Re: NTSC VIC-II timing

Date: Wed, 21 Jun 2017 19:40:25 +0200
Message-ID: <4894570.L1QK3oAPTA@rakete>
On Wednesday 21 June 2017, 19:29:06 wrote:
> > On 2017-06-21, at 19:17, Gerrit Heitsch <> wrote:
> >>> Excellent fun!  It sees if the light pen interrupt can be triggered
> >>> between raster lines x'136 and 2; if so, it's a 6569R1, if not, not.
> >> 
> >> That's very interesting too! How does one trigger LP IRQ from within
> >> software alone? Is it a kind of raster position / CIA port combination?> 
> > Well, the LP Input is connected to the joystick ports and shares a Pin
> > with PB4 of the CIA on U1.
> Hardware side sure. What I meant was...
> > So you can trigger LP IRQs via software.
> ... 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.

check this code:

Das Schwierigste am Diskutieren ist nicht, den eigenen Standpunkt zu 
verteidigen, sondern ihn zu kennen. 
<André Maurois>

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Received on 2017-06-21 18:03:51

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