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PostPosted: Sat Mar 02, 2013 1:24 pm 
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I recently found this flashcart:
http://zdoom.ic.cz/gameboy.html
When you look at the schematic there is on the lower right some signs I can't decipher, so I need help.
In the description it is said that there is 7400 logic connected to the cart, but I am not sure if the logic is the thing drawn in the lower right or if it is something else.
I also would like to know if the firmware written to the bootup EEPROM is able to copy MBC5 games to the SRAM because the project was originally designed for MBC1, but I wanted to use MBC5.
Thanks in advance.


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PostPosted: Thu May 30, 2013 1:23 am 
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I assume you mean the NAND gates in which case, yes, that is the 7400 logic he mentions


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PostPosted: Wed Jun 19, 2013 3:46 pm 
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This would be neat to see implemented to the Super Game Boy.


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PostPosted: Thu Jun 20, 2013 2:13 pm 
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marvelus10 wrote:
This would be neat to see implemented to the Super Game Boy.

That would be more complicated than on a DMG since the same lines are also used for communicating with the SNES CPU. Sending commands to the SD card might also trigger SGB commands. There are various things you could do to prevent that, but yeah, it gets more complicated.


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PostPosted: Thu Jun 20, 2013 2:43 pm 
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There's got to be a less goofy solution than using 13 NAND2 gates...

I think you could replace them with two 74'139s (instead of 3¼ 74'00s)


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PostPosted: Sun Jun 23, 2013 11:30 am 
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that would be awesome if you could replace the nand gates with '139 because it takes a long time to figure out the wiring and it would not take as much space as the 4 7400 take.
i am finished with wiring everything up, but it would not read my sd card :( it detects the sd card and tries to load it but it doesn't read it's content


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PostPosted: Sun Jun 23, 2013 1:31 pm 
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Using the gameboy keypad as I/O seems a little goofy; permanently wired formerly-interchangable parts seem wasteful to me. But let's see…
The eight NAND gates in the lower right, or what he calls "MBC/RAM !WR enable selection" in the article:
1_139./1G ← EA0
1_139.1A ← EA1
1_139.1B ← P14
1_139./1Y3 → 1_139.2B

1_139./2G ← ground
1_139.2A ← 1_139./1Y3 ( repeating myself for clarity )
1_139.2B ← /WR
1_139./2Y0 → /RWR
1_139./2Y1 → /MWR

The two NAND gates in the lower left, or what he calls "MMC/SD !CE" in the lookup table in the article:
2_139./1G ← ground
2_139.1A ← EA0
2_139.1B ← EA1
2_139./1Y2 → /SD-CS

The remaining three NAND gates, unnamed:
2_139./2G ← ground
2_139.2A ← EA1
2_139.2B ← A15
2_139./2Y0 → /ECS
2_139./2Y1 → /RCS

Anyway, any of the four selectors can be swapped around as necessary.


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