Re: A89: Check sum problem Really need help
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Re: A89: Check sum problem Really need help
>
>>The TI-89 will tell you when the batteries get low, and when they get very
>>low, but besides that there is no way to tell. However, if the calc can
tell
>>you when the batteries are low it might be possible to write a battery
level
>>program.
>>
>>Daniel Imfeld
>
>I looked into the issue and don't really think that would be possible any
>more. I suspect that the 89 had a low battery inturupt, not just a ROM
>function that gets called every so many clock cycles. So without changing
>the actual hardware you couldn't really change the battery alert system.
>Computers have a similar inturupt that occurs when the power is failing.
>
> --Nate
There's a similar thread to this on the assembly-86 list. The 86 ROM tests
to see if the time in which the mask runs out on the keypad port is shorter
than a predetermined number of CPU clock cycles (if it is, you're low on
batteries), and this is probably similar to what the 89 does. You can make
this into a percentage, but the problem is that you have to read from the
port and increment a counter within a loop, and the longer that it takes you
to do so, the less accuracy. You might be able to use the interrupt as
well, if the interrupt clock is independent of the 68k processor as it is on
the z80.
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