On Wednesday 21 June 2017, 14:08:43 Segher Boessenkool <segher@kernel.crashing.org> wrote: > On Wed, Jun 21, 2017 at 06:46:08PM +0100, smf wrote: > > On 21/06/2017 18:29, silverdr@wfmh.org.pl wrote: > > >... that I never used LP IRQs but thought that it would trigger only > > >when the button line is grounded within a specific timing window so > > >some kind of synchronisation with raster position would be required > > >for the IRQ to happen. But that's a different subject anyway. > > > > A light pen is a simple sensor that triggers when a brighter than normal > > light is detected. The VIC just latches the x & y position & fires an > > IRQ when it is triggered, because it assumes that if the light pen can > > see the gun then it must be over the current pixel. > > > > Adding something to VIC to ignore pulses outside the visible portion of > > the display would be a waste of space. > > IIRC the LP stuff can be triggered only once per frame, this makes it > a bit inconvenient to use for non-lightpen uses like we are discussing > here. It would be nice if we could just read out the current X coor > directly, but nope. wasnt that also different between VIC revisions.... older one will trigger only once per frame, newer can do it any time again? like with sprite collision? -- http://www.hitmen-console.org http://magicdisk.untergrund.net http://www.pokefinder.org http://ar.pokefinder.org Man kann auch saufen statt rumweinen. Hilft gleichzeitig der Wirtschaft und dem Staat! <Yago/K2> Message was sent through the cbm-hackers mailing listReceived on 2017-06-21 20:02:23
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