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Re: Zip Chip programming info / disk image?
Jorge Chamorro Bieling wrote:
Michael J. Mahon <mjmahon@aol.com> wrote:
Not so--RWTS runs in RAM and it must be run slow.
This is why the Zip Chip (and others) start slow mode
whenever a slow slot /DEVSEL address is referenced, and
then maintain slow mode for a heuristically determined
50-or-so milliseconds after a slow slot /DEVSEL reference.
Hmm, about this...
I'm trying to figure out the list of time critical tasks :
-loop to SAVE to a cassette tape.
-loop to LOAD from a cassette tape.
-loop to move the disk II head's stepper.
-loop to write to the disk (every 32 cycles ?, iirc)
...or 36, or 40, or ?? (Not a problem, just must be exact.)
-loop to wait for data coming from the disk (*).
Doesn't have to be exact, as long as it's not too *slow*.
-loop to read the paddles.
-any sound-generating loops.
-??
Any other time-critical loops in slot ROMs, drivers, etc.
UARTS are common cases, and there are many others. I have
programs that drive external stepper motors or servos, and
they use the Apple 1MHz clock to determine pulse timings.
Hard to fix in general, so the "slow mode" escape must always
be provided.
-michael
Music synthesis for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
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