ETROM / 256k SRAM problems. Need advice

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infidelity
Posts: 439
Joined: Fri Mar 01, 2013 4:46 am

Re: ETROM / 256k SRAM problems. Need advice

Post by infidelity » Thu Jan 12, 2017 4:29 pm

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.

baddflash
Posts: 13
Joined: Thu Jun 30, 2016 11:19 pm

Re: ETROM / 256k SRAM problems. Need advice

Post by baddflash » Sun Jan 29, 2017 12:57 am

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

lidnariq
Posts: 10435
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: ETROM / 256k SRAM problems. Need advice

Post by lidnariq » Sun Jan 29, 2017 11:22 am

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.

baddflash
Posts: 13
Joined: Thu Jun 30, 2016 11:19 pm

Re: ETROM / 256k SRAM problems. Need advice

Post by baddflash » Sun Jan 29, 2017 1:41 pm

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.

Yevgen.gr
Posts: 4
Joined: Sun Feb 21, 2021 10:24 pm

Re: ETROM / 256k SRAM problems. Need advice

Post by Yevgen.gr » Wed Mar 10, 2021 9:32 am

Sorry for necroposting.
I'm planning to do the legend of link repro for my collection and was also thinking on using 32k sram on etrom board.
So, isn't it sufficient to replace the battery backed-up sram chip with 32k one, wire A13 and A14 on it and permanently disable the non-battery backed-up one?
I just did not get why you're saying that pins 1 and 26 should be wired for both srams?

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