Mother repro using TN-ROM board

Mother repro using TN-ROM board
by DNSDies on 2012-06-02 (#94940)

Ok, I pretty much understand how to do this after researching, but I'd just like to confirm this information with the veterans here.

I understand that Mother can be reproduced using TK-Rom boards, but I'm just plain unwilling to give up my copy of Deja Vu.
As I understand it, a TN-ROM is suitable except for the lack of a battery to power the WRAM when the system is off.

What I have is a copy of Tetris 2 I'm willing to offer up as a sacrifice, and a ready supply of diodes, capacitors, resistors, and batteries.

After doing some research and tracing the paths from my copy of Deja Vu, here's what I've come up with:

Code:

Adding Battery backup to TN-ROM boards:

Supplies Needed:
2 Diodes (lowest forward voltage)
1 1kiloohm resistor
1 2.2uf 5volt electrolytic capacitor

1) Clip pin 28 on WRAM, solder 2 separate wires to hole 28 and pin 28.
2) BATTERY POSITIVE - solder to DIODE (clear end), (DIODE banded end) to RESISTOR; RESISTOR to CAPACITOR POSITIVE --AND-- to WRAM Pin 28 -END-
3) 5V (hole 28's wire) to DIODE (clear end), DIODE (banded end) to WRAM Pin 28' wire
4) Solder BATTERY NEGATIVE to CAPACITOR NEGATIVE

Is this how it is supposed to work?
I understand the concept and what each part does (diodes block system 5v from exploding the battery, or making the battery power the cart, capacitor smooths the transition between system power and battery, and resistors act as voltage magnets).

from what I can see on my copy of Tetris 2, Wram pin 1 has no connection (maybe I can have battery in on pin 1 and leave system voltage on 28 without clipping pins?), and there is already a 2.2uf capacitor on board to the left of the MMC3C (negative connects to ground, positive to 5v).

Can I simplify this by using parts already on the board?

by DNSDies on 2012-06-07 (#95177)

so, no advice on this?

by infiniteneslives on 2012-06-07 (#95181)

DNSDies wrote:
so, no advice on this?

If you look around you'll notice we're not here to help you make repros for numerous reasons.

by DNSDies on 2012-06-08 (#95224)

right, except for the fact this isn't really a repro, since Mother was never released in America.

If I wanted to make money, I'd be using donor boards that didn't require $5 in parts.

This is just for me, I have no intent of selling it.

You don't seem to have any problem with other reproductions on this board.
I can see at least 5 threads on page 1.

by infiniteneslives on 2012-06-08 (#95230)

These threads just get old. If you're looking for help on a schematic your best bet is to draw it up for yourself and post it asking for feedback. People continually pop in and ask "How do I make a copy of X game for X reason?"

Your basically asking someone to explain the entire process for you. I don't know how to answer your question other than do all the reasearch myself on the differences between the two boards and create a schematic for you and then tell you how to assemble everything. I nor anyone else is likely to get any enjoyment out of doing all that leg work for you.

My suggestion: Research. Draw a schematic. Assemble it. Troubleshoot. Play.

by DNSDies on 2012-06-09 (#95237)

Except I'm NOT asking for someone to explain it to me, READ --THEN--- RESPOND.

I already have my plan posted above, I already explained that I know HOW it works and WHY it works.

I just want a simple "yes" or "no" from someone who has already done this, and if I can use the capacitor already on the board.

did I get it right? if so, cool.
if not, I'll go back to doing my own research like I did in the first place.

I know it will save data and keep the WRAM safe, but will it last as long as a normal cart, or did I screw up the wiring and cause the battery to drain too fast? I can't test that any way besides running the console for hours.

Here's the damned schematic.

by infiniteneslives on 2012-06-09 (#95238)

Your schematic is fine.

I wouldn't reuse the cap on the board because you still need that cap for the other ROMs on the board.

by HardWareMan on 2012-06-09 (#95257)

You forgot a 10k pullup resistor for CS and WE.

by DNSDies on 2012-06-10 (#95264)

is that necessary?
It's the first I've heard of needing another resistor.

This is for the /ce pin on the wram right?
Why does that need a resistor?

by tepples on 2012-06-10 (#95267)

My guess is that it helps ensure that the voltage on that signal is well defined even while the Control Deck is powering on or off.

by HardWareMan on 2012-06-10 (#95268)

tepples wrote:
My guess is that it helps ensure that the voltage on that signal is well defined even while the Control Deck is powering on or off.

Exactly. If you don't pullup these signals to backup power, your data can be corrupted. To be honest, you must build this schematic:

Or use some specific IC, for example BA6162:

And your data will be saved for years. I have Light Crusider cartrige for Megadrive and save files are works after 5 years from last use.

by infiniteneslives on 2012-06-10 (#95275)

HardWareMan wrote:
And your data will be saved for years. I have Light Crusider cartrige for Megadrive and save files are works after 5 years from last use.

While that circuit is probably drastically better than the original circuit most people don't have issues with the original one provided you do put the pull ups/downs on /CE(CE) respectively like you pointed out.

One thing is your circuit doesn't affect the lifetime of save data in regards to years. It protects it when inserting/removing and power on/off the cartridge which is where most problems arise. But the lifetime (years) a that the data will be maintained mostly depends on the static power consumption of whichever SRAM you choose, and the shelf life and quality of the battery.

I've had data maintained with Nintendo's standard battery backing last from when I played as a kid nearly 20 years ago.

by HardWareMan on 2012-06-10 (#95311)

infiniteneslives wrote:
One thing is your circuit doesn't affect the lifetime of save data in regards to years. It protects it when inserting/removing and power on/off the cartridge which is where most problems arise. But the lifetime (years) a that the data will be maintained mostly depends on the static power consumption of whichever SRAM you choose, and the shelf life and quality of the battery.

Exactly. But we assume that SRAM is a low power one and battery is good one, isn't it?

by infiniteneslives on 2012-06-10 (#95313)

HardWareMan wrote:
Exactly. But we assume that SRAM is a low power one and battery is good one, isn't it?

Assume what you'd like, but there are lots of SRAM's that don't have low static power. There are also lots of dead/cheap batteries in the world. It depends on what you choose...

by HardWareMan on 2012-06-11 (#95322)

infiniteneslives wrote:
HardWareMan wrote:
Exactly. But we assume that SRAM is a low power one and battery is good one, isn't it?

Assume what you'd like, but there are lots of SRAM's that don't have low static power. There are also lots of dead/cheap batteries in the world. It depends on what you choose...

OK, you win.

by DNSDies on 2012-06-11 (#95370)

so, pulldown resistors on we and ce of the sram to ground ensures those lines stay tied to ground when powering on or off the console.

I suppose this makes it so you don't have to hold Reset when powering off?

It needs to be a 10kohm resistor?
I have a spare 1kohm, but I'd have to o buy a 10kohm.

by infiniteneslives on 2012-06-11 (#95375)

You want to pull down active high signals (CE)

And pull up active low signals (/CE)

You shouldn't have to deal with /WE

Don't remember what the original boards do but I think they always ground /CE and then control CE by the mapper. So you'd do similarly and only pull down the CE line.

I think they used 10K but 1K will probably work as well.

And technically since you're coping Nintendo's design it doesn't buy you out of holding reset. Although you don't have to hold if if you feel lucky...

by DNSDies on 2012-06-12 (#95426)

Alright, sounds cool.

I'll draw up a pretty schematic for free reference.
This battery thing seems to be a fairly common question and even with 2 days of searching I still couldn't find all the information I needed, so it might help to have a standard reference document in one place.

Do you guys have a wiki or something I could upload it to?

by tepples on 2012-06-12 (#95433)

DNSDies wrote:
Do you guys have a wiki or something I could upload it to?

We have a wiki, but due to past abuse, I'll need to create an account for you. Just PM me the username you want to use and an e-mail address for you to get your password.

by l_oliveira on 2012-06-13 (#95471)

Adding to what HardWareman posted, look at the BA6162 chip in special, it has two chip enables, one inverted and one non inverted.

While non inverted signal is obviously meant to be used with chips that have a additional non inverted chip select pin such as 6264 or 628128, you can use chips that only have a single inverted chip enable signal such as 62256 or 628512 with it if you do this:

Code:
R/W---\
|LS32>----- SRAM /WR
/CE---/
/CE----\
|LS32>----- SRAM /OE
GND---/

Where R/W is the write strobe from the mapper or NES, where appropriated. /CE is the original chip enable strobe that would go to the SRAM chip and places it on the bus when active. This circuit frees the original SRAM /CE which will be then used to control the SRAM data integrity and switch it into low power mode when power is off.

Don't forget to have the SRAM /CE go straight to the inverted /CE output on the BA6162 chip.