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 Post subject: Akira TC0190 questions
PostPosted: Wed May 11, 2016 1:09 pm 
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Joined: Fri Apr 29, 2016 8:39 am
Posts: 13
I'd like to apply the fan translation of Akira to my Famicom cart. I already traced out all the pins so I'm not worried about wiring, although there are some things I'm concerned about before I start desoldering:

The fan translation expands the PRG from 128 kilobytes to 256 kilobytes. I'm guessing that this shouldn't be a problem, but I couldn't find a lot of information about this.

Also the game uses two 128 kilobyte CHR mask ROMs, and it looks to be controlled by a 74HC139AP decoder. I'm sort of a layman in terms of how this particular Taito chip handles this, but from what I traced out it appears that the TC0190 sends inputs to the 74HC139AP to decide which CHR ROM chip is currently needed and switches as necessary. This is all guesswork on my part.

What I'd like to know is, could I use a single 256 kilobyte EPROM like a 27C020 and bypass the 74HC139 by soldering leads directly to the TC0190? Or is the program expecting two CHR ROMs and the 74 chip to be in the circuit to function properly?

Finally, assuming I HAVE to use a pair of 128 kilobyte EPROMs for the CHR ROMs, how do I split the CHR file? Every ROM utility I can find spits out a 256 kilobyte CHR bin file, and I didn't want to assume I could just download a generic file splitter program and divide it in two and burn the EPROMs.


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PostPosted: Wed May 11, 2016 1:26 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
DamienC wrote:
The fan translation expands the PRG from 128 kilobytes to 256 kilobytes. I'm guessing that this shouldn't be a problem, but I couldn't find a lot of information about this.
Per http://wiki.nesdev.com/w/index.php/Taito_TC0190_pinout
that should work fine.

DamienC wrote:
What I'd like to know is, could I use a single 256 kilobyte EPROM like a 27C020 and bypass the 74HC139 by soldering leads directly to the TC0190?
Yes.


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PostPosted: Wed May 11, 2016 1:41 pm 
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Awesome, I'll try this out tonight with a 27C020 or 27C040 (depending what I have lying around).

Thanks.


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PostPosted: Fri May 13, 2016 4:54 am 
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Joined: Fri Apr 29, 2016 8:39 am
Posts: 13
OK I thought I had it working but apparently it's being flaky. PRG is fine, the game starts and I can hear music perfectly.

CHR is apparently not right. I swear it worked the way I had this wired because I played the game for a good 20 minutes yesterday, but when I got home and tried again the graphics were corrupted.

The 74HC139AP is removed but I'm using some of the holes as solder points for some pins on the CHR.

Currently my EPROM is wired like this:

Pins 1, 2, 30, 31, 32 lifted
Pin 1 float
Pin 2 to hole 24 (A16)
Pin 22 (CHR /CE?) to 74HC139 hole 3 (PPU A13)
Pin 23 (CHR A10) to 74HC139 hole 1 (PPU /RD)
Pin 30 to 74HC139 hole 2 (CHR A17)
Pin 31 float
Pin 32 to +5V (I tied this to CHR1 pin 28 out of convenience)

I'm almost positive that the issue is PPU A13 and PPU /RD as I'm not entirely positive where to wire them, or if I should be wiring them at all. The wiki (http://wiki.nesdev.com/w/index.php/Cartridge_connector) states that CHR /CE is usually tied to A13 so that's why I had it where it is.

Can anyone point me in the right direction?


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PostPosted: Fri May 13, 2016 10:28 am 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
PPU /RD and A13 should be connected to ROM /OE and /CE respectively.

CHR A0..A9 should come from the card edge. CHR A10..A18 should come from the TC0190 ... at least, up to the size of the image you're trying to burn/flash.


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PostPosted: Sat May 14, 2016 6:13 am 
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Joined: Fri Apr 29, 2016 8:39 am
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lidnariq wrote:
PPU /RD and A13 should be connected to ROM /OE and /CE respectively.


That's it. I had pin 24 (CHR /OE) tied to GND. I moved it to PPU /RD and now it works perfectly.

Thanks.


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