New MIST core: PC Engine!

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Sorgelig
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Re: New MIST core: PC Engine!

Postby Sorgelig » Wed Mar 01, 2017 1:03 pm

I didn't see the code of PC engine, but such strange problems can happen if core uses async design. FPGA doesn't work well with async design (when some random signals used as a clocks).
VSync/HSync are logic signals, so resistors won't help you here.

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DrOG
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Re: New MIST core: PC Engine!

Postby DrOG » Wed Mar 01, 2017 2:10 pm

I understand.

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@ Sorgelig:
What about the other phenomenon mentioned in the undermentioned topic:

viewtopic.php?f=101&t=28506&p=312422#p312422

You, as creator of the YPbPr adaptor, perhaps measured the sync signal using oscilloscope. Shall we use a resistor to protect our devices, or it is unnecessary/useless? Or does it depend on the actual core?

Something similar would be nice and composing (the Enterpise 128 has also TTL level sync signals):

https://enterpriseforever.com/hardware/ ... art-cable/

Sorgelig
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Re: New MIST core: PC Engine!

Postby Sorgelig » Wed Mar 01, 2017 10:41 pm

You can check MiST schematic by yourself. HSync/VSync are LVTTL signals. They only can be in '1' state which is ~2.5V and '0' state which is 0V. It's true and equal for all cores. They go through 100 Ohm resistors. TV usually has 75 OHm pull down resistors on these signals make HSync/VSync 1/4 of original amplitude.
I don't see any problem from sync level for any TV/Monitor even if full 2.5V amplitude will be passed (if TV/Monitor doesn't have pull down resistors). I suggest to stop playing with resistors if you don't want to brake the board in your experiments.

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DrOG
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Re: New MIST core: PC Engine!

Postby DrOG » Thu Mar 02, 2017 4:05 am

OK, thanks! :oops:


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