Re: A86: 200 Interupts/Second
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Re: A86: 200 Interupts/Second
In a message dated 97-10-26 00:06:07 EDT, you write:
>
> There has been going around on the lists the idea that the calc
> checks interupts and runs the handlers every 200th of a second. This
> sounds wrong to me; I thought that the whole idea of an interupt was that
> it didn't need to be checked periodicly because the interupt processing
> hardware would get the processors attention when nessecary. I know that
> that's how the PC works and the 8xs can't be much different with a Z80
> inside.
> I heard stories about secrateries outrunning Apple IIs because
> the 6502 doesn't have interupt capabilities and must constantly poll (the
> keyboard) for input. Pat help us, we need someone to clear up the
> confusion. Who's right?
>
> Matthew
>
I may not be Pat, but I think that what it does is this:
When the chip is off, aside from refreshing the RAM, it does nothing. The ON
key, I believe, is connected to something that, when pressed (at least if the
calc is off), will trigger the Non-Maskable Interrupt (NMI) lead. This takes
priority on the cpu, so it restarts at 66H and then starts up.
At least, this is what I've inferred from the Z80 manuals. Anyone
disassembled the contents of 66H?
~Steve
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