Reprogrammable Genesis Cartridge

Build a reprogrammable cartridge. Many applications or games can be developed and tested on actual hardware rather than using an emulator. For those interested in Genesis development, the technical documentation available at Zophar serves as a valuable starting point. It is possible to listen to Genesis music (.gym) on a real Genesis console. A ROM called Flavio's GYM Player requires a .GYM file to be appended. Once loaded, the ROM plays the gym file. It is also possible to download real game ROMs for use with this cartridge; however, this practice is illegal. Some individuals claim that erasing the ROM within 24 hours makes it legal to use, but this is uncertain and not legally confirmed. Many of these games are no longer sold and may be considered abandonware, though the legality of this status is also questionable. The second version of the cartridge supports games up to 1024K (1MB) using two AT49F040 512K flash chips. This new version can accommodate two games of 512K each, allowing users to switch between them by pressing the console's reset switch. A jumper selects between the 1x1024K and 2x512K modes. The schematic for the second version is provided. The first version used AT49F002 flash chips and lacked a 74LS90 for bank alternation, with the A18 signal left unconnected since the flash chip addressing stops at A17. Programming the flash chips is accomplished using an old universal programmer from Xeltek, which can be purchased on eBay for approximately $50. Alternatively, a custom programmer can be built, as the flash datasheet includes programming instructions. The universal programmer accepts DIP chip packages and can program other package types with an adapter. Larger flash chips than 512K in DIP packages are not readily available. Although it would have been possible to solder larger flash chips onto the PCB, an adapter would have been necessary for programming. Genesis ROMs typically come in SMD (Super Magic Drive) format and must be converted to raw binary before they can be programmed into the flash chips.

The reprogrammable cartridge design allows for significant versatility in developing and testing software for the Genesis console. The architecture utilizes two AT49F040 flash memory chips, each providing 512K of storage, which enables the simultaneous use of two 512K games or a single 1024K game. The incorporation of a reset switch facilitates easy game switching, enhancing user experience without the need for additional hardware intervention. The jumper configuration for selecting between memory modes ensures that the cartridge can be tailored to specific game requirements, making it adaptable for various applications.

The schematic design reveals the connections necessary for the flash chips, including power supply lines, data lines, and control signals. The absence of the 74LS90 in the first version indicates a more straightforward approach to memory management, though it limited functionality compared to the second version. The programming process for the flash chips highlights the importance of compatibility with various chip packages and the need for conversion from SMD to raw binary format, ensuring that developers can utilize existing ROMs effectively.

Overall, this cartridge serves as a practical tool for developers interested in creating new content for the Genesis platform, providing both the hardware capabilities and the potential for software experimentation. The design choices reflect a balance between complexity and functionality, catering to both novice and experienced developers in the retro gaming community.Build a reprogrammable cartridge. Many things can be done with such a cartridge: You can develop your own applications or games and try them on real hardware instead of using an emulator. If you`d like to get into genesis development, I think the genesis technical documentation available at zophar is a good starting point.

You can listen to genesis music (. gym) on a real genesis. There is a rom named Flavio`s GYM Player which needs to have a. GYM file appended to it. Once loaded, the rom plays the gym file. Yes, it`s possible to download real games roms and use them with this cartridge. Unfortunately, it`s illegal. Some people say that if you erase the rom within 24 hours, it`s legal to use them. (I dont know if it`s true, I am not a lawyer). Since many of those games are not sold anymore and have been `abandonned` by the company owning the copyright, they may be considered as abandonware. (And even then, I`m not sure if it`s legal) Here are a few pictures of the second version, which supports games up to 1024K (1Meg) by using 2 AT49F040 512K flash chips.

This new version can also hold 2 games of 512K each. Each time the console`s reset switch is pressed, the current game is changed. A jumper selects between the 1x1024K and 2x512K mode. Here`s the second version schematic. I used two AT49F040 512K flash chips. The cartridge can hold a game of 1024K (1Meg) or 2 512K games. When 512K games are used, we can alternate between them by pressing the reset switch on the genesis: The first version which used AT49F002 flash chips did not have the 74ls90 to alternate between banks. The A18 signal was simply not connected since the flash chips addressing stops at A17. To program the flashs, I use an old universal programmer from xeltek. You can buy an universal programmer from ebay for approximately 50$ US. You may also build your own programmer since the flash datasheet explain how to program them. My universal programmer only accepts dip chip packages. It can program other types of package with an adaptor. I was not able to find flash chips bigger than 512K with a dip package. I could have soldered bigger flashes on my pcb but I would have had to build an adapter to program the cart.

Genesis roms ususally comes in. smd (Super Magic Drive) format. You cannot simply program them in the flash chips, they must be converted to raw binary first. 🔗 External reference