Nintendo World Championship 1990 - reverse engineering

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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krzysiobal
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Location: Poland

Nintendo World Championship 1990 - reverse engineering

Post by krzysiobal » Sun Sep 08, 2019 1:26 pm

One guy asked me to analyze this cartridge. Fortunatelly there were photos of PCB on the web so I give a chance.
There is one think I cannot agree with the Mapper 105 description:
On powerup and reset, the first 32k of PRG (from the first PRG chip) is selected at $8000 *no matter what*.
PRG cannot be swapped until the mapper has been "initialized" by setting the 'I' bit to 0, then to '1'. This
toggling will "unlock" PRG swapping on the mapper.
Because the MMC1-PRG-A14 is directly connected to both EPROMS, if MMC1 is switched into 16K+16K mode and MMC1 PRG's bank is modified, $8000 might stop pointing to first 32k even without rising edge on `I` bit.

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pakosup
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Re: Nintendo World Championship 1990 - reverse engineering

Post by pakosup » Mon Sep 09, 2019 3:00 am

Probably pull-up resistors are missing for 74hc30

krzysiobal
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Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Re: Nintendo World Championship 1990 - reverse engineering

Post by krzysiobal » Mon Sep 09, 2019 4:04 am

Yes sorry, I did not notice there is VCC pull-up 4xresistor ladder above the switch (if that were LS, not HC - pull-ups wouldnt be needed)

nocash
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Re: Nintendo World Championship 1990 - reverse engineering

Post by nocash » Mon Sep 09, 2019 6:12 am

Those 4-in-1 resistor components are called "resistor networks".
A resistor ladder is something else (a circuit related to digital/analog conversion).
Either way, it's hard to see on the photo, I wasn't sure what you were talking about, until noticing the "shadow" behind the DIP switches.

FrankWDoom
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Re: Nintendo World Championship 1990 - reverse engineering

Post by FrankWDoom » Mon Sep 09, 2019 1:46 pm

Kevtris' writeup mentions the cic reset line is connected to something else on the board, what's going on with that?

lidnariq
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Re: Nintendo World Championship 1990 - reverse engineering

Post by lidnariq » Mon Sep 09, 2019 1:58 pm

CIC reset is used to force the game into the menu on reset, instead of using a diode, resistor, and capacitor to detect A0 or M2 going high impedance.

krzysiobal
Posts: 649
Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Re: Nintendo World Championship 1990 - reverse engineering

Post by krzysiobal » Mon Sep 09, 2019 2:31 pm

I fixed the schematic - pin 7 of CIC is the one used to detect reset and which comes from edge connector, not pin 9.
Image

I like how Nintendo routed all pins of all chips either out of the board or to to a place where a hole was drilled,, even those non connected to anything to short them while gold plating. That helps in guessing!

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