Could someone explain these terms?

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IIMarckus
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Could someone explain these terms?

Postby IIMarckus » Sat Mar 15, 2008 5:10 am UTC

I dunno if this forum is for electronics in general or just computer hardware, but I'll try anyway. :?

It turns out one of my old GameBoy cartridges didn't have a screw in the back, so I took it apart to look at the insides. I'm just wondering if someone could explain what some of it might mean, like

- C1 [symbol] 103, C2 [symbol] 103
- CLI 26A
- C3 10mu
- R1 resists 10K (also why is this resistor labeled R1 and the others labeled C1/C2?)
- the symbols to the left of C3
- the thing labeled 6129 3A96
- VDD and GND
- Are U1/U2/C1/C2/R1/etc standard terms in electronics and if so, what do they stand for?

Thanks for your time, I'm really clueless when it comes to this kind of stuff

Micron
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Re: Could someone explain these terms?

Postby Micron » Sat Mar 15, 2008 6:29 am UTC

I can answer some of your questions but I suspect the answers will do you little good. If you want to get started playing with electronics there is some good advice in other sections of these forums. An integrated circuit like the one you are looking at is difficult for a beginner to work with and it is unlikely there is anything you can do to modify it.

VDD and GND are standard labels for the voltage supply and ground connections.

Components on a PCB (printed circuit board) are usually labeled however each manufacturer can use their own style so the meanings are not always consistent. It is pretty standard to label a resistor a "R{number of the resistor}{value of the resistor}". For example your PCB contains a label "R1" meaning the first resistor on the board, followed by the standard symbol for a resistor, followed by the value of the resistor; "10k" (10,000 ohms).
Similarly capacitors are often labeled starting with "C{number}", diodes with "D{number}", integrated circuits with "U{number}", and so on. Your board contains three integrated circuits labeled "U1" through "U3". The labels next to each circuit usually identify the model placed in that socket (note that the "MBC2A" next to "U2" matched the model number of the corresponding IC).
"C1" and "C2" probably refer to capacitors on this board (103 micro-farad capacitors in this case). Here they have been replaced with resistors because a resistor will behave like a capacitor to high frequency signals and it is cheaper to use a resistor when possible.

The labels on each integrated circuit (the black rectangles) usually identify the manufacturer, model, and possible a serial number. Again the format used will vary between manufacturers. An original GameBoy cartridge is old enough that you may no longer be able to find those part numbers in a catalog to identify them.
In your case the "MCB2A" is probably the "memory bank controller" which allows the GameBoy to read the game's data. U1 is labeled "PRG", short for "programmable" and is probably the ROM for the game. (See here).
Without knowing more about the board I can't say what the "6129" component is, the label just doesn't provide enough information since I don't know the manufacturer or anything else.

I'm afraid that from your picture I can't see the last symbol well enough to identify it for sure. It might label the negative terminal next to it as a ground but I make no promises.

In any case that should give you a general idea what each of those parts does. Now what can you do with it knowing that information? Not much. You don't have the tools to read the game memory and a ROM chip like that is not designed to be rewritten so you couldn't easily modify it even if you had the right equipment. You're also looking at something that is accessed rather quickly (I think a GameBoy used a 6 or 8 MHz clock), much faster than you can hope to examine without some additional hardware to capture memory accesses and such.
If you want to play around with hardware or learn to write games of comparable complexity to a GameBoy game those are both possible but I do not think that the cartridge you are holding will help with either one.

Hope that was of some help.

LikwidCirkel
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Re: Could someone explain these terms?

Postby LikwidCirkel » Sat Mar 15, 2008 7:29 pm UTC

Micron wrote:103 micro-farad capacitors in this case

You post seems correct except for that. That value would indicate a 10,000pF capacitor. For R and C values the third digit is a decade multiplier for the first two. It essentially just indicates how many zeros to add to the first two digits to determine the value.
With resistors, it's in ohms, and capacitors, usually pF. Micro-Farad values are a little different, and might have notations like 0u1 for 0.1 micro-Farads. The value above that says 10mu for a capacitor could be 10 micro-Farads. The would have to be a larger electrolytic cap for that value, and the size of the capacitor is usually helpful for making educated guesses on the value-labelling system.

IIMarckus
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Re: Could someone explain these terms?

Postby IIMarckus » Sun Mar 16, 2008 2:29 am UTC

I have been enlightened. Thank you very much! :bow:
Micron wrote:"C1" and "C2" probably refer to capacitors on this board (103 micro-farad capacitors in this case). Here they have been replaced with resistors because a resistor will behave like a capacitor to high frequency signals and it is cheaper to use a resistor when possible.
Capacitors store up electricity and then discharge it, right? I can see how a resistor could mimic that if a capacitor would have been filling up very fast.
Micron wrote:integrated circuit (the black rectangles)
Is calling them "chips" in any way correct?
Micron wrote:In your case the "MCB2A" is probably the "memory bank controller" which allows the GameBoy to read the game's data.
Yes, the GB has only 8k of RAM for the program, and the MBC2 can let it handle up to 256 through banking. Later, the MBC5 allowed for up to 2 MiB.
Micron wrote:Without knowing more about the board I can't say what the "6129" component is, the label just doesn't provide enough information since I don't know the manufacturer or anything else.
Could it be to prevent SRAM from corrupting during reads and writes? I read something about that once.
Micron wrote:Now what can you do with it knowing that information? Not much.
Yeah, mostly I wanted to know what they meant; thanks for filling me in. I'll admit I don't "get it" all yet, but I'll save this thread and maybe research the subjects. I've done some GB programming before (and actually know how to account for MBCs in software), which is partly what interested me in this.
Micron wrote:Hope that was of some help.
It really was, thanks.

Thank you too, LikwidCirkel. The "103 -> 10000" notation is definitely something I'll keep in mind.

Micron
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Re: Could someone explain these terms?

Postby Micron » Sun Mar 16, 2008 7:44 am UTC

LikwidCirkel wrote:You post seems correct except for that. That value would indicate a 10,000pF capacitor.


Oops. Well that's what I get for posting in the middle of the night.

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MFHodge
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Re: Could someone explain these terms?

Postby MFHodge » Tue Mar 18, 2008 9:26 pm UTC

IIMarckus wrote:
Micron wrote:integrated circuit (the black rectangles)
Is calling them "chips" in any way correct?

There's nothing wrong with calling an IC a chip, but resistors and capacitors can be chips also, especially on surface mount PCBs.
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mosc
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Re: Could someone explain these terms?

Postby mosc » Wed Mar 19, 2008 7:33 pm UTC

This whole thread is mostly dis-information. C does not always stand for capacitor. It's sometimes component or perhaps labeling a signal path or a billion other things. As for the "can see how a resistor could mimic that if a capacitor would have been filling up very fast." I had to laugh. There's a nugget of truth under there because any component is not ideal and will have some various capacitances between nodes but for god's sakes man. It's a resistor plain and simple.

Most of the notation on the PCB is intended to mean something to testers. The little round wholes are for inserting test probes to observe the signal on that path. For example, "GND" is almost always labeled somewhere (as it is here) and is used as the reference connection for the test probes.

As for what components are on the board? Clearly there are 7. Three IC's, three resistors, and a battery. The three ICs are a little bit harder to judge but i'd wager that the MCB2A is a bus chip meaning it does the proprietary magic of converting the console's pins and matching it to the cartridge. Nintendo makes it and closely guards it's function. People do make counterfit cartridges remember but most of em have these same bus chips ripped out from somewhere and stuffed on their PCB. The other large chip is definitely memory. I'm not talking just save game memory, I'm talking the rom of the game. The little one is a 6129 CMOS chip which I would wager is a logic chip (NAND or NOR usually).
Title: It was given by the XKCD moderators to me because they didn't care what I thought (I made some rantings, etc). I care what YOU think, the joke is forums.xkcd doesn't care what I think.

Micron
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Re: Could someone explain these terms?

Postby Micron » Wed Mar 19, 2008 10:14 pm UTC

mosc wrote:This whole thread is mostly dis-information.

That is unfortunate but you seem to be adding more instead of correcting the problem.

You are correct that 'C' does not always indicate a capacitor, I mentioned a couple of times that notation varies between regions and manufacturers. However the International Electrotechnical Commission has sets of standards for PCB reference markings just like they do for resistor color codes and other components. These are not always followed exactly and you'll see more variation in older equipment but the notation is not totally arbitrary.
A capacitor acts like an open circuit to low frequency signals and a closed circuit to high frequency signals. In some cases you can just as easily use a resistor to limit the current through a path while still transmitting a signal. This has nothing to do with "various capacitances between nodes" of a resistor. (If you have no idea what I'm talking about then lookup up the definition of reactance might be a place to start but I don't want to go off on a tangent just to show how much I've forgotten about working in the frequency domain.)

Those little round holes are plated through holes connecting the traces on different layers of the PCB (probably just the front and back in this case). They may be handy for testing but their real purpose is to allow paths to cross without connecting.

We have a pretty good idea what those ICs are. I did link to a pinout for the larger two in my previous post.

I appreciate corrections if I made a mistake but if you're going to call the discussion "dis-information" then at least please try not to make it worse.


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