Confused about different SRAM chips

[Ace]

Soon, I'll be getting into collecting some arcade boards, but they're quite expensive, so when I stumbled upon this: http://www.raphnet.net/electronique/...p?section_id=0

I thought I'd give it a shot. This will convert an NES into a Nintendo VS. Unisystem arcade board minus the RGB PPU. Here's the problem - I'm stuck on this step: http://www.raphnet.net/electronique/...p?section_id=3

The NES I'm modifying for this project contains a Sharp LH5116DY-10 RAM chip for the PPU's RAM. I want to replace this with a Samsung KM6264BL-10 RAM chip salvaged from a dead Genesis Model 1. The problem is with the CE line. Here's the datasheet for the Sharp LH5116DY-10: http://www.datasheetcatalog.org/data...rp/mXqyqzu.pdf

And here's the datasheet for the Samsung KM6264BL-10: http://www.alldatasheet.com/datashee...G/KM6264B.html

Click the preview to see the datasheet.

The Sharp RAM chip has a single CE line, however the Samsung RAM chip has /CS1 and CS2, but no CE(CS is Chip Select). Which of these would correspond to the CE line on the Sharp RAM chip? 4K of the 8K of RAM in the Samsung chip is needed. Which of the two CS lines on the KM6264BL-10 do I need to solder to the CE line on the NES motherboard?

[tomaitheous]

/CS1, CS2 : Chip Select Input

/CS1 is chip select active low. CS2 doesn't have the bar, so I'd assume it's chip select active high. You shouldn't need to worry about CS2 from my guess (I have no idea what system uses that, but it's nice if you have a logic setup that outputs high for active and you don't want to use an extra inverter chip for that line).

Edit: Look at the 'FUNCTIONAL DESCRIPTION' table.

[TmEE]

Some chips have 2x CE lines, you can tie the active high signal permanently high... only thing you lose is deep power down mode (!CE high, CE low)..

[Ace]

Looking at the Genesis Model 1 motherboard, which is where I got the chip, CS2 appears to connected straight to the +5V line on the system. And /CS1 is connected to Ground through a surface-mount ceramic capacitor. On the NES motherboard, the CE line is not tied directly to Ground, but to some chip on the motherboard. Being as there's only 1 CE line, I would assume /CS1 is what will be tied to CE, and CS2 can be soldered to the NES' +5V line?

[tomaitheous]

Yes. Look at the 'FUNCTIONAL DESCRIPTION' table in the datasheet. Tie CS2 high. And make sure the PPU is asserting /CE not CE (it should be, but you never know).

[Ace]

The /CE line on the NES is actually provided by an inverted A13 signal generated by a hex inverter(chip U9 on the NES motherboard is a hex inverter), then passes through NES cartridges according to this page: http://www.raphnet.net/electronique/...p?section_id=7

I will be making custom VS. Unisystem cartridges for this NES > VS. Unisystem converted board, so I guess linking pins 57 and 58 on the cartridge slot is unnecessary?