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ETROM / 256k SRAM problems. Need advice
http://forums.nesdev.com/viewtopic.php?f=28&t=15077
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Author:  infidelity [ Thu Jan 12, 2017 4:29 pm ]
Post subject:  Re: ETROM / 256k SRAM problems. Need advice

Final version of Legend of Link. Now working correctly on MMC5 boards with 32kb SRAM.

http://acmlm.kafuka.org/uploader/get.php?id=5155

My issue all along, was that I wasn't wiping the SRAM. I though by default the $6000-$7FFF region was always 00's, because that's how the FCEUX debugger displays that region. I was performing checks of certain registers, seeing if they were not equal, (set by the player) but what was happening, was by default when first running the game on a wiped SRAM chip, the specific regions being checked were filled with FF's, so my game was doing it's SRAM preparations properly, resulting in the real hardware issues.

All fixed, been confirmed on both the Famicom & Nintendo systems.

Author:  baddflash [ Sun Jan 29, 2017 12:57 am ]
Post subject:  Re: ETROM / 256k SRAM problems. Need advice

I'm working on this right now using a FC etrom board. The game works just fine but it will not save. After reading the game now required a 32kB sram I initially tried swapping wram-0 ( battery backed sram) , than wram-1 as well (I pulled the sram chips from snes carts.) I tried swapping battery power from wram-0 to wram-1 also. I've installed a new battery and confirmed voltage at the sram. Finally I thought to check if it remained after a reset and no that doesn't work either. Not sure what I am missing, but it appears to not be saving at all. There are no CL15/SL15 pads on the FC board so not sure if that matters or if there is some fc equivalent that needs to be changed.
No idea where to go from here other than trying different roms.
Any help greatly appreciated.

Thanks

Author:  lidnariq [ Sun Jan 29, 2017 11:22 am ]
Post subject:  Re: ETROM / 256k SRAM problems. Need advice

HVC-ETROM needs a little bit of rework in order to work. The wiki's documented solder jumper is only sufficient for NES-ETROM.

See what I said here. TL;DR: You'll need to rework both RAMs' pins 1 and 26.

Author:  baddflash [ Sun Jan 29, 2017 1:41 pm ]
Post subject:  Re: ETROM / 256k SRAM problems. Need advice

Thanks I found that post earlier and its working well now. I guess if I had bothered to check the datasheets for the sram I would have found that issue earlier,lol.

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