(SNES)Help With Circuit for LoRom M27C322

[lidnariq]

Oh. I use an ICD3, but I know of people using PICKITs.

(In fact, it has to be programmed using HV programming: it uses /MCLR as a general purpose input.)

[LittleRain]

Ahh, lucky I asked, would not have realized that till its too late.
I guess ill stick with the 629 for now, my parallel programmer can't program that chip.
I'm currently designing a truly Universal programmer on the side, guess I'll wait until then.

Edit: Now that I think of it, I may be able to program it, and then set MCLR as IO. Which the programmer would then disconnect and never be able to be used again. I'll do that next revision though, I got a bunch of spare 629's anyways. I'll test with an 629 as well, as I can always unbrick it with my uni programmer.

[Kayumba]

Can I use this circuit ?
Will it works?
http://forums.nesdev.com/download/file. ... &mode=view

[LittleRain]

Battery will not work on that with most SRAM chips.
Use this one instead, I haven't tested the new battery circuit, but its the same one that the PoorStudent uses so there should be no problems.

[Kayumba]

Battery will not work on that with most SRAM chips.
Use this one instead, I haven't tested the new battery circuit, but its the same one that the PoorStudent uses so there should be no problems.
snes_32mb_lorom.png

OMG!
Thank you man !!!!!
Will try to combine it and add HiRom EPROM and 27C160 EPROM pins.

PS:
1- What DIODES do you use ? Will it work with DIODE-1N4148 ?
2- What is the transistor ? Is it 2N2222 ?
3- Why do you add switch with JUMPERS, what is those fonction ?

4- Where do I have to connect this Battery Net Port ?


It should be VCC (SNES), but across diode like here:


I dont see this diode on your schema.

Or maybe it's should make contact like that?


I maybe do some mistake, but I think, if you follow diagram of poorstudenthobbyist, it should be like that, no?

[lidnariq]

1- What DIODES do you use ? Will it work with DIODE-1N4148 ?

Low forward-voltage schottky diodes are better. It may work with 1N4148s, but you may also randomly lose the RAM contents.

4- Where do I have to connect this Battery Net Port ?

No-where. Vbat is a test point.

Or maybe it's should make contact like that?

No, the node you're looking for is "Vcc/2" which is already connected.

I maybe do some mistake, but I think, if you follow diagram of poorstudenthobbyist, it should be like that, no?

Doesn't matter. Current flows through both the resistor and diode, or flows through neither.

[Kayumba]

1- What DIODES do you use ? Will it work with DIODE-1N4148 ?

Low forward-voltage schottky diodes are better. It may work with 1N4148s, but you may also randomly lose the RAM contents.

4- Where do I have to connect this Battery Net Port ?

No-where. Vbat is a test point.

Or maybe it's should make contact like that?

No, the node you're looking for is "Vcc/2" which is already connected.

I maybe do some mistake, but I think, if you follow diagram of poorstudenthobbyist, it should be like that, no?

Doesn't matter. Current flows through both the resistor and diode, or flows through neither.

Thank you lidnariq

Low forward-voltage schottky diodes are better.

Can you give me link for reference, please.

I have at home only :
1N4001
1N4148
1N4007
Not sure if I can use one of them, without damage or loose some contents.

[lidnariq]

4001 and 4007 are even worse, with higher forward voltages. Won't damage anything, just may lose your saves.

Something like the BAT43 or BAT54 diodes are a reasonable place to start, but just search your favorite electronics supplier for "schottky diode".

[poorstudenthobbyist]

I've used 1N914s without issue for a while, which are pretty similar to 1N4148s. The current required to supply the SRAM data retention isn't too high (assuming you pick the right SRAM) so your forward voltage will be low.

That said, schottky diodes are generally better.

[Kayumba]

4001 and 4007 are even worse, with higher forward voltages. Won't damage anything, just may lose your saves.

Something like the BAT43 or BAT54 diodes are a reasonable place to start, but just search your favorite electronics supplier for "schottky diode".

Found BAT43 !
https://fr.aliexpress.com/item/3285411 ... eb201603_!

BAT54, all what I found is SOT23

[Kayumba]

I've used 1N914s without issue for a while, which are pretty similar to 1N4148s. The current required to supply the SRAM data retention isn't too high (assuming you pick the right SRAM) so your forward voltage will be low.

That said, schottky diodes are generally better.

Ok.
So...schottky BAT43 !
They are pretty cool. I like the color.


I'am surprise cause schottky BAT43 it's 30V (Peak voltage), is that LOW ?!
1N914s -> 100V (Peak voltage)
1N4148s -> 100V (Peak voltage)

The current required to supply the SRAM data retention isn't too high (assuming you pick the right SRAM) so your forward voltage will be low.

All kind of SRAM that I have is OK :

BR6216B 10LL -> Single +5 V supply
HM6264ALP-10 -> Single +5 V supply
HM62256BLP-10 -> -0,5 to 7,0 V supply

[lidnariq]

I'am surprise cause schottky BAT43 it's 30V (Peak voltage), is that LOW ?!

Not really. They're specifically designed for low forward voltages, and the reverse voltage isn't a parameter that they care about. In this case, they shouldn't be seeing more than 5V reverse voltage anyway.

All kind of SRAM that I have is OK :

For this purpose, what you care about is the line in the datasheet that says "minimum voltage for retention", not the operating voltage.

[Kayumba]

"minimum voltage for retention"

I dont find that.

"Standby Voltage-Min" Is that the same?

Or "Supply Voltage-Min (Vsup)"

If in datasheet I dont find "minimum voltage for retention", that’s mean that they does not have a separate RAM retention voltage.
So in this case, the minimum voltage for RAM retention is the normal minimum Vcc voltage, exact?

BR6216B 10LL -> Supply Voltage-Min (Vsup) : 4,5
HM6264ALP-10 -> Min Supply voltage : 4.5
HM62256BLP-10 -> Min Supply voltage : 4.5

[lidnariq]

"Standby Voltage-Min" Is that the same?

Yes, probably.

HM6264ALP-10 -> Min Supply voltage : 4.5

For both Hitachi parts, look at the page "Low Vcc Data Retention", where the line is given:
"Vcc for data retention Vdr min: 2.0V"

For the Rohm part, the words "Can maintain information at voltages as low as 2 V" on the front page, or "Data holding characteristics at low voltage", "Voltage required to hold data" is the important bit.

[poorstudenthobbyist]

You also should check to see if the data retention or standby current is low as well. The lower it is, the longer your game will save. Generally -L or -LL parts have low currents for save retention.

Coin cell batteries are rated for ~220mAh, so if you divide the amp-hour rating by the retention current, you'll get a rough estimate of how long the battery will last.