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Flash Chip Useable?
https://forums.nesdev.com/viewtopic.php?f=12&t=13471
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Author:  mleeneg [ Tue Nov 10, 2015 3:45 pm ]
Post subject:  Flash Chip Useable?

Hi all,
I just started out on the snes repro scene and read little things about what chips to get and while looking for the 29f032 I came across this chip S29GL032N90TFI040 without thinking I bought it and later found out that it was not a 29F032. Some major differences is that it is a TSOP-48 not a TSOP-40, it uses 3 volts instead of 5 volts and it can switch between 8-bit and 16-bit mode. I was wondering if I could still salvage this mishap and use it as a replacement for the 29F032 with a 3.3v regulator?

Author:  lidnariq [ Tue Nov 10, 2015 4:17 pm ]
Post subject:  Re: Flash Chip Useable?

Not by itself. Using a 3V IC on a 5V system will stress both the IC's overvoltage protection diodes and the SNES's address/data bus drivers.

In cartridges where they ignored this, I have heard very infrequent reports of crashing on specific systems, because the SNES expects CMOS signal levels (a logic 1 should be ≥4V), and the ROM is only emitting 3.3V.

For the address lines and control lines, you should add voltage translation or a voltage clamp. For the data lines, you should add a voltage translating bus transceiver.

Author:  mikejmoffitt [ Wed Nov 11, 2015 10:47 am ]
Post subject:  Re: Flash Chip Useable?

Given the rising prominence of 3.3V bootleg cartridges and less well-engineered flash / RAM carts, I wonder if building a middleman cart that just has the appropriate transceivers installed would be a helpful product.

Author:  mleeneg [ Wed Nov 11, 2015 2:42 pm ]
Post subject:  Re: Flash Chip Useable?

I was wondering if I should use a bi-directional level converter for an arduino for this purpose.

Author:  lidnariq [ Wed Nov 11, 2015 2:59 pm ]
Post subject:  Re: Flash Chip Useable?

You'll probably need a lot of them, but yes.

A voltage clamp (like the GTL2000) or unidirectional voltage translator (like a 74'16244) would be fine for all the address lines and control lines.

If you program the ROM before soldering, you can get away with a undirectional voltage translator for the data bus too; otherwise you'll need a bidirectional one like the 74lvc8t245.

Mind, the cheapest option per bit keeps on shifting. Checking on digikey right now, the cheapest option is the GTL2000 (4¢/bit) with the 74lvc8t245 at 6.5¢/bit... but those will probably change.

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