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A92: TI-ROM
Shawn,
you said before that you would do as much as possible for people to not
mess with the TIs actual ROM. couldn't you just partition a specific
part of FLASH chip to have just ROM, not eraseable not programmable?
how about this notion:
let's say you have 19 pins to the FLASH chip to find the spot in memory
to erase/program (that's .5MB or 512K) and you have the location below
8K (all hypothetical, you can change the values or play around with the
notion). below 8K would mean that the first 6 pins would be 0 and the
other 13 is the 8K selection (the ROM). now, let's say that you don't
want people to mess with this ROM except the TI company when upgrading,
well add an extra pin to the FLASH chip, and if this pin is in the on
position then the calculator will "know" that it's the ti company
messing with the ROM part and not some "hacker." in order to get this
pin in the on position hook it up to another chip (or have it installed
alongside the FLASH chip in 1 package), this chip can be accessed by the
port (or however you want to do it), if the chip registers the correct
"code" it will turn the pin to the FLASH chip on, and the chip can be
changed. of course you could place some sort of timer inside the added
chip, so that the ti company could just set it up to receive for let's
say 100 cycles and after that it turns the pin off. with the pin off
the ROM won't be deleted, on a MOV statement or anything that could
delete the ROM it won't cause errors, but it just won't work (it's like
a safety on a gun, you can pull the trigger, but it won't do anything
unless the safety is off).
just a thought from an 18 year old.
-Rob
p.s. i hope i didn't spell your name wrong.
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