SNES Reproduction Quick Guide – Custom PCB

Please look at the main entry for more information!

Here I will detail to you a quick and dirty guide to making SNES repros using my custom boards. There’s a lot more detail over on the main tutorial, but here I will forgo a lot of the detailed information about programming different chips and instead just focus on how to use the board itself.

Parts Needed

Here’s a breakdown of what parts you need based on what kind of game you’re making. All parts are located on the front of the board (except for the 257 multiplexers, which are located on the back of the 27C322 boards).

pcb_322_2_2

pcb_snesmask_2_2

M27C322 / SNES MASK ROM – EPROM or EEPROM

Needed for: Every game
Part Number: Various EPROMs or EEPROMs noted in the main tutorial, the most common of which being M27C322 (or equivalent, for use in 27C322 boards), and M27C801 and 29F033 (or equivalent, for use in the SNES Mask ROM boards)
Function: Holds the ROM file

C1 – Electrolytic Capacitor

Needed for: Every game
Value: ~22 uF, at least 10 V rated
Function: Lowers ripple voltage on the voltage rail to the SNES, holds up voltage for saving after console turns off, noise filtering, etc. (prevents errors)

C2, C4 – Ceramic Capacitors

Needed for: Every game
Value: ~0.1 uF, at least 10 V rated
Function: Filters noise on the voltage rails of the chips (prevents errors)

C3 – Ceramic Capacitor

Needed for: Any game that saves
Value: ~0.1 uF, at least 10 V rated
Function: Filters noise on the voltage rails of the SRAM chip (prevents errors)

CIC – Region Lock-out Chip

Needed for: Every game (on un-modded SNES systems)
Part Number: 12F629
Function: Fakes out the region lock-out chip used in the SNES to let you play the game

R1, R2, D1, D2 – Resistors and Diodes

Needed for: Any game that saves
Value: ~220 Ω for resistors, 1N914 or equivalent for diodes
Function: Combines the battery and SNES voltage rails to power the SRAM and keep it working after the SNES power is turned off

Battery – C2032 Coin Cell Battery

Needed for: Any game that saves
Part Number: C2032 (3 volt battery)
Function: Keeps the SRAM powered on after SNES is turned off (keeps your save data)

SRAM (256K or 64K) – SRAM Chip

Needed for: Any game that saves
Part Number: 62256 (256K size), 6264 (64K size)
Function: Holds the save data for games that save

SRAM Decoder – Memory Decoder Chip

Needed for: Any game that saves
Part Number: 74HCT139 (or equivalent)
Function: Tells the cartridge when to use the SRAM and when to use the EPROM, based on the area of the memory map being accessed

322 Muxes – Multiplexers (27C322 Reproduction Board ONLY, on backside)

Needed for: Every game
Part Number: 74HCT257 (or equivalent)
Function: Maps the data from the 27C322 (which uses a 16-bit bus) to the SNES cartridge (which uses an 8-bit bus)

Solder Pads (backside)

There are a handful of solder pads you’ll need to bridge on the back of the board in order to make your game work. These are shared between both versions of the board, but there is an extra set on the SNES Mask ROM board, which is detailed at the end).

pcb_322_2_2_back

HiROM/LoROM Selection (bottom right of the board)

These are a set of three-way solder pads. You need to bridge two of the three (the middle and one to the left or right) depending on what bank type your game is. If it is the HiROM bank type, solder the two right pads together in each set of three; if it’s the LoROM bank type, solder the two left pads together in each set of three. See below: solder the pads in blue, leave the other side disconnected.

hiromlorom.PNG

NOTE: If you’re making a LoROM game and you are not using the SRAM decoder (if your game does not save) you will need to solder ALL THREE connections together on the bottom right hand of the box. This is because the SRAM decoder takes care of activating the EPROM/EEPROM on LoROM boards, so if you don’t have a decoder because your game doesn’t save, you will need to bypass the signal.

loromnosram

SRAM Power (top left of the board)

If you’re using the SRAM, bridge these pads together. If you reprogram your EPROM with a new game, you should disconnect these pads by desoldering them to reset the SRAM (they only need to be disconnected for a second). Then, resolder them together for your new game.

SRAM SIZE (SRAM selection pads)

These are another set of three-way solder pads. You need to bridge two of the three (the middle and one to the left or right) depending on the size of the SRAM your game uses. See the table below. Solder the pads in blue, leave the other side disconnected.

sramselect.png

EPROM/EEPROM Power (Bottom left of the SNES Mask ROM board ONLY)

I added pads for the two VCC pins (pin 34 and 36) on the SNES Mask ROM pinout. They need to be all soldered together in order to power the EEPROM/EPROM.

pcb_snesmask_2_2_back_solder.jpg

I added these pads because if you’re using the TSOP Adapter Board that fits in the 36 pin SNES Mask ROM pinout, these pins need to be disconnected from main board power rails if you want to program the TSOP while the adapter is in the Mask ROM socket (otherwise, the TL866 will power the entire cartridge, which is too much current for the programmer to handle). You can program or reprogram the EEPROM while mounted on the SNES board if you use long enough pins that stick out the back of the Mask ROM socket. You can fit the extended pins inside the TSOP Adapter (III) to TL866 Adapter, and then attach it to the TL866 programmer. Once you’ve programmed the chip, you’ll need to resolder the three pads together.

68366115_391441694890650_921009295145828352_n

Here’s what my prototype board looks like when placed onto the adapter. Note that I’ve had flaky success doing this – sometimes the chips don’t like to program when placed in the SNES board. I suspect this is due to long traces acting like antennas on the cartridge PCB that might be interfering with the programming step. I’m currently developing some new adapters that might yield more repeatable results, until this is ironed out, it’s just a nice feature that may or may not work. Right now, it’s probably easier to just get a board to specifically use for prototyping with the TSOP adapter boards instead.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s