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PostPosted: Wed Apr 26, 2017 12:16 am 
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Joined: Sun May 22, 2016 9:29 am
Posts: 9
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


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PostPosted: Wed Apr 26, 2017 12:34 pm 
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Joined: Fri Jul 04, 2014 2:34 pm
Posts: 292
Location: Germany
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.


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PostPosted: Wed Apr 26, 2017 11:20 pm 
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Joined: Sun May 22, 2016 9:29 am
Posts: 9
You are right,thanks - so i could use 2 27801 and rewire!


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PostPosted: Thu Apr 27, 2017 1:25 am 
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Joined: Fri Jul 04, 2014 2:34 pm
Posts: 292
Location: Germany
Yea, that would be the better method for those boards. :P


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