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• PPU (PAL) clock & video

  padnest • 02/21/2022 at 11:01 • 0 comments

  PPU requires a clock signal input at pin 18 and for the UA6538 it must have a frequency of 26.601712 Mhz because it's a PAL chip.

  I don't know what are the clock signal input specifications so I'm trying to use this simple clock generator circuit:

  I'm getting just 2.2 Vpp oscillation but it seems to be ok for the PPU:

  The PPU video output cannot be connectd directly to the TV low impedance AV input: we need a video buffer circuit like this one:

  See you next time!

  Ciao!

• ...alive, it's alive..., it's aliveeeeeeeee...​

  padnest • 02/20/2022 at 08:51 • 0 comments

  I'm feeling like the young doctor Frankenstein in moments like this.

  I have connected all signals trying to keep the wires as short as possible:

  I want to keep memory signals well separate from video out and clock generator, this is the BB main chips layout:

  After giving the power supply we got a nice PAL video signal at pin 21.

  This is the first PAL line:

  This is the PAL line #44:

  This is the last PAL line #312:

  We can move on now, see you next update!

  Ciao!

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