Re: (i) counting frames; (ii) emulators in general

[Colin Piggot]

Thomas wrote:
(1)  I'm vaguely aware that there's a "current scanline" hardware
counter somewhere - does that count actual PAL lines or only lines
with pixels on them?

HPEN port (&01f8) will give the current scanline - for scanlines in the 
display area only (0-191 iirc)

And how long does the end-of-display interrupt signal last? My memory
is saying 24 cycles, but I'm not sure why. I guess since we're on a
system with no explicit interrupt acknowledgments, it's going to be
something tiny?

If I also remember correctly from all the tinkering I've done, the interrupt 
pulse lasts for 128 clock cycles.

Colin
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Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe
1995-2009 - Celebrating 15 Years of developing for the SAM Coupe
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