Introduction

When I was designing my SMS (non-Japanese) to Megadrive/Genesis cartridge adapter, I learned that the Japanese version of this console used a different connector (44 pins instead of 50). So I decided to also design an adapter for Japanese cartridges. The schematics for this new adapter are presented here.

Specifications:

• Supports Sega MarkIII/Japanese Master system cartridges.
• Tested on Mega Drive I and II (North-american and Japanese systems).
• .STL files available to print your own enclosure.
• Not compatible with Genesis 3

Here are a few pictures of the resulting adapter:

Usage

Most of the time, installing the adapter (in the correct direction), inserting the cartridge and applying power is all that is needed. But there can be some issues depending on the game:

1) Controller problems
Some games won't work properly using Megadrive controllers. A solution is to Master System controllers instead, or to build a special adapter.

2) Start-up problems
When an SMS game is run on a Megadrive console, there is no bios to run before the game. The CPU executes the game right from the start. This can be a problem for games which rely on intialization normally performed by the bios, in particular setting up the stack pointer. (I learned about this thanks to reference #5)

A quick workaround to this is to first run SMS game that does not have this problem, turn off the power, insert the non-starting game and reapply power. Now the game should start. This is because even following the power cycle, the stack pointer register bits haven not faded away yet and are still at the last value used!

February 2015: The above manipulations can be avoided by adding a stack initialisation circuit!

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My collection of japanese titles is not very large, but here are those that are tested:

Title	Megadrive controller (1)	Stack pointer (2)
ファンタシースター(Fantasy Star)	Ok	Ok
星をさがして…(Hoshi wo sagashite)	Ok	Not setup
熱球甲子園(Nekkyu Koushien)	Ok	Not setup
ソロモンの鍵・王女リヒタの涙(Solomon no Kagi - Oujo Rihita no Namida)	Ok	Not setup
スケバン刑事II・少女鉄板面伝説(Sukeban keiji - shoujo tekkamen densetsu)	Ok	TBD
ギャラクティック　プロテクター(Galactic Protector)	N/A (Paddle)	Ok
ファンタジーゾーンII オパオパの涙(FANTASY ZONE II The tears of OPA OPA)	Ok	Ok
アレックスキッドのミラクルワールド(Alex Kidd no Miracle World)	Ok
スペースハリアー(Space harrier)	Ok
アストロウォーリアー(Astro Warrior)	Ok
グレートボレーボール(Great volleyball)	No. Use SMS controllers.
赤い光弾 ジリオン(Red photon zillion)	Ok
トライフォーメーション(Zillion II: The Tri-Formation)	Ok
あんみつ姫(Anmitsu hime)	Ok
アフターバーナー(After burner)	Ok
孔雀王(kujaku ou / Spellcaster)	Ok
どきどきペンギンランド宇宙大冒険(Penguin Land)	No. Use SMS controllers.
ザ・キャッスル(The castle)	Does not work because it is an SG-1000 game.[1]
Gamboy game:[2] Super columns	Does not work.

Please report if you try other games. I'd like to list them here.

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^[1] Games compatible with the Sega SG-1000/SC-3000 are not supported. Only Mark-III exclusive (マークIII専用) games will work.
^[2] The Gamboy is a Korean version of the Sega Master System. It would seem that most GamBoy games are in fact SG-1000 games. But I'm told one possible exception is Super Boy 4.

Schematic

Here is the schematic. I used my previous adapter project as a base and consulted the same références.

Components marked "NP": For this adapter too, I placed a few 0 ohm resistors for easy rewiring of selected signals, just in case. (In the schematic, resistors maked as "NP" are not to be normally installed.


Errata: I made a mistake on the CE (Chip Enable) signal wiring. On the SMS side, it should be wired to pin 19 (MREQ) instead of pin 17. A small piece of wire must therefore be installed between those two pins, otherwise nothing works. This fix is shown in red in the schematic and pictured on the right.

PCB

I designed and had a PCB built specifically for this project. Basing my adapter on a rewired SMD cartridge would have taken too much time. I kept height of the PCB low as I did not wish to have the SMS cartridge hanging too high when using the adapter. (The MarkIII cartridge is already tall enough!)



Here is the PCB as it was built. It is available, in kit or ready to use, in my online store.


The MarkIII cartridge connector has 44 pins with a .125" (3.18mm) pitch. The one I used is Edac Inc. p/n: 346-044-520-202. As it was meant for through-hole soldering, installing it on a PCB edge like I do here requires bending the pins..

Enclosure v1

I designed and printed a casing for the adapter. Here is the .STL file should you want to print one:
sms2smd_m3_casing.zip



February 2015: I discovered that the above enclosure is not usable with the Megadrive 1!.

Enclosure v2

I happens that what was a design I was satisfied with on-screen ends up being a bit disappointing in reality. This was the case with the first enclosure I show above. After reworking it a bit, here is the result:




Should you want to print an identical casing, here is the .STL file:
sms2smd_m3_casing_v2.zip

February 2015: I confirm that this version of the enclosure works without problem with the Megadrive 1 too.

Controller fix

There are a few games that will not work properly with Genesis/Megadrive controllers. A solution is to use SMS controllers, but it is also possible to build this compatibility adapter. The idea is to keep the SELECT signal on the controller side high through a resistor (100kΩ).



I don't personally own any games where this adapter is necessary, so I have not built one. But ishiyakazuo who suggested this solution says it works great.

There is a list games needing this fix in the db-electronics forum:
http://db-electronics.freeforums.net/thread/12/genesis-controller-compatibility

As of 2014-10-31, the games known to require SMS controllers or the fix presented here were:

• Alien Syndrome
• Bomber Raid
• Great Volleyball
• Montezuma's Revenge
• Shanghai
• Where in the World is Carmen Sandiego?
• Wonder Boy in Monster Land

I assume the Japanese version of those games, if available, may exhibit the same issue.

Japan-only games

According to the List of Master System games on Wikipedia, the following are the games that have not been published outside Japan. I think I will discover a few using my adapter..

Alex Kidd BMX Trial	Argos no Juujiken アルゴスの十字剣	The Castle ザ・キャッスル
Comical Machine Gun Joe	Galactic Protector ギャラクティック　プロテクター	High School! Kimengumi ハイスクール！奇面組
Hoshi wo Sagashite... 星をさがして…	Loretta no Shouzou	Machinegun Joe
Mahjong Sengoku Jidai	Megumi Rescue め組レスキュー	Nekyuu Kousien 熱球甲子園
Pit Pot	Satellite 7	Solomon no Kagi - Oujo Rihita no Namida ソロモンの鍵・王女リヒタの涙
Sports Pad Soccer	Sukeban Deka II スケバン刑事II・少女鉄板面伝説	Super Racing
Tensai Bakabon	Woody Pop

References

#	Link	Description/comments
1	http://www.smspower.org/forums/viewtopic.php?t=6875	SMS to SMD adapter wiring table.
2	http://nfggames.com/forum2/index.php?topic=3991.0	Pictures of the internals of a non-Sega commercial adapter named "Datel Pro Mega Master". What a name!
3	http://www.hardwarebook.info/Mega_Drive_Cartridge	SMD cartridge pinout.
4	http://www.smspower.org/maxim/Documents/Pinouts	Pictures and pinouts for a SMS cartridge. This was of great use to double-check that I made no mistake with the connector orientation. There's also information on the connector used on Japanese systems which should be useful if I make a Japanese version of this adapter.
5	http://www.smspower.org/forums/viewtopic.php?t=14084	A very interesting discussion which begins with technical information on the custom chip Sega uses in it's own adapter (It looks like this chip initializes the stack, required for some games). Farther in the discussion, there is a schematic (sega2sms.png) a bit difficult to follow, but useful, and matching the wiring table above in reference 1

Disclaimer

I cannot be held responsible for any damages that could occur to you or your equipment while following the procedures present on this page. Also, I GIVE ABSOLUTELY NO WARRANTY on the correctness and usability of the informations on this page. Please note, however, that the procedures above have worked in my case without any damages or problems.

Now you cannot say that I did not warn you :)