UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
584 of 1269
NXP Semiconductors
UM10503
Chapter 23: LPC43xx USB0 Host/Device/OTG controller
external event could clear the suspend bit and start the transceiver clock running again.
The software can then initiate a resume by setting the resume bit in the port controller, or
force a reconnect by setting the reset bit in the port controller.
If all devices have disconnected from the host, the host can go into a low power mode by
the software setting the suspend bit. From the disconnect-Suspended state a connect
event can start the transceiver clock and interrupt the software. The software then needs
to set the reset bit to start the connect process.
23.11.4 Susp_CTRL module
The SUSP_CTRL module implements the power management logic of the USB block. It
controls the suspend input of the transceiver. Asserting this suspend signal
(PORTSC1.PHCD bit) will put the transceiver in suspend mode and the 480 MHz clock or
the 60 MHz clock will be switched off.
In suspend mode, the transceiver will raise an output signal indicating that the PLL
generating the 480 MHz clock can be switched off.
For USB0 this signal is connected to event #9 (USB0_L) in the event router (see
). Software should check for this signal to be HIGH before stopping the USB PLL
and putting the chip in low power mode. Note that the event router block doesn't support a
raw pin status register hence HIGH level detection should be configured for this pin to
detect when to turn the PLL off. Similarly, to detect resume signaling to leave the low
power state, software should configure this pin to detect a LOW-level in the event router.
The SUSP_CTRL module also generates an output signal indicating whether the AHB
clock is needed or not. If not, the AHB clock is allowed to be switched off or reduced in
frequency in order to save power.
For USB0, this signal is used to turn off the AHB clock to USB block.
The core will enter the low power state if:
•
Software sets the PORTSC1.PHCD bit.
When operating in host mode, the core will leave the low power state on one of the
following conditions:
•
software clears the PORTSC1.PHCD bit
•
a device is connected and the PORTSC1.WKCN bit is set
•
a device is disconnected an the PORTSC1.WKDC bit is set
•
an over-current condition occurs and the PORTSC1.WKOC bit is set
•
a remote wake-up from the attached device occurs (when USB bus was in suspend)
•
a change on vbusvalid occurs (= VBUS threshold at 4.4 V is crossed)
•
a change on bvalid occurs (=VBUS threshold at 4.0 V is crossed).
When operating in device mode, the core will leave the low power state on one of the
following conditions:
•
software clears the PORTSC1.PHCD bit.
•
a change on the USB data lines (dp/dm) occurs.