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PostPosted: Mon Jul 01, 2019 7:13 am 
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Well got it working now it’s saving so back to making hopefully the final revision then we’ll have battery save with a us full size cart that’s not a koei cart


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PostPosted: Sat Sep 07, 2019 8:12 pm 
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Well at a crossroads yet again with this sram addon board. Have it running sim city it works and saves but after 10-20 minutes it will erase the file. I put a fresh battery so I know that’s not it. I tried wiring it every way I could possibly think: from pin 56 (ram vcc) to pin 28 from 56 to battery with and without resistors most ways work with the same result. I have all pins running to the prg except 75 to ce on sram 93 to pin 26 sram and 76 to we on sram I don’t know why it wants to erase after a certain amount of time


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PostPosted: Mon Sep 09, 2019 11:36 pm 
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It’s odd sometimes the save will last 5 min, Sometimes 10, I’ve had it go an hr but it seems it will indefinitely erase but mostly it erases after pulling the cart out and reseating. Mostly one cycle and it will erase but sometimes two I don’t know why cycling the cart erases it also ive tried with a famicom cart and it saves perfect so it’s not the game.


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PostPosted: Tue Sep 10, 2019 5:35 am 
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Frankym2612 wrote:
Well at a crossroads yet again with this sram addon board. Have it running sim city it works and saves but after 10-20 minutes it will erase the file. I put a fresh battery so I know that’s not it. I tried wiring it every way I could possibly think: from pin 56 (ram vcc) to pin 28 from 56 to battery with and without resistors most ways work with the same result. I have all pins running to the prg except 75 to ce on sram 93 to pin 26 sram and 76 to we on sram I don’t know why it wants to erase after a certain amount of time

You have wired the battery to mmc5 pin56? There is a pinout description https://wiki.nesdev.com/w/index.php/MMC5_pinout saying that battery is pin57. Or is that the wrong pinout and you have other hardware? Or did you mean that you have wired the sram (not the battery) to pin56? That, yes, that would be correct. Maybe you could make a list/schematic showing what you have wired from where to where...?

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PostPosted: Tue Sep 10, 2019 2:49 pm 
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Sorry yes I meant pin 57 to battery that is how I originally wired it. I copied the real cart and went 56 to the sram through a .1uf bypass cap and I went from 57 through a 1k resistor to battery positive which then goes through a diode to the sram 28. I noticed that pin 57 is grounded and will not work till you lift it from the mmc5. I tried many variations of wiring: pin 57 to battery not connected to sram and connected, 56 to battery, battery to only 28 of sram, no diode, with diode, no resistor, you name it and I always get the same result. I did notice something weird that when going 57 to battery(even not connected to pin 28 of ram) and 56 to ram the voltage on the ram chip is lower than if I just go 56 to ram or 57 to battery


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PostPosted: Tue Sep 10, 2019 4:01 pm 
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Use a multimeter and verify that sram vcc is 3v, and sram /ce or /we must be also 3v (or ce2 must be 0v, if the sram chip has a ce2 pin).
If that voltages aren't there then you won't even need to try to connect the cart to the console.

I don't know what you mean with bypass cap, but you can't pass a supply voltage "through" a capacitor.
Passing the supply through a diode can work, if the diode is the right way around.
I don't know if the diode is needed, or if the chip already has that built-in, do you have a photo/link of a mmc5 cart with sram?

Your description is still a bit hard to follow, it would be easier if you would make a drawing or ascii arts showing which pin number & signal name on which chip goes through what components to which other pin number, pin name on which other chip.
Also, we are talking about "signals" and "supply voltages". It is a bit confusing when you say that "you" went through a resistor. Again, a drawing would be helpful to understand how you had accomplished that.

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Last edited by nocash on Tue Sep 10, 2019 4:06 pm, edited 1 time in total.

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PostPosted: Tue Sep 10, 2019 4:05 pm 
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"Bypass cap" usually means a 100 nF capacitor with its - lead on ground and its + lead on power, where the power pin is close to the IC's power pin. You put it in parallel with an IC's power and ground to even out voltage fluctuations caused by the IC's operation.

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PostPosted: Tue Sep 10, 2019 4:10 pm 
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Thanks nocash I will check the voltages of the chip and here is a pic of my pcb thus far thanks for the help


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17EC68B1-D729-4CBE-8B60-DF43458CEC9F.jpeg
17EC68B1-D729-4CBE-8B60-DF43458CEC9F.jpeg [ 2.71 MiB | Viewed 206 times ]
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PostPosted: Tue Sep 10, 2019 5:11 pm 
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How I have it configured now (pin 57 of mmc5 to a 1k resistor to battery not connected to ram and from 56 to the ram) I’m getting 0v from 56 to ram, 1.1v on ram 28 from anywhere else. we is showing 0v and ce is 0v. I have ce coming off pin 75 of mmc5(ce0 and ce1) and we coming off 76 of mmc5


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PostPosted: Tue Sep 10, 2019 6:03 pm 
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Ehm, you have done things like measuring volts from pin 28 to pin 56? You must measure voltages between a given pin and GND.

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PostPosted: Tue Sep 10, 2019 6:18 pm 
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Getting 1v from pin 56 and the sram I replaced the sram chip with a new one in case it was fried no difference we and ce still at 0v even measuring from ground


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PostPosted: Tue Sep 10, 2019 6:27 pm 
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When I remove my wire from 56 and just measure 56 I’m getting 2.78v put it back on the sram I’m getting 1.08. That’s with pin 57 attached to the bat if I remove 57 56 gets 0v


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PostPosted: Tue Sep 10, 2019 7:24 pm 
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When I check the koe cart I modeled it after ce we 56 and 57 all show 3.027v so something I’m doing is wrong but I can’t figure it


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PostPosted: Wed Sep 11, 2019 2:32 am 
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Frankym2612 wrote:
When I remove my wire from 56 and just measure 56 I’m getting 2.78v put it back on the sram I’m getting 1.08. That’s with pin 57 attached to the bat if I remove 57 56 gets 0v

That sounds as if pin56 connects to too many chips that draw too much current. Ie. as if your sram VCC connects to further points, like prg rom VCC, and chr rom VCC, or even to console VCC (if the console is attached to the cart).

On the other hand, if /CE and /WE are low, then the sram is in write mode and the sram may then draw too much current itself, that might also cause VCC to drop. Check that /CE and /WE are wired where?) to.
And make sure tha /CE and /WE aren't shortcut/wired to other places, like GND or prg rom /CE or whatever.

What is the problem about making a drawing? Do you have eye-sight problems or other disabilities that prevent you from using anything but text only? Even then, showing the wiring in ascii arts alike
"Chip X Pin WW (RAM./CE) --------------- Chip Y Pin XX (/CE)"
"Chip X Pin QQ (RAM./WE) --------------- Chip Y Pin YY (/WE)"
"etc."
shouldn't be too difficult (or well, if you are blind(?): the minuses are meant to form a line, representing the wire).

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PostPosted: Wed Sep 11, 2019 4:39 am 
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Ya Im blind that's how Im able to solder to a .65 pin pitch chip. I didn't make a drawing because I sent an attachment pic of my pcb with the traces on it(didn't you see it?) Here is a simple drawing for you of the pins from the mmc5 to the sram I couldn't make it any simpler.


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