82801CA Datasheet, PDF (172/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
5.16 USB 1.1 Controllers (D29:F0, F1 and F2)
The ICH3 contains three USB 1.1 Host Controllers. Each Host Controller includes a root hub with
two separate USB ports each, for a total of six USB ports. The ICH3 Host Controllers support the
standard Universal Host Controller Interface (UHCI) Design Guide, Revision 1.1
(http://developer.intel.com/design/USB/UHCI11D.htm).
Overcurrent detection on all six USB ports is supported. The overcurrent inputs are 5 V-tolerant,
and can be used as GPIs if not needed.
The ICH3’s USB 1.1 controllers are arbitrated as differently than standard PCI devices to improve
arbitration latency.
The USB 1.1 controllers use the Analog Front End (AFE) embedded cell instead of USB I/O
buffers.
5.16.1 Data Structures in Main Memory
This section describes the details of the data structures used to communicate control, status, and
data between software and the ICH3: Frame Lists, Transfer Descriptors, and Queue Heads. Frame
Lists are aligned on 4-KB boundaries. Transfer Descriptors and Queue Heads are aligned on
16-byte boundaries.
5.16.1.1 Frame List Pointer
The frame list pointer contains a link pointer to the first data object to be processed in the frame, as
well as the control bits defined in Table 5-57.
Table 5-57. Frame List Pointer Bit Description
Bit
Description
31:4
Frame List Pointer (FLP). This field contains the address of the first data object to be processed in
the frame and corresponds to memory address signals [31:4], respectively.
3:2 Reserved. These bits must be written as 0.
QH/TD Select (Q). This bit indicates to the hardware whether the item referenced by the link pointer
is a TD (Transfer Descriptor) or a QH (Queue Head). This allows the ICH3 to perform the proper type
1 ^{of processing on the item after it is fetched.}
0 = TD
1 = QH
Terminate (T). This bit indicates to the ICH3 whether the schedule for this frame has valid entries in
it.
0
0 = Pointer is valid (points to a QH or TD).
1 = Empty Frame (pointer is invalid).
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Intel^® 82801CA ICH3-S Datasheet