82801DB Datasheet, PDF (204/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
5.17.8.3
5.17.8.4
Device Disconnects
Section 4.2 of the Enhanced Host Controller Interface (EHCI) for Universal Serial Bus
Specification describes the details of handling Device Connects. There are three general scenarios
that are summarized below.
1. Configure Flag = 0 and the device is disconnected
— In this case, the USB UHCI controller is the owner of the port both before and after the
disconnect occurs. The EHC (except for the port-routing logic) never sees a device
attached. The UHCI driver handles disconnection process.
2. Configure Flag = 1 and a USB Full-speed/Low-speed-capable Device is disconnected
— In this case, the USB UHCI controller is the owner of the port before the disconnect
occurs. The disconnect is reported by the USB UHCI controller and serviced by the
associated UHCI driver. The port-routing logic in the EHC cluster forces the Port Owner
bit to 0, indicating that the EHC owns the unconnected port.
3. Configure Flag = 1 and a USB High-speed-capable Device is disconnected
— In this case, the USB EHCI controller is the owner of the port before, and remains the
owner after, the disconnect occurs. The EHCI hardware and driver handle the
disconnection process. The USB UHCI controller never sees a device attached.
Effect of Resets on Port-Routing Logic
As mentioned above, the Port Routing logic is implemented in the Suspend power well so that re-
enumeration and re-mapping of the USB ports is not required following entering and exiting a
system sleep state in which the core power is turned off.
Reset Event
Suspend Well Reset
Core Well Reset
D3-to-D0 Reset
HCRESET
Effect on Configure Flag
cleared (0)
no effect
no effect
cleared (0)
Effect on Port Owner Bits
set (1)
no effect
no effect
set (1)
5.17.9
USB 2.0 Legacy Keyboard Operation
The ICH4 must support the possibility of a keyboard downstream from either a USB UHCI or a
USB EHCI port. The description of the legacy keyboard support is unchanged from USB UHCI
(See Section 5.16.8).
The EHC provides the basic ability to generate SMIs on an interrupt event, along with more
sophisticated control of the generation of SMIs.
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Intel^® 82801DB ICH4 Datasheet