Making A MegaFlashROM SCC of 512kB
This page was last modified 10:33, 2 August 2016 by Gdx. Based on work by RetroTechie and PAC.

Contents

Making a FlashRom SCC 512K

Here we are again. This time we are going to be building a simple 512K FlashRom SCC cartridge. This tutorial is going to be simple and dirt-cheap. During the last RU of December 2013 I bought an F1 Spirit cartridge that was in a not-so-good condition. It didn’t have a ROM and had some sort of home made audio output. But it was cheap and it was perfect to investigate the SCC chip without having to ruin a good cartridge. Personally I feel bad about destroying a perfectly good game for tinkering around, especially with the rising prices of good cartridges, even more for SCC cartridges.

So I went into Google and found out that the SCC chip is not only an audio chip, it also has some extra stuff that’s even better than the SCC audio. Besides the audio capabilities, this chip adds a memory mapper of up to 512KB or 4 Megabits. Before moving forward, I would like to thank everyone that has posted information about this chip online, and those individuals that have created the different programs to use this extra functionality.

FlashROM FOTO1.png

Components

It turns out, if we just want to get a 512K flash memory and SCC sound, the resulting schematics are pretty simple, actually make that incredibly simple. Additionally, the required components, besides the SCC cartridge, are very affordable and easy to obtain. This is because the Flash Eprom AM29F040B is a memory that was used on the motherboard of old Personal Computers (PC) to keep the BIOS information. So, it’s very likely that you may even have the required components somewhere around your house. Just look for an old PC motherboard and look at the BIOS chip. If you see the above reference, this is your lucky day.

The next and last required component is a two-way selector switch that we can easily find in any hobby supply or even scrounge from old electronic equipment.

And that’s it. You will also need soldering iron, solder, wires, a 4.7 kΩ resistor and that’s pretty much it. Nothing else. If you have a Dremel or a multi tool to make a hole for the switch and a hot glue gun, that would make things easier.

Of course this is the best-case scenario, if you don’t have any of these available, you will need to get out of the house and purchase all these items. If this is your case, you can obtain all of the required components (except for the tools) for less than 10Euros.

Let’s get started

The first step is to open up the cartridge. Opening one of these is not easy, as they have multiple tabs around them, so the outcome is normally a couple of broken tabs. I haven’t been able to find any way around it. Start by making pressure at the cartridge slot and separate the enclosure carefully. Once opened, remove the board from the cartridge and choose a good spot in the cartridge for the switch.

As a recommendation, you can place the switch at the right upper corner of the cartridge. If needed, the board can be cut at that corner so that the switch fits, which is ok as there are no tracks on that side of the board.

If we pay attention to the board, there seem to be three different models. Look at the schematics below to find out which particular model you have. In this case, I am going to be working on a Model A board (more about different models below). By the way, if you have an SCC+ cartridge, things are very different and, in fact, this document does not cover SCC+. The SCC+ has even more features than the SCC like mapping of SRAM and that’s why the SCC+ chip has more pins. I don’t have an SCC+ and I wouldn’t dare to destroy one if I did.

FlashROM FOTO2.png

In the above picture you can see the board we are going to be working on. This board has been modified, for instance it is missing the ROM. The ROM is (or was, in this case) located at the empty spot that can be seen at the top of the board. This is exactly what you need to do in order to get your board ready: unsolder the ROM. Explaining how to unsolder this type of component is beyond the scope of this tutorial.

Schematics

Please take a look at the following schematics, as this is what we are going to be doing:

MegaFlashRom Schematic

Notes:

  • Adapting a 4Mbit Flash Rom for the SCC Chip 2212P003. There are three different cartridge board models:
  • Model A: It has two rows of 9 unconnected holes.
  • Model B: It does not have a 9-hole row.
  • Model C: The row of resistors is parallel to the chips.
  • In the Model A, the Vcc pin coincides with a hole that turns out to be Vcc, so that it can be reused.
  • Unless explicitly mentioned, all chip pins coincide with the holes on the board.

Resistor is connected between +5V and the (EP)ROM's /CE input, such that /CE input isn't ever left unconnected (aka "floating"), but instead is 'pulled high' (EPROM disabled) whenever switch is open or halfway between contacts. Resistor value isn't critical - anywhere from around 1~47 kΩ will do, 4.7 kΩ is a good value. It may be practical to solder resistor to non-component side of the circuit board.
Switch is then connected between that /CE input and point where the signal originally came from. In this case: /SLTSL (SCC chip pin 10).

Don’t panic yet! It’s not that hard. Look the schematics again and compare with your cartridge board. Now identify the two chips. The one in the left (the longest one) is the SCC chip. The one in the right is the flash memory. The next step is to locate the first pin (Pin 1). This can be found at the left side of the chip notch, as depicted in the schematics.

Look again at the schematics. If there is no wire depicted between two points, it means these are already connected and there is no need to wire them. Actually, if you look closely, you only need seven wires plus the ones for the switch.

Assembly

For the pins of the Flash memory that we need to wire, we will bend these so that they are facing outwards, like shown in the below picture.

FlashROM FOTO3.png

If you have a Model A board, there is no need to bend the last pin (Pin 32), as there is a Vcc soldering point right under this pin, so we can leverage that. Now we need to solder the memory to the board like shown in the following picture.

FlashROM FOTO4.png

As you can see, the chip has more pins than available holes on the board, but we will place the chip so that the first (1 and 2) and the last pins (31 and 32) are outside of the board holes. Since these are the pins that we are going to be wiring, we bent these in the previous step.

At this point, you may want to trim the pins so that they are not too long and interfere while working in the area, and place some soldering iron on them so that you let them ready for wiring. Now you are ready for wiring the pins as shown in the schematics.

FlashROM FOTO5.png

In the above picture you can see the final result, with the board inserted into the cartridge. This is what you should have once you are finished. Also, take a look at the switch on the right side, which is glued to the cartridge with hot glue.

Once you have wired the chips, the switch is the next thing you need to wire. Please look at the picture to have an idea on where to place the resistor for the switch. As you can see, there are not too many wires, and the only modification done is mostly adding wires.

Now you can close the cartridge and try it! Once you are absolutely sure that everything is working, you can glue the cartridge using hot glue so that it is safe for future use. Because we are using hot glue instead of CA (Loctite) we can still open it later.

FlashROM FOTO6.png

And you are done! In the above picture you can see the cartridge in use on my FS-A1F.

In order to use your new 4 Megabit Flash Memory there is software available that should detect it and use it by just following the instructions.

Lastly, an interesting note if you don’t have an EPROM programmer. If instead of soldering a Flash Memory on the empty spot you solder a chip slot, you will be able to use the board as an EPROM programmer. You will need to “tell” the software to ignore any adaptation or modification (there is an existing parameter for this). The only problem with this experiment is that the combination of chip slot and chip will not fit inside the cartridge.

Enjoy your new FlashRom!

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