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I'm nearly finished with the recreation of a PCB that'll be used in creating a modchip for my PlayStation 1 that is gathering dust. I'm basing it off a modchip I bought last year but accidentally threw out while cleaning and contacting the seller to purchase a new one now is difficult.

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Right now I have the capacitor connecting to the pads that are connected to where pin1(VDD) and pin8(VSS) of a PIC12F508-I/SN will be mounted. I have absolutely no idea if this is correct and if it is not where should I be connecting it to?

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  • \$\begingroup\$ You say you're copying an existing design. Do you have access to the code of the original design? The PIC12F508 is a microcontroller which requires a program to run, and without that code it won't do anything useful. \$\endgroup\$ – Hearth Nov 5 '18 at 13:18
  • \$\begingroup\$ The Hex files for creating PS1 mod chips are widely available for anyone to use/modify and is what the original chip that was accidental thrown out used. In my case I'm using the Mayumi V4 Hex for my PAL SCPH-5552 PS1. The only thing I'm recreating is the PCB. Afaik the PIC12F508 is just the popular choice for modders, usually in the PDIP package and not the SOIC package though. \$\endgroup\$ – Katcher Nov 5 '18 at 13:46
  • \$\begingroup\$ Okay. I just wanted to make sure you weren't going to all this trouble just to later learn that it won't work. \$\endgroup\$ – Hearth Nov 5 '18 at 13:48
  • \$\begingroup\$ Isn't that half the fun? To be fair though, I haven't the slightest clue how to program the SOIC package of the PIC12F508 I'm going to use. As for the PDIP though I know of a tutorial, on the same site I can grab the Hex files from, that shows me how to build a JDM programmer. \$\endgroup\$ – Katcher Nov 5 '18 at 13:52
  • \$\begingroup\$ Well, if you encounter problems programming it, you're certainly welcome to ask another question about that here. \$\endgroup\$ – Hearth Nov 5 '18 at 13:53
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You have the decoupling capacitor connected to the correct pins on that IC, that's for sure. However, it is a good rule of thumb to have a decoupling capacitor as close as possible to the pins on the IC it is decoupling (for one source, look here http://www.capacitorguide.com/coupling-and-decoupling/, though nearly every article you read will talk about how they need to be close to the IC).

However, if your board needs to be single layer and/or it needs to be that size, I wouldn't worry too much.

What capacitance have you chosen?

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    \$\begingroup\$ I was advised on using a 100nF capacitor on another site when initially trying to figure out it was an MLCC on the original board. I'm glad I put the capacitor to the right pins. My reasoning was, "capacitor stores energy, Vdd and VSS seem to be for Voltage, it must go there" \$\endgroup\$ – Katcher Nov 5 '18 at 10:35

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