EFM32WG Datasheet, PDF (320/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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6. The application must service the Session Request Detected interrupt and turn on the Port Power bit
by writing the Port Power bit in the Host Port Control and Status register. The PHY indicates port
power-on by detecting a valid VBUS level.
7. When the USB is powered, the device connects, completing the SRP process.
15.4.5.2 B-Device Session Request Protocol
The application must set the SRP-Capable bit in the Core USB Configuration register. This enables the
core to initiate SRP as a B-device. SRP is a means by which the core can request a new session from
the host.
1. To save power, the host suspends and turns off port power when the bus is idle. PHY indicates port
power off by detecting a not valid VBUS level.
The core sets the Early Suspend bit in the Core Interrupt register after 3 ms of bus idleness. Following
this, the core sets the USB Suspend bit in the Core Interrupt register.
The PHY indicates the end of the B-device session by detecting a VBUS level below session valid.
2. PHY to enables the VBUS discharge function to speed up Vbus discharge.
3. The PHY indicates the session’s end by detecting a session end voltage level on VBUS. This is the
initial condition for SRP. The core requires 2 ms of SE0 before initiating SRP.
The application must wait until Vbus discharges to 0.2 V after USB_GOTGCTL.BSESVLD is
deasserted. This discharge time can be obtained from the datasheet.
4. The application initiates SRP by writing the Session Request bit in the OTG Control and Status
register. The core perform data-line pulsing followed by Vbus pulsing.
5. The host detects SRP from either the data-line or Vbus pulsing, and turns on Vbus. The PHY indicates
Vbus power-on by detecting a valid VBUS level.
6. The core performs Vbus pulsing.
The host starts a new session by turning on Vbus, indicating SRP success. The core interrupts the
application by setting the Session Request Success Status Change bit in the OTG Interrupt Status
register. The application reads the Session Request Success bit in the OTG Control and Status
register.
7. When the USB is powered, the core connects, completing the SRP process.
15.4.5.3 A-Device Host Negotiation Protocol
HNP switches the USB host role from the A-device to the B-device. The application must set the HNP-
Capable bit in the Core USB Configuration register to enable the core to perform HNP as an A#device.
1. The core sends the B-device a SetFeature b_hnp_enable descriptor to enable HNP support. The
B-device’s ACK response indicates that the B-device supports HNP. The application must set Host
Set HNP Enable bit in the OTG Control and Status register to indicate to the core that the B-device
supports HNP.
2. When it has finished using the bus, the application suspends by writing the Port Suspend bit in the
Host Port Control and Status register.
3. When the B-device observes a USB suspend, it disconnects, indicating the initial condition for HNP.
The B-device initiates HNP only when it must switch to the host role; otherwise, the bus continues
to be suspended.
The core sets the Host Negotiation Detected interrupt in the OTG Interrupt Status register, indicating
the start of HNP.
The PHY turns off the D+ and D- pulldown resistors to indicate a device role. The PHY enable the D
+ pull-up resistor indicates a connect for B-device.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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