so its jsut the sam 192 line interrupt but due to the speed of the processor you could only use 128 interrupts maximum didnt it say in the technical manual with a 4¾mhz sam processor unless in mode1 which is slower no or rom or external ram which might be a bit quicker mebbe? so the line drawing routine doesnt draw the odd or even scan line pixels first then the remaining pixels as the screen is displayed in two pal frames no?
2009/10/8 Colin Piggot <qua...@clara.net>: > 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 > ===== > Quazar : Hardware, Software, Spares and Repairs for the SAM Coupe > 1995-2009 - Celebrating 15 Years of developing for the SAM Coupe > Website: http://www.samcoupe.com/ >
