Re: Mix LGR and Text?

[bieling@terra.es (Jorge Chamorro Bieling)]

Bryan,

I also loved playing around with this things. Just some thoughts:

In order to switch in/out a *known*, fixed band of every single picture
frame you'd need to be able to lock to the vertical sync. If not, you
can only be sure that you're switching in/out a certain portion of the
frame at the right frequency. I believe IIe's have had vsync
memory-mapped, but i can not figure out how did you manage to know when
it's vsync-time on an a2, a2+ ? I'm telling you because I tried this
long time (20 years ?) ago on an a2 with the mouse card's "vbl"
interrupts. The other way I thought it could be done (but never tried)
was finding the vsync signal in the video generator circuit (page 151,
red book, it is one of c13's inputs) and tie it to a game-connector's
switch-n input to be able to poll it reading c06n.

Also, being such a time-critical loop, if not interrupt-driven, there's
not much you can do while in-the-loop, or the whole thing stops being
in-sync... ?

When you say "colored text" I understand you mean the color-killer
circuit is not engaged and the characters appear "colored" as in the
first a2's ? 

Jorge.
(just remembering good-old times)

Bryan Parkoff <nospam@nospam.com> wrote:

>     You may know that low resolution (LGR) has 4 colored text line in the
> bottom.  I have an ability to cause LGR's colored blocks from line 1 through
> line 12 and colored text from line 13 through line 24 on any Apple II+ or
> Apple //e or Apple IIgs.  You may be surprised when it appears to be 
> impossible.
>     I have created a small routine with timed loop by switching C051 and
> C050 back and forth at exact 17030 cycles.  After it reaches 17030 cycles,
> it loops back to the beginning of the routine.  The LGR's colored blocks and
> colored text can be scrolled up or down at fast speed or slow speed.  It
> looks very smooth.
>     Some emulator projects like AppleWin do not do any good, but KEGS is
> almost 90% OK because of flicker.  It has to be free flicker with smooth.  I
> would try to make it smoother.
>     Have you done with this experiment before?
> 
> Bryan Parkoff