Jeff Strickland wrote:
> "JD" <> wrote in message
> news:4b220f72$0$2535$...
>> Peter Jason wrote:
>>> Why?
>>>
>>> Please help, P
>> Hi there
>>
>> As Jeff and Paul say the drive may be in use if you built it yourself
>> connecting the power button to the IO panel you may have put the "PWR
>> Switch" wires in the wrong way round which will cause the light to come on
>> when the drive is NOT in use and off when it is.
>>
>> JD
>
>
> While is certainly possible that the lights are switched, if it wasw true
> that they were switched, then the Power light should be blinking to indicate
> that the HDD is being read.
>
> The HDD light is supposed to blink on a random schedule as data is being
> read, if the light is on continuously then something is making a call to the
> HDD causing it to read data all of the time. If the HDD lighth is on steady
> and the Power light is blinking, then my money is on the connectors being
> switched.
>
> If the connectors are switched and the machine is Home Built, maybe one
> should give consideration to not building any more computers.
>
There are a couple ways for the LED signal to be created. You could
use the status signal right off the IDE ribbon cable (with appropriate
buffering). Or, the status signal could be coming from the Southbridge
itself, partially under software control. In the case of my LED, which
turns on steady while my screensaver is running, I suspect the LED state is being
affected by something the driver is doing. And I've tested it, by
moving the mouse (to get rid of the screensaver), then double clicking a disk
icon to get some hard drive activity. The LED actually blinks off, then
comes back on, as if an XOR gate is present in the circuit and the
activity state of the LED has been changed (normally ON, blink OFF).
Roughly ten seconds after the screen saver has stopped, the LED goes out,
and returns to blinking on in response disk activity. So my problem is
related to something involving "driver" / "power management state" /
"perhaps Southbridge".
We really need a more detailed description of what the OP's LED is doing,
to decide what it is. If the motherboard has a manual, with PANEL pinout
and named signals, it may be possible to guess at whether you can
arrange a LED on some set of pins, to stay on.
For the LED to work properly, there has to be a series resistor in
series in the circuit, to limit current flow to a safe value. I don't
believe that resistor is on the computer case side. It is part of the
LED driver on the motherboard. If someone connects the LED cable between
raw +5V and GND, the LED would burn out. For the LED to remain lit
constantly, it would preferably be on a circuit with resistor in
series. So there are some limits as to how many pin combinations
on the PANEL header, can provide just the right ingredients.
+5V --- resistor ----X X---GND (Panel pins to make a steady LED)
If you connected a LED to the RESET pin pair, that would provide a pullup
circuit similar to the drawing. And, the LED would pull the circuit
down to Vfb of the LED, perhaps still sufficient to not be interpreted
as logic 0, and lighting the LED at the same time. I doubt the
pullup resistor value on the RESET pin pair, is the right value to
make the LED glow at normal brilliance. So there are plenty of
nuances, that if someone describes the intensity, when the LED comes
on or goes off, you could guess at where it is connected.
In my case, my symptoms are bizarre enough, to need software to get
involved. My symptoms are not consistent with a wiring error, and look
more like the activity state of my LED gets flipped during a Power
Management state change.
Paul
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