82801FB Datasheet, PDF (525/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

UHCI Controllers Registers
Bit
Description
Overcurrent Active — RO. This bit is set and cleared by hardware.
10 _{0 = Indicates that the overcurrent pin is inactive (high).}
1 = Indicates that the overcurrent pin is active (low).
Port Reset — R/W.
9
0 = Port is not in Reset.
1 = Port is in Reset. When set, the port is disabled and sends the USB Reset signaling.
Low Speed Device Attached (LS) — RO.
8
0 = Full speed device is attached.
1 = Low speed device is attached to this port.
7 Reserved — RO. Always read as 1.
Resume Detect (RSM_DET) — R/W. Software sets this bit to a 1 to drive resume signaling. The
host controller sets this bit to a 1 if a J-to-K transition is detected for at least 32 microseconds while
the port is in the Suspend state. The ICH6 will then reflect the K-state back onto the bus as long as
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the bit remains a 1, and the port is still in the suspend state (bit 12,2 are ‘11’). Writing a 0 (from 1)
causes the port to send a low speed EOP. This bit will remain a 1 until the EOP has completed.
0 = No resume (K-state) detected/driven on port.
1 = Resume detected/driven on port.
Line Status — RO. These bits reflect the D+ (bit 4) and D– (bit 5) signals lines’ logical levels. These
5:4 bits are used for fault detect and recovery as well as for USB diagnostics. This field is updated at
EOF2 time (See Chapter 11 of the USB Specification).
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
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point (See Chapter 11 of the USB Specification).
0 = No change. Software clears this bit by writing a 1 to the bit location.
1 = Port enabled/disabled status has changed.
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
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a delay in disabling or enabling a port if there is a transaction currently in progress on the USB.
0 = Disable
1 = Enable
Connect Status Change — R/WC. This bit 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
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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.
0 = No change. Software clears this bit by writing a 1 to it.
1 = Change in Current Connect Status.
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
0 = No device is present.
1 = Device is present on port.
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Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
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