SNES Multi cart using multi memory IC

I need some help. I've been trying to make a SNES multi cart using a M59PW1282 multi memory IC. It had the same pinout as a 27C322 except it has 44 pins instead of 42. Which I thought was great because I would hijack the top two address pins and run them to a 74Ls161 binary counter to do the rom select. The M59PW1282 is a 3v IC so I installed a voltage reducer. I also installed resistors on all of the address pins because they run around 4v each according to my multi meter. I've used the same wiring schematic as everyone uses to hook up a 27C322 , wiring it through the 257's. I don't have any issues there. When I wire in a 27C322 all works fine. But that only holds one rom.

The problem I am having is that , most of the time , only 2 of the Roms show up and when I can get all 4 of the Roms to show up it is sporadic and inconsistent.

Any one have any knowledge here?

Here is a link to the M59PW1282 datasheet.

http://pdf.datasheetcatalog.com/datashe ... d4023y.pdf




I can't figure it out.





If you need any other info just let me know.

And thank you in advance.

Sounds like you need a low pass filter on the reset/clock line to your counter. Reset line is pretty dirty and I'd guess it's clocking your counter multiple times, I've seen this issue in this application before. IIRC a 220pF and 1K did the trick.

Excuse my ignorance , but how exactly would I hook that up? Would the cap go from the 5v to the reset line on the counter ? Then a resistor go from the reset line to ground? I've heard of it before. But I've never hooked one up. Thanks again I advance.

Lowpass filter:

Thank you. I'll let you all know how it turns out.

Ideally, you actually want 2 resistors, a capacitor, and a Schmitt-triggered buffer like so:


The schematic shows an inverter, but a non-inverting buffer works just as well. Just be sure the input is a Schimitt trigger. Also, because you're dealing with an incoming reset signal rather than a switch, modify the diagram by removing the switch and attaching the reset signal to where the top of the switch was (between the two resistors).

I use 82K for R1, 18K for R2, and 100nF for C. A 74HC14 (or 74LVC1G14) works for the inverter, or '17 for a non-inverting buffer.

If a simple cap and resistor work just as well, what's the real benefit of all the extra components? That circuit makes sense in the application of debouncing a button in an application where a LPF won't work, but I don't see the point in this case.