SNES->Cart Voltage Observation

I plugged in a cart to my SNES without the Casing, and used a multimeter to measure the Voltage of VCC->Ground on the cart. I got a value of 3.05 volts on mine. Does this mean that I can use a 2.7 V ~ 3.6 V flash memory on my cartridge? Or must I stick to 5 volts?

The reason why I ask this is because I will be using an FX2LP chip, which takes USB power at 5V, regulates to 3 volts for itself. I'm at the point where I imagine can I just use that regulated 3.3v for everything? Or do I have to figure out a way to drive 5v to some places.

That's it! TY Baby.

The original SNES runs at 5v, so your either not measuring Vcc to GND, or you have a clone.

i am pretty sure mine unit is legit (at the least). see Voltage Change on this page: http://digitalfantasy.angelfire.com/sne ... tions.html

I basically put my multimeter on the + and - terminals of the SRAM battery while plugged into SNES. Hm the battery says 3V. hmm lol I wonder if that makes my measurement inaccurate to actual SNES voltage. How to accurately measure the 5v??

Alright I admit to being dingus. I plugged multimeter direct into Cart slot. and 4.77 V

The SRAM isn't powered from Vcc. So my original statement holds that you didn't measure Vcc to GND.

The battery is a different voltage that is lower as you don't need 5V to preserve SRAM contents. Also the actual voltage will differ depending on the load some. The SNES is indeed a 5V system. You can use a 3.3v flash chip directly possibly but you could cause hardware damage. You should use all the proper voltage level translation to avoid glitches or hardware damage.

Now the FX2 chip I plan on using to do the flash io says it has 3.3 V operation with 5 V tolerant inputs. I need to learn what this means so I can interface it to 5V environment. I'm not even sure if it is possible to do what I want. MEH

I found this for interfacing between 3V to 5V environment. It's talking about 3V can drive TTL switching levels, but not CMOS. Is the SNES cart working CMOS or TTL (there are solutions for CMOS if necessary).

http://ics.nxp.com/support/documents/lo ... /an240.pdf

According to viewtopic.php?f=12&t=10145

SNES uses TTL logic. Hip Hip Hooray

It means that you need to supply the chip with 3.3v power, and it will output 3v signals. But it's safe to apply 5v signals to it's inputs. Most 3v chips aren't safe to apply 5v signals to the inputs, but since this one is, you're good. The only other concern is will your 5v chips you're interfacing with accept a 3v signal as a logic high. Generally the answer to that question is yes, so you should be good.

Is it a lot more expensive to manufacture a 3.3 V IC that's 5 V tolerant? Or is it just that it adds a few pennies to the cost of a part with slim margins for a feature that only a niche community will use?

so if my Flash chip Datasheet ( http://download.siliconexpert.com/pdfs/ ... 25022a.pdf ) says it's CMOS. Does that mean I need to forget about the rest being TTL, as if it doesn't apply? And then get "Philips Semiconductors developed special dual VCC levelshifters to address that situation (see Section 6.0)." as referenced by http://ics.nxp.com/support/documents/lo ... /an240.pdf

Or can I.. not do that. And just treat it normally?

Actually, under features for that chip, it does say TTL I/O Compatibility. Whatever that means.

You're probably good, in my experience your major concern needs to be level compatibility and less concern for logic type. I've yet to see issues due to logic family, but it's a possible source of issue with old/new hardware. But you can probably ignore it and not worry too much...

I think it's the latter.

Both ways you most likely want overvoltage protection to help protect against electrostatic discharge. For 3.3V parts that aren't 5V tolerant, the pins almost all just have a pair of schottky diodes from ground to pin and from pin to vcc, so that more than one diode drop above or below the rails are dumped onto the rails. A 5V-tolerant part, on the other hand, has to either forsake ESD protection, or must use a bunch of zener/avalanche diodes to protect all the pins instead.

It also requires larger input buffers to handle the higher input voltages, which equates to larger die size and cost.

The voltages get lower as the wafer die sizes get smaller, so it's a byproduct of the ever-shrinking manufacturing process that newer, 3v chips cannot handle higher voltages. Physics is a real jerk.

The real push for lower operating voltages is power consumption now-a-days. Once the lower voltages are supported the transistor size of the next device series is subsequently reduced. But yes, physics still calls the shots.

Doing some research and I need to clarify one thing here. So my USB-powered device will be taking the 5 Volts from the USB bus and using a 3.3v regulator, I send the 3.3v that it needs. However, there is a flash chip I already designed an adaptor for to fit into the SNES mask rom pinout. This flash chip operates at 5V. To get this all working correctly, I will be sending out the 5V to the SNES Cart Connector, and that will give my chip the 5V to its VCC, even tho the main USB device(the 'flasher') will be operating at 3.3V. And since the flash chip is TTL I/O capable, and the 3.3v chip has 5V tolerant inputs, everything should work great between them on the I/O lines. My main concern here is making sure that I can connect the Cart connector to 5V, and won't experience any issues having my mcu chip running at 3.3v.

Reviewing this sounds perfect. Since I am an electronics noobie, I am posting this for clarifications from the experts. Thanks guys. Bazz

Just as long as it's 5V tolerant, you're good. If you're plugging the USB cable in while it's connected to the SNES though you'll want to devise a method of switching/auctioneering between the USB 5v and SNES 5v. I wouldn't suggest tying the two supplies together directly. I've heard the SNES regulator may not care though, who knows about your USB port though.

From the FX2LP datasheet:



So, that's a problem.

Sounds like it, but is that saying the 3.3v part is 3.3v tolerant? Doesn't make much sense unless we're talking about different parts here.

This page seems to disagree: http://sigrok.org/wiki/Lcsoft_Mini_Boar ... Extensions

Yeah, that must've been a different part because this datasheet states



so nevermind.