snes card 3v / 5v risk?

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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looping
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Re: snes card 3v / 5v risk?

Post by looping » Sun Dec 20, 2020 4:55 pm

ok i see the picture.
what would a good 5v to 3v conversion look like?
something that don't hurt the console

lidnariq
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Re: snes card 3v / 5v risk?

Post by lidnariq » Sun Dec 20, 2020 5:15 pm

Extra parts. At the very least, current limiting resistors, like has been seen on some of Krikzz's earlier flash carts.

Digital 5V outputs must be correctly "translated" down to 3V logic levels without putting an undue stress on the 5V side. This can be done with resistor-based voltage dividers, or "voltage clamps" like the GTL2000 parts, or explicit digital translation by 74x16245s.

Digital 3V outputs sometimes only have to be "protected": certain consoles can receive 3.3V as logic high reliably, such as the NES and Megadrive. For these, the 5V side just has to not be able to see the overvoltage protection diodes on the 3V side, and parts like the GTL2000 solve this. Other consoles, like the SNES and Game Boy, instead require full "translation" to make sure that when the 3V side says "high" the 5V side sees a different higher voltage that it understands to also mean "high" - for this, something like the 74x16245s are needed instead.

looping
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Re: snes card 3v / 5v risk?

Post by looping » Mon Dec 21, 2020 1:16 am

Thanks for the explanation :)

looping
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Re: snes card 3v / 5v risk?

Post by looping » Mon Dec 21, 2020 6:10 am

what can we think of this one?
it's SD2SNES

Image

lidnariq
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Re: snes card 3v / 5v risk?

Post by lidnariq » Mon Dec 21, 2020 12:12 pm

See those small long parts near the connector? That's what fixes it up and makes it ok.

looping
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Re: snes card 3v / 5v risk?

Post by looping » Mon Dec 21, 2020 1:13 pm

interesting...
it was probably my last question on the subject
Thanks again

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Fisher
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Re: snes card 3v / 5v risk?

Post by Fisher » Tue Dec 22, 2020 4:14 am

Oh yeah, that's a recurring subject that unfortunately many sellers who actually don't have proper knowledge try to sell as safe. I had a sort of horror history that I relate here.
I'm also not sure about Mega Drive's safety, as a friend supposedly had damaged one by intense use of a Chinese Everdrive clone.
Neither I'm willing to try some experiment on any of my beloved NES clones.

But I suggest that you don't simply throw the PCB away, a while ago, Krzysiobal and Ben Boldt were discussing the creation of an adapter to use safely these kind of games on the NES, maybe if you ask one of them he can make one SNES model for you for a reasonable price?

looping
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Re: snes card 3v / 5v risk?

Post by looping » Tue Dec 22, 2020 5:24 am

Hi Fisher
I will not use it in my snes
it's very sad that so many users use this kind of PCB without knowing what the problem is

about the MegaDrive, a new game has just been released: Paprium
http://paprium.com/
Are users of this game going to have the same problem?

Image

Image

Image

looping
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Re: snes card 3v / 5v risk?

Post by looping » Tue Dec 22, 2020 7:48 am

I just realized that the question is already discussed here:
http://forums.nesdev.com/viewtopic.php?f=9&t=21530

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aquasnake
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Re: snes card 3v / 5v risk?

Post by aquasnake » Wed Dec 23, 2020 2:02 am

Current limiting resistors are usually only suitable for:

1. Low speed signal;

2. The IO voltage drop is relatively small;

3. The bus bit width is relatively small;

For 5V/3.3V conversion, the current drawn on each resistor should be less than 5mA. So we choose 333ohm to reduce almost 1.7V. The total current consumption of 8-bit bidirectional data line is 40-50ma, while that of 16-bit bus may be as high as 100mA

However, the above restrictions are not satisfied in some cases: 1. If the frequency of the signal exceeds 10m, the signal will be attenuated, which will result in a wrong decision (oscillating several times near the threshold level). 2. Excessive IO will lead to increased power consumption and heating.

Therefore, low speed, low power consumption, less IO interface game cartridge, you can use resistor current limiting. But for FPGA cartridge, it is very difficult to use this solution, can only use level shifters.
Last edited by aquasnake on Wed Dec 23, 2020 6:53 am, edited 1 time in total.

looping
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Re: snes card 3v / 5v risk?

Post by looping » Wed Dec 23, 2020 3:33 am

hi aquasnake,
so the papirum PCB cannot be considered safe?

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aquasnake
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Re: snes card 3v / 5v risk?

Post by aquasnake » Wed Dec 23, 2020 6:03 am

looping wrote:
Wed Dec 23, 2020 3:33 am
hi aquasnake,
so the papirum PCB cannot be considered safe?
In an academic sense, most 3V carts are not very secure.

From a practical point of view, there are not a large number of complaints leading to hardware damage.

The prototype of Paprium seems to have used level shifters, so there should be no problem. The earlier Pier Solar also used resistors.

Kayumba
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Re: snes card 3v / 5v risk?

Post by Kayumba » Mon Apr 05, 2021 4:08 pm

aquasnake wrote:
Wed Dec 23, 2020 6:03 am
From a practical point of view, there are not a large number of complaints leading to hardware damage.
Maybe that is the reason why there is still so many existing repro with 3,3v without any «voltage translation»

Kayumba
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Re: snes card 3v / 5v risk?

Post by Kayumba » Wed Apr 07, 2021 6:37 am

Altera Max II EPM240T100C5N
For what that chip on boards ?

Kayumba
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Re: snes card 3v / 5v risk?

Post by Kayumba » Wed Apr 07, 2021 12:24 pm

lidnariq wrote:
Mon Dec 21, 2020 12:12 pm
See those small long parts near the connector? That's what fixes it up and makes it ok.
Do you know what chip is it?

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