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 Post subject: Schematic for UM6561?
PostPosted: Thu Jan 05, 2017 1:09 pm 
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Well first of all HAPPY NEW YEAR :beer:

I want to make a mini Famicom clone by using UM6561 + two EPROM so that I can run simple NROM games on it.
I am testing the circuit on a breadboard :

Image


I found a Dendy schematic which is based on UM6561 but it seems it has some errors in it :
(capacitor signs are Russian : MK=uF / H=nF / n=pF)

Image


Fortunately I have a Famicom clone named FUMA-001 which uses the same chip :

Image

Image


By comparing them I found out that their circuit is very different so I have to compare them with another famous Famicom schematic :

Image


Also I want to omit RF and its related parts so that the whole thing become more compact.


Last edited by FARID on Thu Jan 05, 2017 2:02 pm, edited 1 time in total.

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PostPosted: Thu Jan 05, 2017 1:25 pm 
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Dendy :
Image

Fuma :
Image

Famicom :
Image

80sFREAK :
Image

Output :
Image

console5.com :
Image

Output :
Image


Last edited by FARID on Sun Jan 08, 2017 10:17 am, edited 2 times in total.

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PostPosted: Thu Jan 05, 2017 1:33 pm 
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Audio :

Dendy :
Image

Fuma :
Image


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PostPosted: Thu Jan 05, 2017 1:38 pm 
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7805 official datasheet suggest to use 0.1uF and 0.33uF but in Dendy and Famicom they used 47uF and 470uF :

Dendy :
Image

Fuma (it seems caps are swapped wrongly?) :
Image

7805 Datasheet :
Image


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PostPosted: Thu Jan 05, 2017 1:46 pm 
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Dendy (suggests to use 470nF (=0.47uF) Electrolytic capacitor) :
Image

Fuma (uses 100nF Ceramic capacitor) :
Image

Famicom (suggests to use 0.47uF Electrolytic capacitor) :
Image

so which one should I use?


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PostPosted: Thu Jan 05, 2017 1:53 pm 
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Famicom :
Image

Dendy (both caps for crystal are 30pF) :
Image

Fuma (Caps are different 39pF and 12pF) :
Image


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PostPosted: Thu Jan 05, 2017 1:56 pm 
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FARID wrote:
7805 official datasheet suggest to use 0.1uF and 0.33uF but in Dendy and Famicom they used 47uF and 470uF :
I've seen different specified capacitances there, depending on the nature of the input voltage and the technology of the capacitor.

Larger capacitances are needed when you have full- (or half-) wave rectified AC and the capacitor has to hold enough power to keep everything running for up to 10ms between mains.

On the low side, a better ESR will improve AV quality.

FARID wrote:
Dendy (suggests to use 470nF (=0.47uF) Electrolytic capacitor) :
Fuma (uses 100nF Ceramic capacitor) :
Famicom (suggests to use 0.47uF Electrolytic capacitor) :
so which one should I use?
On the 2A03 (I can't speak for the Dendy parts), the reset pin has a depletion NMOS pullup inside. When I measured mine, that pin emits somewhere between 20 and 50 µA continuously, only vaguely a function of the output and supply voltages.

The choice of capacitor only determines how long the CPU is held in reset after power up or after the user presses the reset button. A larger value will take longer.

The specific value doesn't seem to matter much, as long as the CPU comes out of reset consistently.


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PostPosted: Fri Jan 06, 2017 12:13 pm 
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It works fine :

https://youtu.be/P-ByTSWdE84

Schematic Rev 2 :
- Better circuit for Video output
- Fixed some mistakes


Attachments:
um6561_rev2.PNG
um6561_rev2.PNG [ 37.74 KiB | Viewed 52 times ]
UM6561.PNG
UM6561.PNG [ 37.4 KiB | Viewed 122 times ]
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