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PostPosted: Wed Mar 13, 2019 5:31 pm 
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Joined: Tue Jun 24, 2008 8:38 pm
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Location: Fukuoka, Japan
It's around 20$ in japan at cybergadget:

Attachment:
4544859022630.jpg
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I may buy one someday but for some reason they sell it at an exorbitant price on amazon.jp so I don't know if it's means it's discontinued or not.


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PostPosted: Wed Mar 13, 2019 10:02 pm 
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Joined: Tue Mar 22, 2016 8:27 pm
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Location: Minnesota, USA
Banshaku wrote:
It's around 20$ in japan at cybergadget:

Attachment:
4544859022630.jpg


I may buy one someday but for some reason they sell it at an exorbitant price on amazon.jp so I don't know if it's means it's discontinued or not.

I like it, it looks very nice. It is nice that it is keyed on both sides so nothing can go backwards. I have put a cart in backwards once by accident. Amazingly nothing broke.


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PostPosted: Thu Jul 18, 2019 12:37 am 
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Joined: Fri Mar 23, 2018 8:58 pm
Posts: 37
I have a question about the circuit.

Why connect PRG A14 and PRG A13 to 74'139 and AY-3-8910, rather than CPU A14 and CPU A13? We are trying to decode CPU memory region $C000~$FFFF, not PRG, aren't we?
Connecting PRG /CE rather than CPU /ROMSEL to 74'139 is also confusing me.

I found that what we are trying to do is quite similar with PRG RAM circuit. The sole difference is the address region. Am I correct?


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PostPosted: Thu Jul 18, 2019 1:54 am 
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Joined: Sun Jun 12, 2011 12:06 pm
Posts: 540
Location: Poland
It is CPU, not PRG, as you correctly think.


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PostPosted: Thu Jul 18, 2019 2:07 am 
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krzysiobal wrote:
It is CPU, not PRG, as you correctly think.

So this is the "not so confusing" circuit, right?

Code:
          74'139
         -----v-----
     GND-|/1E   VCC|-+5V
139./2Y1-|1A    /2E|-CPU /ROMSEL
139./2Y1-|1B     2A|-CPU A14
        -|/1Y0   2B|-CPU R/W
        -|/1Y1 /2Y0|-
        -|/1Y2 /2Y1|-139.1A
 AY.BDIR-|/1Y3 /2Y2|-
     GND-|GND  /2Y3|-
         -----------

AY-3-8910
----v----
    .   |
    .   |
    .   |
     BC1|-GND
     BC2|-CPU A13
    BDIR|-139./1Y3
    .   |
    .   |
    .   |
---------


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PostPosted: Thu Jul 18, 2019 3:15 am 
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Joined: Sun Jun 12, 2011 12:06 pm
Posts: 540
Location: Poland
Yep, and 8910.A8=VCC, 8910./A9=GND, 8910.CLK=M2 divided by 2


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PostPosted: Thu Jul 18, 2019 3:28 am 
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Joined: Fri Mar 23, 2018 8:58 pm
Posts: 37
krzysiobal wrote:
Yep, and 8910.A8=VCC, 8910./A9=GND, 8910.CLK=M2 divided by 2

Thank you krzysiobal! I'll try making my reproduction.


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