Re: A83: Time on TI-83

To: <assembly-83@lists.ticalc.org>
Subject: Re: A83: Time on TI-83
From: "Justin Karneges" <jgkarneges@ucdavis.edu>
Date: Tue, 10 Nov 1998 18:20:45 -0800
Delivered-To: assembly-83-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-83@lists.ticalc.org


>> Wouldn't a counting loop like that consume ALOT of power?  Remember, the
Z80
>> only uses little power when executing a HALT.  If you could figure out a
way
>> to let the timer interrupt get called while the calc was off, you could
>> update the clock in that like you would when it was on, just don't print
the
>> time if it's off.
>
>the difference in batteryconsumption is in the scale of mA when running and
uA
>when in halt.. that is 1000times.. quite a lot...   And one more _big_
problem
>about time..  The oscillator circuit in the Ti83 is Very simple..  it is
just a
>RC-oscilator if I'm not mistaken.. (that is on Capacitator and one
Resistor) and
>its frequency (and thus the speed of the z80) varies depending on
temperature
>and batterypower..  very hard to make a clock very exact..
>
>//Olle
>

You can still make a clock under those conditions.  The 200 times a second
interrupt is (so I've heard) not always 200 times a second.  It depends on
battery and temp.  Now, since the time it takes to execute a Z80 instruction
is static (go find a z80 instruction table with the number of nanoseconds
per instruction listed), you could "figure out" the rate of the interrupt
based on how many "nop"s or whatever that you were able to execute between
interrupts.  Anyways, I'm sure something could be done.  Once you know the
interrupt rate, you can base everything on that.  I know that a program
called "sysmon" for the TI-86 uses this method to display a battery gauge on
your screen.

-Justin

Follow-Ups:

Re: A83: Time on TI-83

From: Olle Hedman <oh@hem.passagen.se>