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©2008 Advanced Micro Devices, Inc.
OCHI USB 1.1 and EHCI USB 2.0 Controllers
AMD SB600 Register Reference Manual Proprietary Page 61
HcRhDescriptorA - 32 bits - [MEM_Reg : 48h]
Field Name Bits Default HCD HC Description
NDP 7:0 02h R R
NumberDownstreamPorts
These bits specify the number of downstream ports
supported by the Root Hub.
PSM 8 0b RW R
PowerSwitchingMode
This bit is used to specify how the power switching of
the Root Hub ports is controlled. It is implementation-
specific. This field is only valid if the
NoPowerSwitching field is cleared.
0: all ports are powered at the same time.
1: each port is powered individually. This mode
allows port power to be controlled by either the global
switch or per-port switching. If the
PortPowerControlMask bit is set, the port responds
only to port power commands
(Set/ClearPortPower). If the port mask is cleared,
then the port is controlled only by the global power
switch (Set/ClearGlobalPower).
NPS 9 1b RW R
NoPowerSwitching
These bits are used to specify whether power
switching is supported or port are always powered. It
is implementation- specific. When this bit is cleared,
the PowerSwitchingMode specifies global or per-
port switching.
0: Ports are power switched
1: Ports are always powered on when the HC is
powered on
DT 10 0b R R
DeviceType
This bit specifies that the Root Hub is not a
compound device. The Root Hub is not permitted to
be a compound device. This field should always
read/write 0.
OCPM 11 1b RW R
OverCurrentProtectionMode
This bit describes how the overcurrent status for the
Root Hub ports are reported. At reset, this field
should reflect the same mode as
PowerSwitchingMode. This field is valid only if the
NoOverCurrentProtection field is cleared.
0: over-current status is reported collectively for all
downstream ports
1: over-current status is reported on a per-port basis
NOCP 12 0b RW R
NoOverCurrentProtection
This bit describes how the overcurrent status for the
Root Hub ports are reported. When this bit is cleared,
the OverCurrentProtectionMode field specifies
global or per-port reporting.
0: Over-current status is reported collectively for all
downstream ports
1: No overcurrent protection supported
Reserved 23:13 Reserved
POTPGT 31:24 02h RW R
PowerOnToPowerGoodTime
This byte specifies the duration HCD has to wait
before accessing a powered-on port of the Root Hub.
It is implementation-specific. The unit of time is 2 ms.
The duration is calculated as POTPGT * 2 ms.