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Hello.
Sometime ago, I remember to have read something about implementing a UxROM solely with an 74'373, some resistors and 2 transistors.
I've tried some crazy configurations, but none worked.
Could someone please explain, or better, draw me some schematics to make it easier for me to understand?
Thanks in advance!

If you take the original UxROM image, and divide it into 16 KiB slices (let's call them "0" through "7"), and reassemble those 16 KiB slices in this specific order: 0717273747576777
And then burn it onto a BNROM-class cartridge. In this way, you can convert a 256 KiB BNROM board into a 128 KiB UNROM without any rewiring.

Cool!!
Great hacking info! Thanks!!
But what I want to do is to use an 74'373 instead of a 74'161, mainly bacause 74'373s are easier for me to get.
Maybe using it together with the 74'32 would be a option, but I fear to end with a board as messier as this one I've built yesterday:




I've felt just like Dr. Frankenstein, and screamed: It's alive!! It's alive!!
I should already know that most of the time good looking != functional



Well... a little bit less components on the junk pile, and lots of fun for me and my daughters!
I even patched it with the infinite lives code. I bet that even my 5yr old can finish this game!!

The 74373 is a 3-state latch that outputs the bank number only when /OE (pin 1) is low. Tie /OE to A14, and tie Q0-3 high through resistors of appropriate value. Then I think the transistors are to calculate the latch's active high write enable: LE (pin 11) = /ROMSEL NOR R/W

Source: NXP 74HC373 data sheet

Oh, right, specifically the 74'373. The NES can interface with a 74'377 without any extra parts, but to use a '373 you'll have to generate the +LATCH pulse.

So you want something that is high only while /ROMSEL is low and R/W is low. Sounds like a NOR gate?

What kind of transistors do you have? I guess you could be silly and just build a (needlessly complicated) full TTL NOR gate: http://www.allaboutcircuits.com/textboo ... -or-gates/

Transistor Gates has the schematic of a NOR gate with two transistors and three resistors, as well as the schematic of a NOR gate with one transistor and three resistors.

Bonus: You may be able to run this latch enable signal to your flash memory's /OE (with /ROMSEL itself on /CE) and prevent bus conflicts.

Thanks!!
Great info!!
You guys are great!
I'll try this tomorrow and see what I can get.

What values should I try for the resistors? 10k maybe? Or it's too high?
Looks like I'll have lots of experiments to do this holiday!!