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Subject: Re: ATA - USE_POWEROFF vs USE_SLEEP
From: Andrew Jamieson (ajamiesn_at_optusnet.com.au)
Date: 2002-09-11


> > On another note - you mention tri-stating the ATA bus during
> > sleep; did you try it with the bus driven (to some idle state)?
>
> I can't drive it, /G is controlled by a chip select signal from the
address
> decoder in the CPU. And the data direction is controlled by the /RD
> signal...
>

Godamn. I musta been tired last night. And even though you could
technically switch the CS decoder off for this pin, you'd be left with a
hobbled bus during reads from any other location. My bad.

> > From what i understand of the ATA interface, the bus remains
> > active during sleep. You'd want to tri-state it for power-off,
> > but not sleep.
>
> Ok , then it may not be what causes the extra current draw. What could it
be
> then...?
>

Very good question. Now I've had some time to think of it, the ATA bus is
left in highZ all the time, so if it was floating CMOS inputs, I'd expect
this to raise the current draw across the bar. I dunno.

> > Floating CMOS inputs could explain the extra
> > current draw.
>
> That's what I have been thinking. But I'm definitely not sure...
>
> /Linus

That makes two of us. As I said, I'll check out my AJB on the weekend to
see if there is a FET switch I missed the first time 'round (god knows
there's alot of other stuff I missed).

I'll leave all you coder guys alone 'til then :)

A



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