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PostPosted: Fri Aug 25, 2017 8:17 am 
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I wonder if this COB famiclone that krzysiobal found contains a UM6561.

There's a bunch of pins over there in the corner (18,19, maybe another one or two) that might not be supply pins and might change the behavior if tied high or low.


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PostPosted: Fri Aug 25, 2017 1:22 pm 
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Seems to be the official datasheet of UM6561 :
http://bbs.a9vg.com/thread-5103544-1-1.html


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PostPosted: Sat Aug 26, 2017 3:03 am 
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I have spare UM6561 for testing
Image Image

and there is direct connection only between those GND pins: 73, 60, 16.

Other pins marked as GND or NC in this schematics (32, 18, 19) might act as input pins. There is high probability of it, as multimeter on diode test shows some value for EACH of those pins with respect to GND, so they are internally connected.


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PostPosted: Sun Aug 27, 2017 8:04 am 
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The datasheet that Farid found for the UM6561 says that pin 19 is P1 D2 (i.e. famicom microphone).

I notice that he switched pin 32 from ground (in the initial pinout) to 5V (in his very first breadboarded picture, pin 32 is labelled "GND 5V")


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PostPosted: Sun Aug 27, 2017 12:58 pm 
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Quote:
The datasheet that Farid found for the UM6561 says that pin 19 is P1 D2 (i.e. famicom microphone).

If it is Famicom microphone should I connect it GND (as suggested in Russian schematic) or leave it floating?

Quote:
I notice that he switched pin 32 from ground (in the initial pinout) to 5V (in his very first breadboarded picture, pin 32 is labelled "GND 5V")

It is definitely mislabeled in the Russian schematic since it is connected to other VCC pins internally.

And here is something interesting :
Quote:
跟据文章描述,改N制只要把晶振换成21.47727MHz就行了。

Google translate :
Quote:
According to the article described, change the N system as long as the crystal into 21.47727MHz on the line.


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PostPosted: Sun Aug 27, 2017 1:30 pm 
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I confirm, pin 32 is connected to VCC. So out of those mysterious pins, only 18 is unknown, so it is probably pal/ntsc select.


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PostPosted: Sun Aug 27, 2017 2:26 pm 
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FARID wrote:
If [pin 19] is [P1 D2] Famicom microphone should I connect it GND (as suggested in Russian schematic) or leave it floating?
Either's fine.


Google OCRs the first two paragraphs of the data sheet as
Quote:
在众多的中英电脑学习机中,用6561芯片开发出来的学习
机,可谓品牌众多。如“科王926”,“声霸”,“小霸王”,“小博士”
等,目前该芯片构成的学习机维修资料很少,本人从事UM6561
芯片的开发,维修多年,近一年又维修了一些中英文电脑学习
机,现将维修资料和检修实例整理出来与同行共享.

目前国内销售的UM6561集成块是UM6561 PAL / NTSC,
该芯片用26.601712MHz的晶振时,视频输出PAL彩色信号,
当使用21.47727MHz的晶振时,视频输出NTSC彩色电视信
号,这类中英文学习机在型号升级时(如486型到926型)从硬
件上看没有实质性的改变. 大多都是增加新的软件功能,也就是
学习卡中内容不同.
It does sound like it autodetects crystal frequency and switches between NTSC and Dendy behavior accordingly.


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PostPosted: Thu Nov 02, 2017 7:21 pm 
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Location: Poland
I just got one famiclone with glob-top UM6561 (soldered on add-on board), but there is also place for regular 80 pin SMD UM6561. What is weird, its pinout it shifted from original UM6561 (this pin1 = UM6561 pin2, this pin 2 = UM6561 pin3).

Image

This board uses 26.601712 MHz crystal and has place for two jumpers - one marked as P/N and the other 50/60 (both were unsoldered, but soldering shorted each of them to GND).

Shorting P/N causes PAL screen to momentally switch to black/white, shorting 50/60 causes TV to lose sync (it is responsible for crystal selection).

So I did this clever switch and now I can in runtime switch between PAL and NTSC - curiously switching crystal during runtime does not cause CPU to break.
Image
I was worried if connecting crystal with only one leg and putting second leg on long wire and switch will have problems, but nothing that happened!


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