAL_3_6864MHz)
+	//MCFG_MC68681_IRQ_CALLBACK(DEVWRITELINE("maincpu", i80186_cpu_device, int0_w))
+	//MCFG_MC68681_A_TX_CALLBACK(DEVWRITELINE("rs232_1", rs232_port_device, write_txd))
+	//MCFG_MC68681_B_TX_CALLBACK(DEVWRITELINE("rs232_2", rs232_port_device, write_txd))
+	//MCFG_MC68681_OUTPORT_CALLBACK(WRITE8(electron_m2105_device, sio_out_w))
+
+	//MCFG_RS232_PORT_ADD("rs232_1", default_rs232_devices, "terminal")
+	//MCFG_RS232_RXD_HANDLER(DEVWRITELINE("sc2681", mc68681_device, rx_a_w))
+	//MCFG_RS232_PORT_ADD("rs232_2", default_rs232_devices, nullptr)
+	//MCFG_RS232_RXD_HANDLER(DEVWRITELINE("sc2681", mc68681_device, rx_b_w))
+
+	/* printer */
+	MCFG_CENTRONICS_ADD("centronics", centronics_devices, "printer")
+	MCFG_CENTRONICS_ACK_HANDLER(DEVWRITELINE("via6522_1", via6522_device, write_ca1)) MCFG_DEVCB_INVERT /* ack seems to be inverted? */
+	MCFG_CENTRONICS_OUTPUT_LATCH_ADD("cent_data_out", "centronics")
+MACHINE_CONFIG_END
+
+
+//-------------------------------------------------
+//  machine_config_additions - device-specific
+//  machine configurations
+//-------------------------------------------------
+
+machine_config_constructor electron_m2105_device::device_mconfig_additions() const
+{
+	return MACHINE_CONFIG_NAME( m2105 );
+}
+
+const rom_entry *electron_m2105_device::device_rom_region() const
+{
+	return ROM_NAME( m2105 );
+}
+
+//**************************************************************************
+//  LIVE DEVICE
+//**************************************************************************
+
+//-------------------------------------------------
+//  electron_m2105_device - constructor
+//-------------------------------------------------
+
+electron_m2105_device::electron_m2105_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
+	: device_t(mconfig, ELECTRON_M2105, "BT Merlin M2105", tag, owner, clock, "electron_m2105", __FILE__),
+		device_electron_expansion_interface(mconfig, *this),
+		m_exp_rom(*this, "exp_rom"),
+		m_via6522_0(*this, "via6522_0"),
+		m_via6522_1(*this, "via6522_1"),
+		m_tms(*this, "tms5220"),
+		m_centronics(*this, "centronics")
+{
+}
+
+//-------------------------------------------------
+//  device_start - device-specific startup
+//-------------------------------------------------
+
+void electron_m2105_device::device_start()
+{
+}
+
+//-------------------------------------------------
+//  device_reset - device-specific reset
+//-------------------------------------------------
+
+void electron_m2105_device::device_reset()
+{
+}

src/devices/bus/electron/m2105.h

@@ -0,0 +1,55 @@
+// license:BSD-3-Clause
+// copyright-holders:Nigel Barnes
+/**********************************************************************
+
+    BT Merlin M2105
+
+**********************************************************************/
+
+
+#ifndef __ELECTRON_M2105__
+#define __ELECTRON_M2105__
+
+#include "emu.h"
+#include "exp.h"
+#include "machine/6522via.h"
+#include "machine/mc68681.h"
+#include "sound/tms5220.h"
+#include "bus/centronics/ctronics.h"
+#include "bus/rs232/rs232.h"
+
+//**************************************************************************
+//  TYPE DEFINITIONS
+//**************************************************************************
+
+class electron_m2105_device:
+	public device_t,
+	public device_electron_expansion_interface
+
+{
+public:
+	// construction/destruction
+	electron_m2105_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
+
+	// optional information overrides
+	virtual machine_config_constructor device_mconfig_additions() const override;
+	virtual const rom_entry *device_rom_region() const override;
+
+protected:
+	virtual void device_start() override;
+	virtual void device_reset() override;
+
+private:
+	required_memory_region m_exp_rom;
+	required_device<via6522_device> m_via6522_0;
+	required_device<via6522_device> m_via6522_1;
+	required_device<tms5220_device> m_tms;
+	required_device<centronics_device> m_centronics;
+};
+
+
+// device type definition
+extern const device_type ELECTRON_M2105;
+
+
+#endif /* __ELECTRON_M2105__ */

src/mame/drivers/electron.cpp

@@ -54,7 +54,6 @@ that can be done through BASIC programs seem to behave properly (most of the tim
 
 Incomplete:
     - Sound (sound is too high?)
-    - Graphics (seems to be wrong for several games)
     - 1 MHz bus is not emulated
     - Bus claiming by ULA is not implemented
     - Currently the cartridge support always loads the upper rom in page 12
@@ -223,8 +222,11 @@ static MACHINE_CONFIG_START( electron, electron_state )
 	MCFG_GENERIC_CARTSLOT_ADD("cartslot", generic_plain_slot, "electron_cart")
 	MCFG_GENERIC_LOAD(electron_state, electron_cart)
 
-	/* expansion ports */
+	/* expansion port */
 	MCFG_ELECTRON_EXPANSION_SLOT_ADD("exp", electron_expansion_devices, nullptr)
+	MCFG_ELECTRON_EXPANSION_SLOT_IRQ_HANDLER(INPUTLINE("maincpu", M6502_IRQ_LINE))
+	MCFG_ELECTRON_EXPANSION_SLOT_NMI_HANDLER(INPUTLINE("maincpu", M6502_NMI_LINE))
+	MCFG_ELECTRON_EXPANSION_SLOT_RES_HANDLER(INPUTLINE("maincpu", INPUT_LINE_RESET))
 
 	/* software lists */
 	MCFG_SOFTWARE_LIST_ADD("cass_list", "electron_cass")
@@ -232,31 +234,48 @@ static MACHINE_CONFIG_START( electron, electron_state )
 MACHINE_CONFIG_END
 
 
+static MACHINE_CONFIG_DERIVED( btm2105, electron )
+	MCFG_SCREEN_MODIFY("screen")
+	MCFG_SCREEN_COLOR(rgb_t::amber)
+
+	/* expansion port */
+	MCFG_DEVICE_MODIFY("exp")
+	MCFG_DEVICE_SLOT_INTERFACE(electron_expansion_devices, "m2105", true)
+
+	/* software lists */
+	MCFG_SOFTWARE_LIST_REMOVE("cass_list")
+MACHINE_CONFIG_END
+
+
 /* Electron Rom Load */
 ROM_START(electron)
 	ROM_REGION( 0x10000, "maincpu", ROMREGION_ERASEFF )
 	ROM_REGION( 0x44000, "user1", 0 ) /* OS Rom */
-	ROM_LOAD( "os.rom", 0x40000, 0x4000, CRC(bf63fb1f) SHA1(a48b8fa0cfb09140e808ac8a187316c605a0b32e) ) /* Os rom */
+	ROM_LOAD( "os.rom", 0x40000, 0x4000, CRC(bf63fb1f) SHA1(a48b8fa0cfb09140e808ac8a187316c605a0b32e) ) /* OS rom */
-	/* 00000  0 available for cartridges                     */
+	/* 00000  0 Second external socket on the expansion module (SK2) */
-	/* 04000  1 available for cartridges                     */
+	/* 04000  1 Second external socket on the expansion module (SK2) */
-	/* 08000  2 available for cartridges                     */
+	/* 08000  2 First external socket on the expansion module (SK1)  */
-	/* 0c000  3 available for cartridges                     */
+	/* 0c000  3 First external socket on the expansion module (SK1)  */
-	/* 10000  4 available for cartridges                     */
+	/* 10000  4 Disc                                                 */
-	/* 14000  5 available for cartridges                     */
+	/* 14000  5 USER applications                                    */
-	/* 18000  6 available for cartridges                     */
+	/* 18000  6 USER applications                                    */
-	/* 1c000  7 available for cartridges                     */
+	/* 1c000  7 Modem interface ROM                                  */
-	/* 20000  8 keyboard                                     */
+	/* 20000  8 Keyboard                                             */
-	/* 24000  9 keyboard mirror                              */
+	/* 24000  9 Keyboard mirror                                      */
-	/* 28000 10 Basic rom                                    */
+	/* 28000 10 BASIC rom                                            */
+	/* 2c000 11 BASIC rom mirror                                     */
+	/* 30000 12 Expansion module operating system                    */
+	/* 34000 13 High priority slot in expansion module               */
+	/* 38000 14 ECONET                                               */
+	/* 3c000 15 Reserved                                             */
 		ROM_LOAD("basic.rom", 0x28000, 0x4000, CRC(79434781) SHA1(4a7393f3a45ea309f744441c16723e2ef447a281))
-	/* 2c000 11 Basic rom mirror                             */
 		ROM_COPY("user1", 0x28000, 0x2c000, 0x4000)
-	/* 30000 12 available for cartridges with a language ROM */
-	/* 34000 13 available for cartridges with a language ROM */
-	/* 38000 14 available for cartridges with a language ROM */
-	/* 3c000 15 available for cartridges with a language ROM */
 ROM_END
 
-/*     YEAR  NAME         PARENT    COMPAT    MACHINE   INPUT     CLASS          INIT  COMPANY  FULLNAME */
+
+#define rom_btm2105 rom_electron
+
+
+/*     YEAR  NAME       PARENT    COMPAT  MACHINE   INPUT     CLASS          INIT  COMPANY                             FULLNAME           FLAGS */
 COMP ( 1983, electron,  0,        0,      electron, electron, driver_device, 0,    "Acorn",                            "Acorn Electron",  MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS )
-//COMP ( 1985, btm2501,     electron, 0,        electron, electron, driver_device, 0,    "British Telecom Business Systems", "Merlin M2501", MACHINE_NOT_WORKING )
+COMP ( 1985, btm2105,   electron, 0,      btm2105,  electron, driver_device, 0,    "British Telecom Business Systems", "BT Merlin M2105", MACHINE_NOT_WORKING )

src/mame/includes/electron.h

@@ -76,6 +76,7 @@ public:
 		m_beeper(*this, "beeper"),
 		m_cart(*this, "cartslot"),
 		m_keybd(*this, "LINE")
+		m_exp(*this, "exp")
 	{ }
 
 	ULA m_ula;
@@ -105,6 +106,7 @@ public:
 	required_device<beep_device> m_beeper;
 	required_device<generic_slot_device> m_cart;
 	required_ioport_array<14> m_keybd;
+	required_device<electron_expansion_slot_device> m_exp;
 	inline UINT8 read_vram( UINT16 addr );
 	inline void electron_plot_pixel(bitmap_ind16 &bitmap, int x, int y, UINT32 color);
 	void electron_interrupt_handler(int mode, int interrupt);

src/mame/machine/electron.cpp

@@ -367,9 +367,36 @@ void electron_state::machine_start()
 		lo_rom = memregion("user1")->base();
 
 	membank("bank2")->configure_entries(0, 1, lo_rom, 0x4000);
-	membank("bank2")->configure_entries(1, 11, memregion("user1")->base() + 0x04000, 0x4000);
+	membank("bank2")->configure_entries(1, 1, up_rom, 0x4000);
-	membank("bank2")->configure_entries(12, 1, up_rom, 0x4000);
+
-	membank("bank2")->configure_entries(13, 3, memregion("user1")->base() + 0x34000, 0x4000);
+	for (int page = 2; page < 16; page++)
+		membank("bank2")->configure_entries(page, 1, memregion("user1")->base() + page * 0x4000, 0x4000);
+
+	/* enumerate expansion ROMs */
+	electron_expansion_slot_device* exp_port = m_exp;
+
+	while (exp_port != nullptr)
+	{
+		device_t* temp;
+
+		temp = dynamic_cast<device_t*>(exp_port->get_card_device());
+		if (temp != nullptr)
+		{
+			for (int page = 4; page < 16; page++)
+			{
+				memory_region *temp_region = temp->memregion("exp_rom");
+				if (temp_region != nullptr && temp_region->base() != nullptr && temp_region->base()[page * 0x4000 + 0x06] != 0x00)
+				{
+					membank("bank2")->configure_entries(page, 1, temp_region->base() + page * 0x4000, 0x4000);
+				}
+				exp_port = temp->subdevice<electron_expansion_slot_device>("exp");
+			}
+		}
+		else
+		{
+			exp_port = nullptr;
+		}
+	}
 
 	m_ula.interrupt_status = 0x82;
 	m_ula.interrupt_control = 0x00;

src/mame/mame.lst

@@ -11741,6 +11741,7 @@ avenger                         // (c) 1975 Electra
 
 @source:electron.cpp
 electron                        // 1983 Acorn Electron
+btm2105                         // 1985 BT Merlin M2105
 
 @source:elekscmp.cpp
 elekscmp                        //