Introduction

The MCC is a 8 and 16 bit Do-It-Yourself console development system using standard TTL logic and standard RAM chips in a modular design. Currently the Sega Genesis/Mega Drive and the Nintendo SNES are supported, but it shouldn't be a problem to add support for more consoles, too. It is also possible to use Flash ROMs or other types of SRAM in the system, you have just to take care of the speed (at the *very* least 70ns) and the pinouts.
Keep in mind that this device is intended to copy your home-grown software (you can use GCC to develop software for the Genesis) and run it on the actual hardware. You are not allowed to pirate commercial ROMs with this system. I'm also not responsible for anything you do to your hardware or software. If you want to build the system, you should know what you're doing. The system has been built by me and it works both on the SNES and the Genesis without any problems.

The MCC system consists of

• The main RAM board. It carries up to 8 RAM chips resulting in a total of 32MBits.
• Two extension carts of which one at a time is attached to the RAM board and determines the width of the data bus (8 or 16 bits). It also supplies the RAM board with power.
• A battery backed RAM cart for save games.
• One or more console-specific boards which ties the RAM board and battery backed RAM together and connects them to the console. Currently there's one board for the Genesis/Mega Drive and one for the SNES.
• The parallel port I/O cart for the computer. It is used to program the RAM board and the battery backed RAM cart.

Datasheets:

• 1N4148 (Diode for digital circuits) 1N4148.pdf (41kb)
• 2N3904 (NPN Digital Transistor) 2N3904.pdf (65kb)
• KM684000B (512kx8 CMOS Static RAM<) KM684000B.pdf (179kb)
• LP621024D (128kx8 CMOS Static RAM) LP621024D.pdf (155kb)
• NEC µPD71055C/P8255 (Programmable Parallel Interface) NEC_UPD71055_P8255A.pdf (732kb)
• SN74LS02 (Quad 2-Input NOR Gate) SN74LS02.pdf (36kb)
• SN74LS04 (Hex Inverter) SN74LS04.pdf (35kb)
• SN74LS138 (1-of-8 Demultiplexer) SN74LS138.pdf (69kb)
• SN74LS157 (Quad 2-Input Multiplexer) SN74LS157.pdf (52kb)
• SN74LS21 (Dual 4-Input And Gate) SN74LS21.pdf (34kb)
• SN74LS688 (8-Bit Comparator) SN74LS688.pdf (90kb)
• SN74LS74 (Dual D-Type Flip Flop) SN74LS74.pdf (54kb)

Schematics:

• Main RAM Cart
• Schematic: ramcart.gif (1674x1098, 70kb)
• Prototype photo: ramboard.jpg (638x836, 127kb)
• 8bit Extension
  • Schematic: 8bit-extension.gif (1287x1149, 45kb)
• 16bit Extension
• Schematic: 16bit-extension.gif (1200x1105, 37kb)
• Battery Backed RAM Cart:
  • Schematic: battery-ram.gif (1242x1133, 27kb)
  • Prototype photo: battery-ram.jpg (618x525, 88kb)
• SNES Board:
• Schematic: snesboard.gif (1957x3565, 120kb)
• Prototype photo: snesboard.jpg (618x987, 191kb)
• Genesis Board:
• Schematic: genesisboard.gif (940x765, 28kb)
• Parallel Port I/O Cart (Used to program the RAM carts):
• Schematic: pio.gif (2237x2066, 94kb)
• Prototype photo: pio.jpg (962x624, 186kb)

Additional Information: Nintendo SNES

Before you can operate any selfbuilt circuit on the SNES, you'll have to disable a chip inside the unit called the CIC, Security or Lockout Chip. It prevents any cartridge (or copier) from running if it doesn't have such a chip, too. Disabling the chip inside the SNES is relatively easy and involves disconneting pin 4 of it. The chip is labeled F411, F413A, F411A or similar. Go to the gamesx website to find a description of the process with a few pictures.

The pinout of the SNES cartridge connector:

Pin	Name	Pin	Name
5	GND	36	GND
6	A11	37	A12
7	A10	38	A13
8	A9	39	A14
9	A8	40	A15
10	A7	41	A16
11	A6	42	A17
12	A5	43	A18
13	A4	44	A19
14	A3	45	A20
15	A2	46	A21
16	A1	47	A22
17	A0	48	A23
18	/IRQ	49	/ROM
19	D0	50	D4
20	D1	51	D5
21	D2	52	D6
22	D3	53	D7
23	/RE	54	/WE
24	CIC	55	CIC
25	CIC	56	CIC
26	/RAM	57	nc
27	5V	58	5V

Both the ROM and battery backed RAM aren't mapped into the SNES' address space in a linear fashion but are rather scattered, plus there are two different ROM/SRAM configurations called LOROM and HIROM which makes the resulting mapper circuit of the SNES board relatively complex. The address lines a16..a23 are referred to as the bank number and a0..a15 as the address. This is just a naming convention and doesn't imply the need of any special circuitry.


LOROM configuration:

ROM
SNES bank	SNES address	ROM address
$00..$6F	$8000..$FFFF	$000000..$37FFFF
$80..$EF	$8000..$FFFF	$000000..$37FFFF
SRAM
SNES bank	SNES address	SRAM address
$70..$77	$0000..$7FFF	$000000..$03FFFF

HIROM configuration:

ROM
SNES bank	SNES address	ROM address
$40..$6F	$0000..$FFFF	$000000..$2FFFFF
$C0..$FF	$0000..$FFFF	$000000..$3FFFFF
$00..$3F	$8000..$FFFF	Mirror of banks $C0..$FF
$80..$BF	$8000..$FFFF	Mirror of banks $C0..$FF
SRAM
SNES bank	SNES address	SRAM address
$70..$77	$0000..$7FFF	$000000..$03FFFF
$00..$0F	$6000..$7FFF	$000000..$01FFFF
$10..$1F	$6000..$7FFF	$000000..$01FFFF
$20..$2F	$6000..$7FFF	$000000..$01FFFF
$30..$3F	$6000..$7FFF	$000000..$01FFFF
$80..$8F	$6000..$7FFF	$000000..$01FFFF
$90..$9F	$6000..$7FFF	$000000..$01FFFF
$A0..$AF	$6000..$7FFF	$000000..$01FFFF
$B0..$BF	$6000..$7FFF	$000000..$01FFFF

Additional Information: Sega Genesis

The cartridge connector pins of the Genesis are numbered A1-A32 and B1- B32, left to right, with the A-row towards the back and the B-row towards the front. The ROM is mapped directly into the first 2 meg words (=4 meg bytes) of the Genesis' address space, so there is no additional logic needed.

Pin	Name	Pin	Name
A1	GND	B1	?
A2	5V	B2	!H_RESET
A3	A8	B3	?
A4	A11	B4	A9
A5	A7	B5	A10
A6	A12	B6	A18
A7	A6	B7	A19
A8	A13	B8	A20
A9	A5	B9	A21
A10	A14	B10	A22
A11	A4	B11	A23
A12	A15	B12	VIDEO
A13	A3	B13	VSYNC
A14	A16	B14	HSYNC
A15	A2	B15	HS_CLK
A16	A17	B16	!C_OE
A17	A1	B17	!C_CE
A18	GND	B18	!AS
A19	D7	B19	CLK
A20	D0	B20	!DTACK
A21	D8	B21	?
A22	D6	B22	D15
A23	D1	B23	D14
A24	D9	B24	D13
A25	D5	B25	D12
A26	D2	B26	!LO_MEM
A27	D10	B27	!RESET
A28	D4	B28	!LDSW
A29	D3	B29	!UDSW
A30	D11	B30	!S_RESET
A31	5V	B31	?
A32	GND	B32	!CART_IN

Software:

There's finally some software available and more will follow. For now, there is:


SNESXfer v0.01b (8kb), the transfer software for SNES ROMs



GenXfer v0.01b (6kb), the transfer software for Sega Genesis ROMs