Xbox 360 Guide button

[Waterbury]

Please is someone knows, explain how a wired Xbox 360 controller is able to power the console from the guide button while the console is in standby.

I read an article on this a few years ago but Google, Yahoo, and this forum's search isn't providing results.    All Google will display for 360 technical is articles dealing with the RROD or processing info.

I believe I read that the power up signal is not carried via USB on power up. Also are the 5V+ lines on the USB ports powered at all times to provide power to the controllers to stay in standby?

[NFG]

The console is never truly 'off' as long as it's plugged in.  Your console and controller are sharing information, so pressing the button just activates the console.

[Waterbury]

I realize that but over USB? Is the USB host controller still awake? Is the device recognized as a valid HID device at connection?  If I remember, the Xbox uses unconventional communications that is not USB related on preboot.

I know the console's fan is on if a wireless controller is connected and needs to be charged, and the power supply's light illuminates green. Otherwise, the PSU's illuminates amber and the console's fan doesnt spin, indicating that the console needs to be in a mid-power state to fully power USB devices.

I'd like the nitty gritty here for a project I'm working on. 

[NFG]

Don't have any nitty gritty for you.  If I had to guess, since they are actively communicating, there's obviously enough juice to power the USB chip but not enough to, for example, charge the batteries.

[Waterbury]

Apparently, the controller receives enough power to power a Saturn controller and microcontroller I have connected. I'm able to power on the console using a special button combination on the Saturn controller. Bitchin'!