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:
> > 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 press [ON], the HALT instruction is no longer active; the /HALT pin on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?
>
> Incorrect. What I'm talking about has NOTHING to do with the Z80 and never
> involves the processor at all. It's hard-wired.
HOW is it hard wired? Open up the calc. There's 3 chips only.
pressing the ON key 10 times would require a counter circuit (on an
IC). Now the capicator thingy... that's a bit more likely.
BTW: the Z80 _MUST_ be kept ON ALL THE TIME, or it WILL NOT be able to
detect the interrupt caused by the ON key. AND there's NO OTHER WAY to
turn on the calc. Shutting off the Z80 would cause it to start at
address $0000, and re-initialize the calc EVERY TIME YOU TURNED IT ON;
and NO, the mem is NOT reset every time you turn it on. :)
> >> 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".
If you find a circuit that IS hard-wired to the PCB, then I'll completly
believe you. For now, though, I believe what's typed at the top... ^
Cheers,
--
~Keith
TSK3000@Prodigy.Net
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