Table 18.21 Power Switching Configurations - Hitachi HD64465 User Manual

Hub Control
The HC states defined in HC Register Summary section also reflect the hub state. For example,
when the HC is suspended, U
U R , the hub generates the appropriate bus signaling. U
SB ESUME
following sections describe hub and bus related controls and status.
1) Power Switching
The hub controls power to the downstream ports. USB Host Controller implement global
power control, which means that all port power status, PortPowerStatus, is controlled by
Set/ClearGlobalPower commands. Individual port power switching as well as no power
switching modes are also implemented. Table 18-21 shows the power switching configurations
in the descriptor registers. The global power switch is connected to PWREN.

Table 18.21 Power Switching Configurations

Mode
No Switching
Global Switching
Individual Port Switching
Global Switch in Individual
Switching Mode
2) Over-Current Protection
Over-Current is reported on a global basis. Input pin OVRCUR is read directly through
OverCurrentIndicator in HcRhStatus. Over-current mode is configured in HcRhDescriptorA
by NoOverCurrentProtection and OverCurrentProtectionMode. When in individual over-
current mode, OVRCUR status is reported through the PortOverCurrentIndicator in
HcRhPortStatus for test purposes.
When an over-current condition occurs OverCurrentIndicatorChange is set and power is
disabled. If port power is not switched (NoPowerSwitch), the port power status is not affected
by an over-current condition.
3) Reset
When the HC is in the U
Root Hub and SIE logic. The only logic not affected by this reset is the Root Hub Descriptor
registers which are configured by the system and not the HCD and, therefore, are reset only by
the hardware reset (PCIRST#).
4) Suspend
When the HC is in the U
cease packet requests which effectively removes all bus activity through the hub and ports.
U S also disables the USB 12 MHz clock.
SB USPEND
S , the Root Hub is suspended. When the HC is in
SB USPEND
NoPowerSwitching
1
0
0
0
R state, the entire USB interface is reset. This includes the
SB ESET
S state, all control and status is unaffected. The HC will
SB USPEND
R resets the Root Hub. The
SB ESET
PowerSwitchingMode
-
0
1
1
Rev. 3.0, 03/01, page 311 of 390
PortPowerControlMask
-
-
1
0