Re: VIC-II initialization.

Am Samstag, 29. Mai 2021, 21:56:13 CEST schrieb Michiel Boland:
> On 5/29/21 7:45 PM, tokafondo wrote:
> > I've been studying the VIC-II datasheet and how the C64 initializes it
> > when
> > booting.
> >
> > The only thing I've seen while booting is
> >
> > LDX $#FF
> > [...]
> > STX $D016
>
> This may be a leftover from the commodore max, where apparently there was a
> reset bit in the VIC-II that could be set to 1 to stop the chip. But this
> bit does nothing in the commodore 64.
>
> I believe all registers in the VIC chip are initially zero, except for
> registers that are implemented using S/R-latches, which may contain random
> data. I haven't looked at this for a while but I think the sprite collision
> registers and the lower bits of the interrupt register use S/R-latches or
> something similar.
>
> I think the light pen registers also sometimes contain random data after
> powerup, not sure exactly how that works.
>
> Also famously the sprite counters are not initialized at powerup so these
> contain random data. (Although these are not available as registers.)

That sounds pretty accurate :) The usual testprogram is here:
https://sourceforge.net/p/vice-emu/code/HEAD/tree/testprogs/C64/autostart/
defaults/


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