Author Topic: What happens when a calculator crashes...  (Read 15399 times)

0 Members and 1 Guest are viewing this topic.

Offline Goplat

  • LV5 Advanced (Next: 300)
  • *****
  • Posts: 289
  • Rating: +82/-0
    • View Profile
Re: What happens when a calculator crashes...
« Reply #45 on: March 28, 2011, 06:40:59 pm »
How does the calculator even detect that code is running in the "illegal" area? The only explanation that I can think of is that the last two bits on the address bus (the ones that must be on if code above C000 is being executed) are wired into a trigger that causes the processor to jump to the boot code. In other words, the detection is in the hardware itself.
Most likely it is.  Remember that we are talking about all of this being in the processor.  So the processor knows immediately if the pc is C000h or above.
The original TI-83+ just had a stock Z84C00 processor. The detection there must have been done by outside hardware, probably checking the address and the M1 signal (which is active only on instruction fetches).
Numquam te deseram; numquam te deficiam; numquam circa curram et te desolabo
Numquam te plorare faciam; numquam valedicam; numquam mendacium dicam et te vulnerabo

Offline DrDnar

  • LV7 Elite (Next: 700)
  • *******
  • Posts: 546
  • Rating: +97/-1
    • View Profile
Re: What happens when a calculator crashes...
« Reply #46 on: March 29, 2011, 04:38:16 pm »
Ahh, I didn't know that the Z80 has a signal that's only active on instruction fetch. That would certainly make detecting where the PC is much easier.
"No tools will make a man a skilled workman, or master of defense, nor be of any use to him who has not learned how to handle them, and has never bestowed any attention upon them. . . . Yes, [] the tools which would teach men their own use would be beyond price."—Plato's The Republic, circa 380 BC

Music Man

  • Guest
Re: What happens when a calculator crashes...
« Reply #47 on: March 29, 2011, 05:39:30 pm »
Ahh. Oops. But now I'm curious, what DOES happen? RAM clear? Calc turns off? Do you just remove the batteries for 15 minutes?
You usually don't have to keep batteries out, that's only for rare cases.

That sometimes happens to me