82801BA Datasheet, PDF (381/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

USB Controller Registers
Bit
Description
Port Enable/Disable Change—R/WC. For the root hub, this bit gets set only when a port is
disabled due to disconnect on that port or due to the appropriate conditions existing at the EOF2
3
point (See Chapter 11 of the USB Specification).
1 = Port enabled/disabled status has changed.
0 = No change. Software clears this bit by writing a 1 to the bit location.
Port Enabled/Disabled (PORT_EN)—R/W. Ports can be enabled by host software only. Ports can
be disabled by either a fault condition (disconnect event or other fault condition) or by host software.
Note that the bit status does not change until the port state actually changes and that there may be
2
a delay in disabling or enabling a port if there is a transaction currently in progress on the USB.
1 = Enable.
0 = Disable.
Connect Status Change—R/WC. Indicates that a change has occurred in the port’s Current
Connect Status (see bit 0). The hub device sets this bit for any changes to the port device connect
status, even if system software has not cleared a connect status change. If, for example, the
insertion status changes twice before system software has cleared the changed condition, hub
1
hardware will be setting” an already-set bit (i.e., the bit will remain set). However, the hub transfers
the change bit only once when the Host Controller requests a data transfer to the Status Change
endpoint. System software is responsible for determining state change history in such a case.
1 = Change in Current Connect Status.
0 = No change. Software clears this bit by writing a 1 to the bit location.
Current Connect Status—RO. This value reflects the current state of the port, and may not
correspond directly to the event that caused the Connect Status Change bit (Bit 1) to be set.
0
1 = Device is present on port.
0 = No device is present.
82801BA ICH2 and 82801BAM ICH2-M Datasheet
11-15