summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/drivers/electron.cpp
blob: 4e0f88eef8dc2626787cf089dd983c999514f9a7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
// license:BSD-3-Clause
// copyright-holders:Wilbert Pol, Nigel Barnes
/******************************************************************************

Hardware Overview
-----------------
The Acorn Electron is a budget version of the BBC Micro home computer
Basic specs are:
6502 CPU @ 2MHz or 1MHz
32k RAM and 32k ROM
Text modes: 20x32, 40x25, 40x32, 80x25, 80x32
Graphics modes: 160x256 (4 or 16 colors), 320x256 (2 or 4 colors), 640x256 (2 colors), 320x200 (2 colors), 640x200 (2 colors)
Colors: 8 colors (either solid or flashing)
Sound: 1 channel, 7 octaves; built-in speaker
Internal ports for cassette storage, RGB/CVBS monitors and TV output
Various expansions can be added via the rear expansion port

PCB Layout
----------                           |-------------------|
                            |--------|  EXPANSION PORT   |
|-----|---------------------|                            |---||---------|
|MOD  | SPKR     16MHz                            LS169 18VAC||         []18VAC INPUT
|     |17.7345MHz               ROM                     18VAC|| POWER   |
|-----|       74S04                             |----|       || SUPPLY  |
|          KBD_CONN                    6502     |ULA |       ||         |
|CVBS                                           |----|       ||  +5VDC  |
|RGB                  LS00 LS86                              ||  -5VDC  |
|                                                         PWR||         |
|CASS         LM324   LS00 LS86 S74 LS74 4164 4164 4164 4164 ||         |
|------------------------------------------------------------||---------|
Notes: (all IC's shown. Only 16 ICs are used)
     6502 - 6502 CPU, clock input 2.000MHz [16/8]
      ULA - Custom logic chip 12CO21, also containing most of the BBC Micro circuitry
            Early PCB revisions used a PLCC68 chip in a socket. Later revisions used a
            PGA68 chip soldered directly into the motherboard
     4164 - 4164 64k x4-bit DRAM (4 chips for 32kbytes total)
      ROM - Hitachi HN613256 32k x8-bit mask ROM containing OS & BASIC
    LM324 - Texas Instruments LM324 Operational Amplifier
      MOD - UHF TV modulator UM1233-E36
     CVBS - Composite color video output socket
      RGB - RGB monitor video output socket
     CASS - Cassette port
      PWR - 3-pin power input from internal power supply
 KBD_CONN - 22-pin keyboard connector
     SPKR - 2-pin internal speaker connector


Master RAM Board
----------------
The Master RAM Board (MRB) is an internal expansion board from Slogger, and could
also be purchased pre-fitted in the form of the Electron 64.
The MRB comes with a new MOS which provides three modes of operation, selected by a
switch, which are Normal, Turbo, and 64K. The 64K mode was the first to provide a
'shadow mode' on the Electron.


Stop Press 64i
--------------
The Stop Press 64i (SP64i) is another internal expansion board from Slogger, which
also requires the MRB to fitted. Being released in the early 90's there are no known
working examples, but bare prototype boards and ROMs were discovered during a Slogger
workshop clearout.
It provides a re-written AMX Stop Press (Desktop Publishing) for the Electron to take
advantage of the extra memory provided by the Master RAM Board, and also offers
ROM/RAM sockets and User Port for a mouse.

******************************************************************************
Emulation notes:

I don't have a real system to verify the behaviour of the emulation. The things
that can be done through BASIC programs seem to behave properly (most of the time :).

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

Other internal boards to emulate:
    - Slogger Turbo Driver
    - Jafa Mode7 Mk2 Display Unit
    - move MRB and SP64i to an internal slot device?

******************************************************************************/

#include "emu.h"
#include "cpu/m6502/m6502.h"
#include "includes/electron.h"
#include "imagedev/cassette.h"
#include "formats/uef_cas.h"
#include "formats/csw_cas.h"
#include "sound/beep.h"
#include "screen.h"
#include "softlist.h"
#include "speaker.h"


void electron_state::electron_colours(palette_device &palette) const
{
	for (int i = 0; i < palette.entries(); i++)
	{
		palette.set_pen_color(i ^ 7, rgb_t(pal1bit(i >> 0), pal1bit(i >> 1), pal1bit(i >> 2)));
	}
}

void electron_state::electron_mem(address_map &map)
{
	map(0x0000, 0x7fff).rw(FUNC(electron_state::electron_mem_r), FUNC(electron_state::electron_mem_w));          /* 32KB of RAM */
	map(0x8000, 0xbfff).rw(FUNC(electron_state::electron_paged_r), FUNC(electron_state::electron_paged_w));      /* Banked ROM pages */
	map(0xc000, 0xffff).rw(FUNC(electron_state::electron_mos_r), FUNC(electron_state::electron_mos_w));          /* OS ROM */
	map(0xfc00, 0xfcff).rw(FUNC(electron_state::electron_fred_r), FUNC(electron_state::electron_fred_w));        /* FRED */
	map(0xfd00, 0xfdff).rw(FUNC(electron_state::electron_jim_r), FUNC(electron_state::electron_jim_w));          /* JIM */
	map(0xfe00, 0xfeff).rw(FUNC(electron_state::electron_sheila_r), FUNC(electron_state::electron_sheila_w));    /* SHEILA */
}

void electron_state::electron64_opcodes(address_map &map)
{
	map(0x0000, 0xffff).r(FUNC(electron_state::electron64_fetch_r));
}

INPUT_CHANGED_MEMBER(electron_state::trigger_reset)
{
	m_maincpu->set_input_line(INPUT_LINE_RESET, newval ? ASSERT_LINE : CLEAR_LINE);
	if (!newval)
	{
		m_exp->reset();
	}
}

static INPUT_PORTS_START( electron )
	PORT_START("LINE.0")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME(u8"\u2192 | \\") PORT_CODE(KEYCODE_BACKSLASH) PORT_CHAR(UCHAR_MAMEKEY(RIGHT)) PORT_CHAR('|') PORT_CHAR('\\') // on the real keyboard, this would be on the 1st row, the 3rd key after 0
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("COPY") PORT_CODE(KEYCODE_END)  PORT_CHAR(UCHAR_MAMEKEY(F1)) PORT_CHAR('[') PORT_CHAR(']')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_UNUSED)
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_SPACE)      PORT_CHAR(' ')

	PORT_START("LINE.1")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME(u8"\u2190 ^ ~") PORT_CODE(KEYCODE_EQUALS) PORT_CHAR(UCHAR_MAMEKEY(LEFT)) PORT_CHAR('^') PORT_CHAR('~')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME(u8"\u2193 _ }") PORT_CODE(KEYCODE_CLOSEBRACE) PORT_CHAR(UCHAR_MAMEKEY(DOWN)) PORT_CHAR('_') PORT_CHAR('}')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("RETURN") PORT_CODE(KEYCODE_ENTER)     PORT_CHAR(13)
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("DELETE") PORT_CODE(KEYCODE_BACKSPACE) PORT_CHAR(8)

	PORT_START("LINE.2")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_MINUS)      PORT_CHAR('-') PORT_CHAR('=')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME(u8"\u2191 £ {") PORT_CODE(KEYCODE_OPENBRACE) PORT_CHAR(UCHAR_MAMEKEY(UP)) PORT_CHAR(0xA3) PORT_CHAR('{')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_QUOTE)      PORT_CHAR(':') PORT_CHAR('*')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_UNUSED)

	PORT_START("LINE.3")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_0)          PORT_CHAR('0') PORT_CHAR('@')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_P)          PORT_CHAR('p') PORT_CHAR('P')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_COLON)      PORT_CHAR(';') PORT_CHAR('+')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_SLASH)      PORT_CHAR('/') PORT_CHAR('?')

	PORT_START("LINE.4")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_9)          PORT_CHAR('9') PORT_CHAR(')')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_O)          PORT_CHAR('o') PORT_CHAR('O')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_L)          PORT_CHAR('l') PORT_CHAR('L')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_STOP)       PORT_CHAR('.') PORT_CHAR('>')

	PORT_START("LINE.5")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_8)          PORT_CHAR('8') PORT_CHAR('(')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_I)          PORT_CHAR('i') PORT_CHAR('I')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_K)          PORT_CHAR('k') PORT_CHAR('K')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_COMMA)      PORT_CHAR(',') PORT_CHAR('<')

	PORT_START("LINE.6")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_7)          PORT_CHAR('7') PORT_CHAR('\'')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_U)          PORT_CHAR('u') PORT_CHAR('U')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_J)          PORT_CHAR('j') PORT_CHAR('J')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_M)          PORT_CHAR('m') PORT_CHAR('M')

	PORT_START("LINE.7")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_6)          PORT_CHAR('6') PORT_CHAR('&')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_Y)          PORT_CHAR('y') PORT_CHAR('Y')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_H)          PORT_CHAR('h') PORT_CHAR('H')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_N)          PORT_CHAR('n') PORT_CHAR('N')

	PORT_START("LINE.8")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_5)          PORT_CHAR('5') PORT_CHAR('%')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_T)          PORT_CHAR('t') PORT_CHAR('T')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_G)          PORT_CHAR('g') PORT_CHAR('G')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_B)          PORT_CHAR('b') PORT_CHAR('B')

	PORT_START("LINE.9")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_4)          PORT_CHAR('4') PORT_CHAR('$')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_R)          PORT_CHAR('r') PORT_CHAR('R')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_F)          PORT_CHAR('f') PORT_CHAR('F')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_V)          PORT_CHAR('v') PORT_CHAR('V')

	PORT_START("LINE.10")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_3)          PORT_CHAR('3') PORT_CHAR('#')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_E)          PORT_CHAR('e') PORT_CHAR('E')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_D)          PORT_CHAR('d') PORT_CHAR('D')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_C)          PORT_CHAR('c') PORT_CHAR('C')

	PORT_START("LINE.11")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_2)          PORT_CHAR('2') PORT_CHAR('"')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_W)          PORT_CHAR('w') PORT_CHAR('W')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_S)          PORT_CHAR('s') PORT_CHAR('S')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_X)          PORT_CHAR('x') PORT_CHAR('X')

	PORT_START("LINE.12")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_1)          PORT_CHAR('1') PORT_CHAR('!')
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_Q)          PORT_CHAR('q') PORT_CHAR('Q')
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_A)          PORT_CHAR('a') PORT_CHAR('A')
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_Z)          PORT_CHAR('z') PORT_CHAR('Z')

	PORT_START("LINE.13")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("ESCAPE") PORT_CODE(KEYCODE_ESC) PORT_CHAR(UCHAR_MAMEKEY(ESC))
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("FUNC") PORT_CODE(KEYCODE_TAB) PORT_CHAR(UCHAR_MAMEKEY(LALT))
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_LCONTROL) PORT_CODE(KEYCODE_RCONTROL) PORT_CHAR(UCHAR_SHIFT_2)
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CODE(KEYCODE_RSHIFT) PORT_CODE(KEYCODE_LSHIFT) PORT_CHAR(UCHAR_SHIFT_1)

	PORT_START("BRK")       /* BREAK */
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_NAME("BREAK") PORT_CODE(KEYCODE_F12) PORT_CHAR(UCHAR_MAMEKEY(F12)) PORT_CHANGED_MEMBER(DEVICE_SELF, electron_state, trigger_reset, 0)
INPUT_PORTS_END

static INPUT_PORTS_START( electron64 )
	PORT_INCLUDE(electron)

	PORT_START("MRB")
	PORT_CONFNAME(0x03, 0x02, "MRB Mode")
	PORT_CONFSETTING(0x00, "Normal")
	PORT_CONFSETTING(0x01, "Turbo")
	PORT_CONFSETTING(0x02, "64K")
INPUT_PORTS_END

static INPUT_PORTS_START(electronsp)
	PORT_INCLUDE(electron64)

	PORT_START("ROMPAGES")
	/* TODO: Actual 4bit dip settings are unknown, require a manual */
	PORT_DIPNAME(0x0f, 0x06, "SP64i ROM Pages")
	PORT_DIPSETTING(0x00, "0&1")
	PORT_DIPSETTING(0x02, "2&3")
	PORT_DIPSETTING(0x04, "4&5")
	PORT_DIPSETTING(0x06, "6&7")
	PORT_DIPSETTING(0x08, "8&9 (reserved)")
	PORT_DIPSETTING(0x0a, "10&11 (reserved)")
	PORT_DIPSETTING(0x0c, "12&13")
	PORT_DIPSETTING(0x0e, "14&15")
INPUT_PORTS_END

void electron_state::plus3_default(device_t* device)
{
	device->subdevice<electron_expansion_slot_device>("exp")->set_default_option("plus1");
}

void electron_state::electron(machine_config &config)
{
	M6502(config, m_maincpu, 16_MHz_XTAL / 8);
	m_maincpu->set_addrmap(AS_PROGRAM, &electron_state::electron_mem);

	INPUT_MERGER_ANY_HIGH(config, m_irqs).output_handler().set_inputline(m_maincpu, M6502_IRQ_LINE);

	SCREEN(config, m_screen, SCREEN_TYPE_RASTER);
	m_screen->set_raw(16_MHz_XTAL, 1024, 0, 640, 312, 0, 256);
	//m_screen->set_raw(16_MHz_XTAL, 1024, 264, 264 + 640, 312, 28, 28 + 256)
	m_screen->set_screen_update(FUNC(electron_state::screen_update_electron));
	m_screen->set_video_attributes(VIDEO_UPDATE_SCANLINE);
	m_screen->set_palette("palette");

	PALETTE(config, "palette", FUNC(electron_state::electron_colours), 8);

	SPEAKER(config, "mono").front_center();
	BEEP(config, m_beeper, 300).add_route(ALL_OUTPUTS, "mono", 1.00);

	RAM(config, m_ram).set_default_size("32K");

	CASSETTE(config, m_cassette);
	m_cassette->set_formats(bbc_cassette_formats);
	m_cassette->set_default_state(CASSETTE_PLAY | CASSETTE_MOTOR_DISABLED);
	m_cassette->set_interface("bbc_cass");

	/* expansion port */
	ELECTRON_EXPANSION_SLOT(config, m_exp, 16_MHz_XTAL, electron_expansion_devices, "plus3");
	m_exp->set_option_machine_config("plus3", plus3_default);
	m_exp->irq_handler().set(m_irqs, FUNC(input_merger_device::in_w<1>));
	m_exp->nmi_handler().set_inputline(m_maincpu, M6502_NMI_LINE);

	/* software lists */
	SOFTWARE_LIST(config, "cass_list").set_original("electron_cass");
	SOFTWARE_LIST(config, "cass_list_bbc").set_compatible("bbc_cass").set_filter("ELK");
	SOFTWARE_LIST(config, "cart_list").set_original("electron_cart");
	SOFTWARE_LIST(config, "flop_list").set_original("electron_flop");
	SOFTWARE_LIST(config, "rom_list").set_original("electron_rom");
}


void electron_state::btm2105(machine_config &config)
{
	electron(config);

	m_screen->set_color(rgb_t::amber());

	/* expansion port */
	m_exp->set_default_option("m2105");
	m_exp->set_fixed(true);

	/* software lists */
	config.device_remove("cass_list");
	config.device_remove("cart_list");
	config.device_remove("flop_list");
	config.device_remove("rom_list");
}


void electron_state::electron64(machine_config &config)
{
	electron(config);

	m_maincpu->set_addrmap(AS_PROGRAM, &electron_state::electron_mem);
	m_maincpu->set_addrmap(AS_OPCODES, &electron_state::electron64_opcodes);

	m_ram->set_default_size("64K");
}


void electronsp_state::electronsp(machine_config &config)
{
	/* install mrb board */
	electron64(config);

	/* rom sockets */
	GENERIC_SOCKET(config, m_romi[0], generic_plain_slot, "electron_rom", "bin,rom");
	m_romi[0]->set_device_load(FUNC(electronsp_state::rom1_load));
	GENERIC_SOCKET(config, m_romi[1], generic_plain_slot, "electron_rom", "bin,rom");
	m_romi[1]->set_device_load(FUNC(electronsp_state::rom2_load));

	/* via */
	VIA6522(config, m_via, 16_MHz_XTAL / 16);
	m_via->readpb_handler().set(m_userport, FUNC(bbc_userport_slot_device::pb_r));
	m_via->writepb_handler().set(m_userport, FUNC(bbc_userport_slot_device::pb_w));
	m_via->irq_handler().set(m_irqs, FUNC(input_merger_device::in_w<2>));

	/* user port */
	BBC_USERPORT_SLOT(config, m_userport, bbc_userport_devices, "amxmouse");
	m_userport->cb1_handler().set(m_via, FUNC(via6522_device::write_cb1));
	m_userport->cb2_handler().set(m_via, FUNC(via6522_device::write_cb2));
}


ROM_START(electron)
	ROM_REGION( 0x8000, "mos", 0 )
	ROM_LOAD( "os_basic.ic2", 0x0000, 0x8000, CRC(b997f9cb) SHA1(4a66c83aba07d0a8e76ed8a5545af04e11c19fdc) )
ROM_END

ROM_START(electront)
	ROM_REGION( 0x8000, "mos",  0 )
	/* Serial 06-ALA01-0000087 from Centre for Computing History */
	ROM_LOAD( "basic.rom", 0x0000, 0x4000, CRC(79434781) SHA1(4a7393f3a45ea309f744441c16723e2ef447a281) )
	ROM_LOAD( "elk_036.rom", 0x4000, 0x4000, CRC(dd1a99c3) SHA1(87ee1b14895e476909dd002d5ca2346a3a5f3f57) )
ROM_END

ROM_START(electron64)
	ROM_REGION( 0x8000, "mos", 0 )
	ROM_LOAD( "basic.rom", 0x0000, 0x4000, CRC(79434781) SHA1(4a7393f3a45ea309f744441c16723e2ef447a281) )
	ROM_LOAD( "os_300.rom", 0x4000, 0x4000, CRC(f80a0cea) SHA1(165e42ff4164a842e56f08ebd420d5027af99fdd) )
ROM_END

ROM_START(electronsp)
	ROM_REGION( 0x8000, "mos", 0 )
	ROM_LOAD( "basic.rom", 0x0000, 0x4000, CRC(79434781) SHA1(4a7393f3a45ea309f744441c16723e2ef447a281) )
	ROM_LOAD( "os_310.rom", 0x4000, 0x4000, CRC(8b7a9003) SHA1(6d4e2f8ddc1d829b14206d2747749c4c24789568) )
	ROM_REGION( 0x8000, "sp64", 0 )
	ROM_SYSTEM_BIOS( 0, "101_2", "v1.01 (2x16K)" )
	ROMX_LOAD( "sp64_101_1.rom", 0x0000, 0x4000, CRC(07e2c5d6) SHA1(837e3382c376e3cc1ae42f1ca51158657ef2fd73), ROM_BIOS(0) )
	ROMX_LOAD( "sp64_101_2.rom", 0x4000, 0x4000, CRC(3d0e5dc1) SHA1(89743c43b24950d481c150fd4b4de985600cca2d), ROM_BIOS(0) )
	ROM_SYSTEM_BIOS( 1, "100", "v1.00 (32K)" )
	ROMX_LOAD( "sp64_100.rom", 0x0000, 0x8000, CRC(4918221c) SHA1(f185873106e7e7225b2e0c718803dc1ec4ebc685), ROM_BIOS(1) )
	ROM_SYSTEM_BIOS( 2, "100_2", "v1.00 (2x16K)" )
	ROMX_LOAD( "sp64_100_1.rom", 0x0000, 0x4000, CRC(6053e5a0) SHA1(6d79e5494349f157672e7c59949f3941e5a3dbdb), ROM_BIOS(2) )
	ROMX_LOAD( "sp64_100_2.rom", 0x4000, 0x4000, CRC(25d11d8e) SHA1(c1bceeb50fee1e11de7505a3b664b844cfb56289), ROM_BIOS(2) )
ROM_END

#define rom_btm2105 rom_electron


/*     YEAR  NAME        PARENT    COMPAT  MACHINE     INPUT       CLASS             INIT        COMPANY                             FULLNAME                                 FLAGS */
COMP ( 1983, electron,   0,        0,      electron,   electron,   electron_state,   empty_init, "Acorn Computers",                  "Acorn Electron",                        MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS | MACHINE_SUPPORTS_SAVE )
COMP ( 1983, electront,  electron, 0,      electron,   electron,   electron_state,   empty_init, "Acorn Computers",                  "Acorn Electron (Trial)",                MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS | MACHINE_SUPPORTS_SAVE )
COMP ( 1985, btm2105,    electron, 0,      btm2105,    electron,   electron_state,   empty_init, "British Telecom Business Systems", "BT Merlin M2105",                       MACHINE_NOT_WORKING )
COMP ( 1987, electron64, electron, 0,      electron64, electron64, electron_state,   empty_init, "Acorn Computers / Slogger",        "Acorn Electron (64K Master RAM Board)", MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS | MACHINE_SUPPORTS_SAVE )
COMP ( 1991, electronsp, electron, 0,      electronsp, electronsp, electronsp_state, empty_init, "Acorn Computers / Slogger",        "Acorn Electron (Stop Press 64i)",       MACHINE_IMPERFECT_SOUND | MACHINE_IMPERFECT_GRAPHICS | MACHINE_SUPPORTS_SAVE )