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29F016 on 2A3B (2 Maskrom) Donor
http://forums.nesdev.com/viewtopic.php?f=28&t=15856
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Author:  twitch [ Wed Apr 26, 2017 12:16 am ]
Post subject:  29F016 on 2A3B (2 Maskrom) Donor

Hi Folks!

i have several 2A3B PCB laying around and im asking myself if i can just put a 16Mbit TSOP in Maskrom1(U1) and leave Maskrom2(U2) empty?

For example: Parallel World? (LoRom 64k)

Will this work and is there any wiring needed on the 74LS?

Rgds Dario

Author:  Ice Man [ Wed Apr 26, 2017 12:34 pm ]
Post subject:  Re: 29F016 on 2A3B (2 Maskrom) Donor

You have to rewire the 74LS139 since 2A3B only has 32 pin MaskROMs.
You'd need to make up for A20/A21 decoding when using a TSOP Adapter with 36 pins.

Author:  twitch [ Wed Apr 26, 2017 11:20 pm ]
Post subject:  Re: 29F016 on 2A3B (2 Maskrom) Donor

You are right,thanks - so i could use 2 27801 and rewire!

Author:  Ice Man [ Thu Apr 27, 2017 1:25 am ]
Post subject:  Re: 29F016 on 2A3B (2 Maskrom) Donor

Yea, that would be the better method for those boards. :P

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