> > However, one problemo...
> > When I set the adjust while a VDP-command is executing, there appear
some
> > 'noise'-pixels on the screen. I can avoid that to happen by exact timing
of
> > my COPY's (execute them right after the V_BLANK-interrupt), but I would
like
> > that different (because it will also decrease the time left for other
> > copies, i.e. the displaying of the character).
> >
> > Does anyone know a solution for that???
Mark Zellenrath wrote:
> These random flickering pixels are a pretty well-known phenomenon.
> They appear whenever you change r#18 (Set Adjust register), while the
> VDP is executing a COPY-command. Knowing this, the solution is obvious.
> Just change change r#18 *before* you give the COPY commands or *after*
> the COPY-commands have been executed.
Frits Hilderink wrote:
> The solution was changing the sequence in which the vdp registers where
written:
> are you writing register 18 before or after the command that you are
executing.
Yes. Well, I change r#18 on the interrupt and I execute my COPY right after
the V_BLANK interrupt. So at the moment there is no problem. But this
screensplit is 52 lines high, so I can't execute COPY-commands at the 160th
and the 212th line, which decreases a lot of my time left for other COPYs. I
might be able to time it very carefully so I can insert some small COPYs
between those lines, but I hoped there was another solution for my problem
so that I wouldn't have to time that careful.
But, unfortunately, I guess I'm doomed now...
However, I made up a slight solution in the meantime, I don't know if it
works yet, but if it does it will make an end to the errors: Before I change
register 18 I will check if the Command Execute status-bit is set. If so, I
will send a STOP command to the VDP, and after that I will change register
18. After I've set VDP 18 I will resend the command the VDP was executing
(which I stored). If my information (that is the tables in Stefan Boer's VDP
cursus) is correct, this should work.
But I will have to test that to know if it really works... Does anyone know
if sending the STOP-command can result in an erroneous (???correct
English???) byte displayed?
~Grauw
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