Re: NTSC VIC-II timing

Date: Wed, 21 Jun 2017 20:15:25 +0200
Message-ID: <7431056.0c6isWDGfo@rakete>
On Wednesday 21 June 2017, 20:12:41 wrote:
> > On 2017-06-21, at 19:44, Gerrit Heitsch <> 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.> 
> > No, the LP IRQ just latches the current X and Y position of the electron
> > beam when you get the high to low transition on the LP line. And you also
> > get an IRQ to notify you of that event.
> > 
> > On 2017-06-21, at 19:46, smf <> wrote:
> > 
> > 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.
> But that means that I can basically trigger valid LP IRQs using joystick and
> pushing its fire button..

...and by pressing SPACE, correct :)


The thing is, I HAVE learned Excel, C and MATLAB and nothing in there compares 
with the simplicity, easy of use and time saved of using good old Basic V2. 

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Received on 2017-06-21 19:02:32

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