[A83] Re: Turning calc off
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[A83] Re: Turning calc off
So nothing needs to be done with port $10 to turn off or on the lcd???
jeff
----- Original Message -----
From: "Tijl Coosemans" <tijl@ulyssis.org>
To: <assembly-83@lists.ticalc.org>
Sent: Friday, January 17, 2003 7:33 AM
Subject: [A83] Re: Turning calc off
> On Thu, 16 Jan 2003 20:27:14 -0600, Grant Miller wrote:
>
> > Any interrupt will re-enable them (actually, I think they might be
> > re-enabled in the interrupt handler) At any rate, when you press on,
> > they get re-enabled.
>
> Things are slightly more complicated than that.
>
> You can only turn off interrupts with "di". Without a "di" every
> interrupt is caught and an interrupt routine is called. What you can
> change though (in case of maskable interrupts, which all interrupts are
> on these calcs) is the interrupt mask, or in other words, change the
> ability of the TIOS to know what sort of interrupt happened.
>
> What you do with "out(3),1" is setting this mask (and turning off the
> lcd (bit 3)), allowing on key interrupts to be detected, but not timer
> interrupts. So when a timer interrupt occurs, the interrupt routine does
> nothing (keys, cursor, busy indicator, apd timer...) and just returns to
> the main program flow. When an on key interrupt occurs the state of port
> 3 will be reset, turning on the lcd and timer interrupts.
>
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