Thanks to Thierry Bouterin posting PCB photos on the PCW Facebook group, I think I now understand the VIDI-PCW digitiser well enough to write it up in my PCW Hardware document, if not to emulate it. It looks as if it’s based around a 6845 CRTC and 24k of static RAM. So the process from the Stop Press point of view is to start the CRTC, wait until it has captured a frame, stop the CRTC and then read the frame in from the digitiser’s internal buffer. It probably wouldn’t be hard to emulate, though I’m not sure I’d see the point of so doing.
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I saw the post on Facebook…
What you’re describing there is the scanning feature of the VIDI-PCW. However, this model — the one shown in the photos you’re talking about — isn’t just an image scanner. It can also send the PCW’s own video signal to the VIDI-PCW’s video output, allowing the PCW display to be mirrored on an external video monitor.
Many years ago, I knew someone who used one with a video projector to give presentations, back before PowerPoint existed. Unfortunately, that person is no longer with us, and I have no idea what became of their equipment, as I only knew them professionally.
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I’ve seen that done (at the Crawley PCW club). They later had a device built by Christopher North that replicated the output half of the Rombo and allowed a PCW to replicate its display on several mono TVs. There’s a circuit diagram for it on my Joyce page. I didn’t discuss the output functionality of the Rombo in the PCW Hardware document because it’s entirely separate from the image capture function, and is entirely transparent to software running on the PCW.
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Also, while I’m here, thank you for all the work you’ve done on Joyce and around the PCW over the years. It’s incredibly useful to all of us.