[A83] Re: NMI
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[A83] Re: NMI
On Saturday 30 March 2002 15:44, you wrote:
> Of course it turns off. But how? Normally the TIOS handles
> the "off" state, which is performed with setting some
> values to something else I presume. When you take out the
> batteries while "on", it is like a reset without the normal
> software shutdown process. How does the TIOS overcome the
> problems arising from such an extraordinary event?
>
> Or the "off" state is not indicated in the RAM, only
> through ports?
I've been thinking about this myself a long while back. On the 83- at least,
I think bit 4 and/or 6 of port 2 have something to do with this. If I recall
correctly, during an on-key interrupt, the calc checks (one of) these bits
and resets the ram when it's set. I don't know what exactly their purpose is,
but they probably get set somehow when you pull out batteries while the calc
is still on.
References: