iNes mapper 76 with 256 KiB?

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mightydidz
Posts: 99
Joined: Wed Jan 24, 2018 12:04 pm

iNes mapper 76 with 256 KiB?

Post by mightydidz »

I was looking online to see if there is a way to upgrade PRG size on an original Namcot board instead of hacking a mmc3?
http://forums.nesdev.com/viewtopic.php?f=28&t=13990

Idealy I would like to add extra hardware but havent found anything for Namcot108
https://wiki.nesdev.com/w/index.php/Use ... r_thoughts

I'd like to try a Megami Tensei: DDS English translation.
Anyone successfully made this repro?

Thanks
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krzysiobal
Posts: 1037
Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland
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Re: iNes mapper 76 with 256 KiB?

Post by krzysiobal »

What parts are available?
Decoder: 74139 / 74138
Latch: 74161 / 74670 / 74273 / 74174 / 7474

I think you would need around 4-5 chips, this is my opinion not worh doing that way.
Single PAL16L8 can do the trick.

I made two PAL16L8 fusemaps (don't forget to connect externally LOOPIN and LOOPOUT):

*first one (mmc3_predecessor_prg_a17) can be used to add PRG-A17 to your mapper:
mmc3_predecessor_prg_a17.zip
(2.09 KiB) Downloaded 109 times

Code: Select all

                             ._____    _____.
                             |     \__/     |
              CPU_nROMSEL -> |  1        20 | -- VCC
                  CPU_RnW -> |  2        19 | -> LOOPOUT ------+
                  CPU_A14 -> |  3        18 | NC BREG7         |
                  CPU_A13 -> |  4        17 | NC BREG6         |
                   CPU_A0 -> |  5        16 | NC IO4           |
                   CPU_D4 -> |  6        15 | NC BSEL2         |
                   CPU_D2 -> |  7        14 | NC BSEL1         |
                   CPU_D1 -> |  8        13 | NC BSEL0         |
                   CPU_D0 -> |  9        12 | -> PRG_A17       |
                      GND -- | 10        11 | <- LOOPIN -------+
                             |______________|
*second one (mmc3_prg_a19) can be used to add PRG-A19 to regular MMC3 (it even respects the PRG swap bit!):
mmc3_prg_a19.zip
(2.21 KiB) Downloaded 91 times

Code: Select all

                             ._____    _____.
                             |     \__/     |
              CPU_nROMSEL -> |  1        20 | -- VCC
                  CPU_RnW -> |  2        19 | -> LOOPOUT ------+
                  CPU_A14 -> |  3        18 | NC BREG7         |
                  CPU_A13 -> |  4        17 | NC BREG6         |
                   CPU_A0 -> |  5        16 | NC BSEL6         |
                   CPU_D6 -> |  6        15 | NC BSEL2         |
                   CPU_D2 -> |  7        14 | NC BSEL1         |
                   CPU_D1 -> |  8        13 | NC BSEL0         |
                   CPU_D0 -> |  9        12 | -> PRG_A19       |
                      GND -- | 10        11 | <- LOOPIN -------+
                             |______________|
	
GAL16V8 is for 0.22$/piece on aliexpress :D
mightydidz
Posts: 99
Joined: Wed Jan 24, 2018 12:04 pm

Re: iNes mapper 76 with 256 KiB?

Post by mightydidz »

I only have a superpro 610p for programming.
What would i need to program those logic array ic?
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