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 Post subject: TKROM schematic?
PostPosted: Fri Jan 20, 2017 2:18 pm 
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Joined: Wed Apr 07, 2010 1:14 am
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Location: Iran
We had a discussion about SKROM before so those info can be applied to TKROM.
But the function of some analog parts were not found.
Can anyone please explain the function of the remaining parts?

B1 (CR2032) : supply power for WRAM when Famicom is turend off in order to keep save data.

D1 (1N4147) : ?
D2 (1N4148) : prevent CR2032 from powering the whole cartridge.
R2 (1K) : prevent WRAM from using CR2032 when the game runs.
CB (22uF) : when the power is turned off, the voltage will slowly decrease from 5V to 3V instead of doing a sharp edge.

R1 (10K) : disable WRAM when the power is off.

R3 (27K) : pull down resistor for M2 in order to prevent unwanted writes to WRAM

C1 (22uF) : ?

C2 (100nF) : bypass capacitor for CHR.

CC (220pF) : ?


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 Post subject: Re: TKROM schematic?
PostPosted: Fri Jan 20, 2017 3:03 pm 
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Location: Seattle
D1: prevent +5V from accidentally charging the CR2032
C1: voltage rail stabilization for entire PCB (bypass caps are often both one small one, with a very low ESR, to handle transients; and a large one, to handle variation in load over a longer time scale)
CC: Delays PPU A12 for some reason. Has to have something with how MMC3 IRQs work. We're not clear on the specifics.


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 Post subject: Re: TKROM schematic?
PostPosted: Thu Feb 02, 2017 7:14 pm 
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Joined: Wed Jul 13, 2011 6:51 am
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Location: Brasilia, Brazil
I believe the reason they need to delay PA12 (Ppu Address?) is to make up for internal propagation delay at the MMC3. If the capacitor is missing IRQ will trigger at a incorrect/erratic time causing the screen split to fail (happen at random lines on the display).


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