SGC Reprogrammable

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By Alexey

Paragon (1233)

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16-10-2017, 22:42

I always wanted to have a cheap reprogrammable cartridge for small games and test utilities. So I designed a simple board to allow reprogramming an EEPROM on the SGC (Small Games Cartridge) board:

The cartridge is inserted into a 50 pin slot on another special board and that board is then inserted into an EEPROM programmer. Using the W27C512 chip's settings a 64kb image can be quickly written directly into the SGC's EEPROM chip. Simple and easy:

The only inconvenience is that the cartridge needs a 64kb image. This means that a 16kb game ROM has to be appended to itself 4 times. Also 32kb ROMs need to swap their first and second 16kb parts if CS mode is used, for RD mode this is not necessary. I will write a small utility to make a 64kb image out of any ROM that is smaller than 64kb.

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By Pencioner

Master (212)

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16-10-2017, 23:33

Nice thing Smile

By Alexey

Paragon (1233)

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16-10-2017, 23:59

This pair of boards will be mostly used for the diagnostics cartridge development and testing. Basically with RD mode a developer gets a full 64kb area for his needs. I can even load Yamaha's Painter (64kb image) into this cartridge and then call it with _PAI command from Basic.

By hardwaremaker

Expert (125)

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17-10-2017, 00:10

Great idea !!!

By Alexey

Paragon (1233)

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17-10-2017, 12:33

I have a few cartridge and adapter boards as well as 50 pin slots for sale, so if anyone is interested, please send me an e-mail.

By Alexey

Paragon (1233)

Alexey's picture

22-10-2017, 23:39

I've made a program in AutoIT to convert ROMs into a 64kb image for writing into the W27C512 EEPROM. It does all necessary checks and swaps the halves of 32kb ROMs to work properly. The UI is quite simple:

With the "Change Mode" button you can select different modes: RD, CS12, CS2 and CS1. The solder jumper moves to the appropriate pad with every pressing of this button. The program itself can be downloaded from here:

http://podrezov.com/sgc/SGC_ImageCreator.exe

By Alexey

Paragon (1233)

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23-10-2017, 23:23

The software has been uploaded into my repository:

https://github.com/Wierzbowsky/SGC_ImageCreator

By Louthrax

Paragon (1695)

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02-11-2017, 12:54

When reading this I was wondering how hard it would be to change the board in order to program it directly from MSX? Is that even possible? (are the MSX voltages OK for that?).

By Grauw

Enlighted (6262)

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02-11-2017, 13:07

You can put a FlashROM rather than an EPROM into the cartridge’s ROM socket right? Plain ROMs can be flashed, and I think ASCII type ROMs as well... I think the Konami mappers aren’t suitable for it though, because you can’t write without triggering the bank select.

By Alexey

Paragon (1233)

Alexey's picture

02-11-2017, 13:31

We already have the commercial cartridge platform that has a FlashROM and a small Altera chip with the multi-mapper support. This cartridge can be programmed directly on MSX. But that's another story. This particular small cartridge was designed exactly for the purpose of being reprogrammed in an EEPROM burner to make it super cheap. Why to waste a flash chip when you can put an EEPROM?

This cartridge was made for the purpose of becoming the "first aid" cartridge to diagnose problematic MSX machines. It's not supposed to be reprogrammed on daily basis, only when a newer version of the diagnostics ROM appears. And being super cheap, it can be lying around until it's needed.

By Grauw

Enlighted (6262)

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02-11-2017, 13:41

But if you don’t have an EEPROM programmer (like most of us), isn’t a flash chip much cheaper than the cost of the programmer + the adapter board?

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