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5) Resume
When the HC is in U
but not selectively suspended ports. Signaling is maintained until the HC leaves U
A trailing LS EOP is used to terminate the resume. After the Resume is removed, bus activity
returns to normal.
6) Wakeup Events
If the HC is in U
SB
the Root Hub and HC. A remote wakeup generates a ResumeDetected interrupt and a
transition to the U
A K-state(resume) at an enabled port.
A port connect/disconnect detection and DeviceRemoteWakeupEnable is set.
A port resume is in progress at a selectively suspended port.
When the Root Hub forces a transition to U
same as that described in HC Register Summary section.
7) Low Speed EOP
The Root Hub must generate LS EOPs during normal operation with each SOF and after
exiting U
R
SB
ESUME
times of the J-state.
The LS keep-alive EOP is initiated in parallel to the SOF transaction when the Frame Manager
generates an SOF request. The pulse is guaranteed to complete prior to any attempted access to
the LS device.
The resume LS EOP prevents any other bus activity from the SIE.
Port Control
The Port is responsible for all activity associated with driving and monitoring bus states. The HCD
controls this behavior through the register command interface.
1) Connect/Disconnect
Ports are responsible for detecting when devices are attached and disconnected. A port must
have power enabled before any bus state evaluation may occur. Thus, a port is always
disconnected following a reset (not a port reset). An unconnected port is characterized by a
SE0 bus state. A FS connection is characterized by a differential '1'. A LS connection is
characterized by a differential '0'.
CurrentConnectStatus reports the connection state of the port. When the port is not driving
the bus, a connect event is detected by non-SE0 state on the bus for 30 bit times (2.5 us). A
disconnect event is a SE0 on the bus for 30 bit times. Each time an event is detected and
CurrentConnectStatus changes, ConnectStatusChange is set. LowSpeedDeviceAttached is
set if the connect state is LS when a connect event is detected. When a LS device is attached,
the transmitted and received data bit stream is inverted (J=0,K=1). This allows all data to be
processed through the SIE at the FS state definition.
Rev. 3.0, 03/01, page 312 of 390
R
, the resume signal, K-state, is broadcast to all enabled ports,
SB
ESUME
S
, status changes in the hub or ports create wakeup conditions for
USPEND
R
state. A remote wakeup is defined as follows.
SB
ESUME
to U
O
SB
PERATIONAL
R
state, the resulting bus activity is the
SB
ESUME
. The EOP is 16 FS bit times of SE0 and 8 FS bit
R
.
SB
ESUME
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