The VIC-II
knows at any given point in time which pixel coordinate the
raster beam is currently at. Within the light pen is a sensor which can
pick up the presence of the beam.
Does that mean the screen must be non-black for a light pen to work?
As far as the C64 goes, "black" isn't quite black. There's some
residual
light generated, and the light pen will pick it up.
--
---------------------------------- personal:
http://www.armory.com/~spectre/ --
Cameron Kaiser, Floodgap Systems Ltd * So. Calif., USA * ckaiser at
floodgap.com
-- Research is what I'm doing when I don't know what I'm doing. -- W. von
Braun