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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
415
USB 2.0 Host Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
9.14.2.4
Port Power
The Port Power Control (PPC) bit in the HCSPARAMS register indicates whether the
USB 2.0 host controller has port power control (See
EHCI Compliant with Extensions” on page 370
). When this bit is a zero, then the host
controller does not support software control of port power switches. When in this
configuration, the port power is always available and the companion host controllers
must implement functionality consistent with port power always on. When the PPC bit is
a one, then the host controller implementation includes port power switches. Each
available switch has an output enable, which is referred to in this discussion as
PortPowerOutputEnable (PPE). PPE is controlled based on the state of the combination
bits PPC bit, EHCI Configured (CF)-bit and individual Port Power (PP) bits.
“Port Power Enable Control Rules” on page 415
illustrates the summary behavioral
model.
9.14.2.5
Port Reporting Over-Current
Host controllers are by definition power providers on USB. Whether the ports are
considered high- or low-powered is a platform implementation issue. Each EHCI
PORTSC register has an over-current status and over-current change bit. The
functionality of these bits is specified in the USB Specification Revision 2.0.
The over current detection and limiting logic usually resides outside the host controller
logic. This logic may be associated with one or more ports. When this logic detects an
over-current condition it is made available to both the companion and EHCI ports. The
effect of an over-current status on a companion host controller port is beyond the
scope of this document. The over-current condition effects the following bits in the
PORTSC register on the EHCI port:
• Over-current Active bits are set to a one. When the over-current condition goes
away, the Over-current Active bit will transition from a one to a zero.
Table 169.
Port Power Enable Control Rules
CF
CHC
(PP)
EHC
(PP)
Owner
PPE
Description
0
0
X
CHC
0
When the EHCI controller has not been configured, the
port is owned by the companion host controller. When
the companion HC's port power select is off, then the
port power is off.
0
1
X
CHC
1
Similar to previous entry. When the companion HC's
port power select is on, then the port power is on.
1
0 0 CHC 0
Port owner has port power turned off, the power to
port is off.
1
0 0 EHC 0
Port owner has port power turned off, the power to
port is off.
1
0
1
EHC
1
Port owner has port power on, so power to port is on.
1
0 1 CHC 1
If either HC has port power turned on, the power to
the port is on.
1
1 0 EHC 1
If either HC has port power turned on, the power to
the port is on.
1
1
0
CHC
1
Port owner has port power on, so power to port is on.
1
1
1
CHC
1
Port owner has port power on, so power to port is on.
1
1
1
EHC
1
Port owner has port power on, so power to port is on.
Notes:
1.
PPE (Port Power Enable). This bit actually turns on the port power switch (if one exists).
2.
CHC (Companion Host Controller).
3.
EHC (EHCI Host Controller).