Hmm. That was part of my question :) It seems to me that the -cartridge-
needs to remember what state it is in in order to properly map the correct
slice to the correct segment. From my original question:
The way I'm seeing it, if someone did a:
LDA $1FE0
LDA $1FE8
LDA $1FF0
then slice 0 (0000-03FF) will be mapped to each of the 3 segments
(1000-13FF for segment #0, 1400-17FF for segment #1, 1800-1BFF for segment
#2). Why would something like that ever want to be done?
And then, the memory map will stay as above until someone later on in the
code does a LDA $1FE9, for example, and then slice 1 (0400-07FF) would be
mapped into segment #1 (keeping the mappings of segment #0 and segment #2
untouched)?
The cartridge would need to know which slices are mapped to which segment
at any given point in time, since it will send back different code to the
system depending on which slice is actually mapped into the segment, right?
This sounds complicated to me from a cartridge point-of-view, especially if
you think in 1982 terms, since there will need to be some state machine
circuitry or something to keep track of the state of each segment (so
probably 9 bits of storage, 3 bits to specify the current slice 0-7 for
each segment).
Maybe another way to ask this is: When programming, once a slice is mapped
into a segment (with LDA to one of the hot-spots, LDA $1FE0 for example),
that memory map will stay the same until another slice is later loaded into
the segment (LDA $1FE1, for example).
Am I understanding this properly?
I know there are some guys on the list that have successfully supported E0
in their Flash/RAM carts, etc. so speak up :)
Joe
At 09:30 AM 4/25/2003, Thomas Jentzsch wrote:
Joe wrote:
> Can someone clarify this for me?
Hm, I don't understand your problem.
With standard Atari bankswitching you don't have to remember which segment
you are in (since there is only one) but you are very inflexible.
With E0 bankswitching you are very flexible and the more flexible you use
the segments the more you have to keep track of what slice is in which
segment. Normally you won't swap slices too much, e.g. keeping three
segments constant all the time and only swap the fourth one to use
different data (or code) for different levels.
What that your question?
Have fun!
Thomas
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