[A83] What does port 4 do?
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[A83] What does port 4 do?
More specifically, what does outputting a value of 77h to it do?
If you look at the beginning of the calculator's rom on the 83+, you'll
notice that first it reads from port 2, and checks to see if its
running on an SE. If it isn't, it maps rom page 1f (the boot page) to
4000-7FFF, and then outputs 77h to port 4. I'm guessing this does
something to the memory mapping on the calculator, because immediately
after that, it jumps 80d5. Does anybody know what this really does?
When I try it, it crashes my calculator.
Does anybody here know anything about this? Thanks for any help anyone
can provide.
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