Re: LZ: Now that the battery problem is settled...
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Re: LZ: Now that the battery problem is settled...
TGaArdvark@aol.com wrote:
>
> In order to reset your TI85 (all ROM versions, I don't know about other
> calculators), all you need to do is REMOVE ONE AAA BATTERY AND PRESS [ON] 10
> TIMES. This will _ALWAYS_ work because it's hard-wired to the board and
> cannot "crash".
>
> My main hypothesis is that they use a small capacitor, so you might be able
> to hold down the [ON] key for a few seconds with the same result. I have not
> tested this because I don't currently have access to my graphlink (or any
> other) and don't want to clear my calculator's memory.
Actually, that's not it. Maybe kinda, but not _exactly_. As was
mentioned in the earlier posting, when the Z80 reaches a HALT
instruction, it pulls its /HALT pin (output) low, which then activates a
circuit that enables the button cell. The reason the calc resets when
you press [ON] with the AAAs out is because there _is_ a tiny remaining
charge in a capicator which keeps the RAM and Z80 on. When you _do_
press [ON], the HALT instruction is no longer active; the /HALT pin on
the Z80 then goes high again, disabling the button cell. When this
happens, the calc expects the AAAs to be there, but they're not...
Now do you see what's happening?
Cheers,
--
~Keith
TSK3000@Prodigy.Net
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