Universal Serial Bus OTG Controller
UG0331 User Guide Revision 15.0
296
3.
Flushes all endpoint FIFOs
4.
Clears all control/status registers
5.
Enables all endpoint interrupts
6.
Generates a reset interrupt
If the HS Enab bit in
is set, the USB controller tries to negotiate for high
speed operation.
Whether or not the high speed operation is selected, is indicated by the HS mode bit in POWER_REG.
When the application software driving the USB controller receives a reset interrupt, it should close any
open pipes and wait for the bus enumeration to begin.
10.2.3.2.2 Host Mode
If the reset bit in POWER_REG is set while the USB controller is in Host mode, the USB controller
generates reset signaling on the bus. If the HS Enab bit in POWER_REG is set, it tries to negotiate for a
high speed operation.
The Cortex-M3 processor or fabric master should keep the reset bit set for at least 20 ms to ensure the
correct resetting of the target device.
After the Cortex-M3 processor or fabric master clears the bit, the USB controller starts it’s frame counter
and transaction scheduler. Whether a high speed operation is selected, is indicated by the HS mode bit
of
10.2.3.3 USB OTG Controller: Suspend/Resume Operations
With the introduction of link power management (LPM), there are two basic methods for the USB
controller to be suspended and resumed. These two methods are demonstrated in the basic LPM
transaction diagram as shown in the following figure
.
Figure 145 •
LPM State Transition Diagram
The procedure in which the controller is suspended and resumed depends on whether the controller is
operating as a device (peripheral) or as a host, and the method of suspend desired.
10.2.3.3.1 Suspend/Resume by Inactivity on the USB Bus (L0 to L2 State Transition)
Suspend/Resume when Operating as a Peripheral
•
Entry into Suspend Mode:
When operating as a peripheral, the USB controller monitors activity on
the USB and when no activity has occurred for 3 ms, it goes into Suspend mode. If the Suspend
interrupt
has been enabled, an interrupt is generated at this
time. The SUSPENDM output also goes low (if enabled).
At this point, the POWERDWN signal is also asserted to indicate that the application may save
power by stopping CLK.
Disconnect
Power Loss
and Disable
Remote Wake
Enabled by LPM
Transaction
Resume/Remote Wake
Signaling Levels - Same as L2 to L0
Timing - LPM Specific
Resume/Remote Wake
Signaling Levels - Defined by USB v2.0
Timing - Defined by USB v2.0
ACK and Response to LPM
L1
L3
L0
L2
Reset and Enable
3 ms of Inactivity
Remote Wake
Enabled by
Set Feature