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PostPosted: Tue Oct 03, 2017 1:29 pm 
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Joined: Wed Aug 21, 2013 5:00 pm
Posts: 19
Hello everyone. I'm building a 4 in 1 multicart right now. I know how to hijack the top two address pins of the prom and run it through a 74ls161 to switch between roms with the reset button. What I'm having trouble with is doing the same thing with the sram. I think I've assumed incorrectly thinking I could do the same thing by hijacking the rop two address pins. But that's not working for me. If anyone could give me some advice here I would great,y appreciate it.


I'm trying to use a 256k sram chip and split it into 4 , 64k banks.


And thank you in advance for your help.


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PostPosted: Tue Oct 03, 2017 1:43 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
Your assumption is basically correct. It's more likely some other mistake.


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PostPosted: Tue Oct 03, 2017 3:52 pm 
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Location: NE Indiana, USA (NTSC)
If the games don't use a battery, you don't need to bank the SRAM.

What mapper are we dealing with? MMC1, MMC3, or something else? Four battery-backed banks on an MMC1 might be tricky because it generates only +CE, requiring an inverter to turn it into /CE for the 256 kbit SRAM. The SXROM board has such an inverter.


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PostPosted: Tue Oct 03, 2017 4:32 pm 
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I'm working with mmc1. Battery backed sram. So , I'm correct in assuming that I can hijack the top two address pins just like the eprom?


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PostPosted: Tue Oct 03, 2017 4:33 pm 
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Yup.

When the 74'161 loses power, its output will fall to ground, but all the other address lines will also when the Nintendo is turned off. So that shouldn't be relevant.


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PostPosted: Thu Oct 05, 2017 10:24 am 
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Thank you. I’ll build it tonight. I appreciate the advice.


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