Figure 495. Usb_Fs Peripheral-Only Connection; Srp-Capable Peripheral - ST STM32L4x6 Reference Manual

USB on-the-go full-speed (OTG_FS)
1. Use a regulator to build a bus-powered device.
43.6.1

SRP-capable peripheral

The SRP capable bit in the Global USB configuration register (SRPCAP bit in
OTG_GUSBCFG) enables the OTG_FS to support the session request protocol (SRP). In
this way, it allows the remote A-device to save power by switching off V
session is suspended.
The SRP peripheral mode program model is described in detail in the
request protocol
43.6.2 Peripheral states
Powered state
The V
BUS
to enter the powered state (see USB2.0 par9.1). The OTG_FS then automatically connects
the DP pull-up resistor to signal full-speed device connection to the host and generates the
session request interrupt (SRQINT bit in OTG_GINTSTS) to notify the powered state.
The V
BUS
operations. If a drop in V
because of a power disturbance or if the host port has been switched off), the OTG_FS
automatically disconnects and the session end detected (SEDET bit in OTG_GOTGINT)
interrupt is generated to notify that the OTG_FS has exited the powered state.
In the powered state, the OTG_FS expects to receive some reset signaling from the host.
No other USB operation is possible. When a reset signaling is received the reset detected
interrupt (USBRST in OTG_GINTSTS) is generated. When the reset signaling is complete,
the enumeration done interrupt (ENUMDNE bit in OTG_GINTSTS) is generated and the
OTG_FS enters the Default state.
1502/1693

Figure 495. USB_FS peripheral-only connection

section.
input detects the B-Session valid voltage by which the USB peripheral is allowed
input also ensures that valid V
below B-session valid happens to be detected (for instance
BUS
DocID024597 Rev 3
levels are supplied by the host during USB
BUS
RM0351
while the USB
BUS
B-device session