Hi I recently made an add on board for laser invasion for sram (32k) and battery save and it’s not working I wired all traces from the ram to the ppu except we ce battery power vcc a13 and a14 to the mmc5 and it didn’t work I tried only on sim city the graphics are glitches up and it doesn’t save any idea where I went wrong?
Sim city expects 2 ram slots of 16K each, not a single 32K. Each slot is capable of 32K on its own so I'd suspect you have your single chip wired up wrong.
Ah I was thinking it may be something like that as I tried sim city in a famicom cart with two 8k and it worked hm any idea how to wire that? I may try to add jumpers or something I really wanted this to be an add on for any big mmc5 repro game like legend of link
Here’s how I wired it: pin 1-pin 70 mmc5(a14) pin 2-pin 4 prg pin 3- pin 5 prg pin 4- pin 6 prg pin 5- pin 7 prg etc. pin 14 an 22 (oe) ground.
Pin 28 to 56 mmc5(vcc)
Pin 57 mmc5 to battery positive through 1k resistor
Pin 71 mmc5 to pin 20 ram (ce)
Pin 69 mmc5 to pin 26 ram (a13)
Pin 76 to 27 ram (we)
May have found out the problem will check tomorrow I really want to get this going because the fit is great it will make for a clean add on to use a us full size cart for legend of link/ megaman/ any repro that needs mmc5
So I tried the fix: it was just I had traces not fully soldered but that didn’t help except that now on the pick map it’s all actual solid blocks before it was little pieces of blocks. The loading screen is fine but when starting a new town it’s all garbled. It did this when I just had the chips in board with no adapter so does this game mess up without sram? So am I leaving an address out or I don’t know any help with figuring this out would be appreciated I’m stumped here are some pics:
SimCity
specifically requires 2 x 8KiB of RAM. If you're using a single 32 KiB RAM, you'll need to hook it up to pins
75 and 93. Otherwise you get
some issues.
Ok thanks! So 75 and 93 go to where on the sram?
Well I connected 20 of the ram to 75 and it’s almost there the map shows well with just s row of corruption on top and it’s slmost playable but still won’t save. I just need to know where to wire 93 to
Well I have pin 20 (ce) of ram connected to 75 of mmc5(ce 1 and 2) and I tied a15 from the mmc5 high by wiring to the battery plus(too many wires to go anywhere else right now lol) and it works! BUT....doesn’t do the main thing I want it to do, save. So I’m wondering where I went wrong there I feel I’m almost there the game now works perfect just doesn’t save the whole reason for this adapter
Another strange thing to note: I tried various 5v points to use for pin 93 and the only one that works is if I wore straight to the battery positive anywhere else and the game glitches i don’t understand what’s going on
Please can someone tell me where to wire these signals? I tried every possible combo with 75 and 93 lidnariq you told me which signals but then left me hanging
I'm sorry, I just don't have the wherewithal right now to explain why, and I refuse to give answers without making sure they understand why first.
SimCity was made to run on ETROM, which has two RAMs. Without understanding more about how 1980s digital logic works, you should give up on trying to make it work with one RAM.
I have it working just need to know where to add these wires I have ce from the ram to t75 I know that’s right I just need 93 it seems tying it high it works I w don’t know your issue with further helping I’m NOT giving up till I succeed!
I will get this working so I can give people the option of using this instead of ruining an expensive koe cart with or without your help
You can graft two RAMs on top of the PRG ROM as easily as anything else. It's not like that rework is the hard part.
I made an adapter that solders onto the cart and doubles as the prg rewire and it’s just big enough for one ram chip
I’m wondering if it’s my battery circuit not working then game works but won’t save. Here is exactly how I have it wired:
Pin 56 of mmc5 goes to pin 28 of ram
Pin 57 goes to a 1k resistor to the batteries positive then to pin 28 of the ram
Pin 93 goes to pin 28 of ram
Frankym2612 wrote:
Pin 56 of mmc5 goes to pin 28 of ram
As far as I know, that's how the normal circuit works, that's fine.
Quote:
Pin 57 goes to a 1k resistor to the batteries positive then to pin 28 of the ram
But you already connected RAM Vcc to the supply on pin 56. Why did you connect it to the battery
also?
Quote:
Pin 93 goes to pin 28 of ram
Why did you do that?
For some reason if I don’t go from 57 to the battery and to the ram it glitches I tried just having 56 to 28, also the case with 93 I figured it needed to be tied high also tried tying it low it only works tied high
Frankym2612 wrote:
For some reason if I don’t go from 57 to the battery and to the ram it glitches I tried just having 56 to 28,
You've got some other problem going on then. The OEM carts aren't doing anything fancier.
Quote:
also the case with 93 I figured it needed to be tied high also tried tying it low it only works tied high
Why did you assume that pin 93 should be tied high or low?
I’ve definitely got something going on although using laser invasion 57 isn’t going to a ram like in the koe carts. For the 93 it is a15 and there is no a15 on the ram chip I figured it was high disable low enable there are no other accessible pins on the ram but maybe you could fill me in on where it goes? I assure you Ille understand
Frankym2612 wrote:
there is no a15 on the ram chip
You're right. There isn't.
The ETROM PCB ignores A13 and A14, and instead only uses PRG RAM 0 /CE and PRG RAM 1 /CE.
Ok so I’m guessing use pin 26?
Tell me what you're thinking. Why are you suggesting that?
You told me it needs to be connected to the ram
And I'm asking you to explain your thinking process.
I don’t need to explain myself to you either you help me or don’t get off your high horse and stop playing these games
I teach. I never give instructions that can be followed without thinking. If that doesn't work for you, have fun without me.
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
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
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.
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...?
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
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.
"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.
Thanks nocash I will check the voltages of the chip and here is a pic of my pcb thus far thanks for the help
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
Ehm, you have done things like measuring volts from pin 28 to pin 56? You must measure voltages between a given pin and GND.
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
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
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
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).
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.
Thanks, that makes it much clearer to know what have there. The wiring in the drawing looks okay.
I didn't see traces (drawn?) on the photo, but with the new drawing it's easier to understand what is shown on the photo.
mmc5.pin76+75 look misplaced in the drawing (but look okay on the photo, so it should be no problem).
mmc5.pin71 shouldn't be connected as you have only one ram chip.
The diode is gone now?
Though... there are MMC5 photos with SRAM in internet: Those seem to have a diode... between NES.5V and SRAM.VCC?
The resistor is really 1K? if it were 100K then you'd have a problem.
Probably obvious: I hope battery GND is also connected to sram+mmc5 GND.
The battery always has 3V, even when SRAM.VCC is less?
My main guess would be that SRAM VCC,/CE,/WE are accidently shortcut with other pins or with other chips.
Ya I removed the diode it didn’t make a difference. For the pcb I have extra pins because sim city calls for 2 8k ram chips and legend of link needs 1 32k pin 75 are 2 ram ce and 71 which I have on there is fit 1 ram ce. A short does make sense Ille have to keep looking and maybe redesign the board, how I have it drawn is how I have it wired now a little different then the pcb thanks for the help