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how to execute some code on nes ?
http://forums.nesdev.com/viewtopic.php?f=9&t=12511
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Author:  rus084 [ Mon Mar 16, 2015 11:50 pm ]
Post subject:  how to execute some code on nes ?

hi everybody ! i'm new on this forum .

i have clone of nes "dendy" and want to execute some code .

i have 27c512 (uv erasing eprom) and stm32f4discovery (arm cortex m4@168mhz , 1m rom , 192kb ram , much gpios )

i make rom via cc65 compiler (its not using ppu , only sound controller) and make c array from it .

how i can do it?

Author:  lidnariq [ Tue Mar 17, 2015 12:09 am ]
Post subject:  Re: how to execute some code on nes ?

For you own sanity, please get an EEPROM (28c, 29f, 39f, 49f, &c). UVEPROMs (such as the 27c512) require special equipment to erase, or at least several days outdoors with the window pointing at the sun; as well as multiple different voltages to program.

After that, building your own EEPROM programmer is straightforward; the datasheet for the EEPROM will give you specific instructions on how to program the data into the EEPROM.

Finally, you will need to remove the ROM from an existing cartridge, possibly rewire some signals depending on the cartridge you're starting with, solder in a socket, and put your own EEPROM into that socket.

Author:  tepples [ Tue Mar 17, 2015 8:13 am ]
Post subject:  Re: how to execute some code on nes ?

Normally I'd agree and say use flash EEPROMs.

But there are probably some edge cases where one can find large quantities of pulled UVEPROMs and a regulator to make the programming voltage for far cheaper than new flash. Google eprom eraser brought me this $20 device that erases an EPROM in 10 minutes.

Author:  rus084 [ Tue Mar 17, 2015 9:22 am ]
Post subject:  Re: how to execute some code on nes ?

i dont think what erasing is hard . i think about programming .
my discovery board is 3v logic .
27c512 never output on adress wires?

on 27c512 writed 80486 isa bios rom , have this data some value ?

Author:  lidnariq [ Tue Mar 17, 2015 12:11 pm ]
Post subject:  Re: how to execute some code on nes ?

rus084 wrote:
my discovery board is 3v logic.
That may or may not work, but at least you can find out by just trying to read from the ROM. Is the discovery board 5V tolerant?

The specific voltages you'll need will depend on who made your UVEPROM, but you'll probably need ~5V and ~12V. I have no idea what would happen if you provide too low of Vdd when programming... probably nothing good.
Quote:
27c512 never output on adress wires?
Correct, the only output are the data lines.
Quote:
on 27c512 writed 80486 isa bios rom , have this data some value ?
Seems unlikely, but reading it before erasure would let you verify most of your wiring on the programmer.

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