ST STM32F40 Series User Manual

RM0090 USB on-the-go high-speed (OTG_HS)
Doc ID 018909 Rev 4 1312/1422
B-device session request protocol
The application must set the SRP-capable bit in the Core USB configuration register. This
enables the OTG_HS controller to initiate SRP as a B-device. SRP is a means by which the
OTG_HS controller can request a new session from the host.
Figure 400. B-device SRP
1. VBUS_VALID = V
BUS
valid signal from PHY
B_VALID = B-device valid session to PHY
DISCHRG_VBUS = discharge signal to PHY
SESS_END = session end signal to PHY
CHRG_VBUS = charge V
BUS
signal to PHY
DP = Data plus line
DM = Data minus line
1. To save power, the host suspends and turns off port power when the bus is idle.
The OTG_HS controller sets the early suspend bit in the Core interrupt register after 3
ms of bus idleness. Following this, the OTG_HS controller sets the USB suspend bit in
the Core interrupt register.
The OTG_HS controller informs the PHY to discharge V
BUS
.
2. The PHY indicates the session’s end to the device. This is the initial condition for SRP.
The OTG_HS controller requires 2 ms of SE0 before initiating SRP.
For a USB 1.1 full-speed serial transceiver, the application must wait until V
BUS
discharges to 0.2 V after BSVLD (in OTG_HS_GOTGCTL) is deasserted. This
ai1568b2
VBUS_VALID
B_VALID
DISCHRG_VBUS
SESS_END
OTG_HS_FS_DP
OTG_HS_FS_DM
CHRG_VBUS
Suspend
Data line pulsing Connect
V
BUS
pulsing
1
6
2
3
4
5 8
7
Low

ST STM32F40 Series Specifications

General

Brand	ST
Model	STM32F40 Series
Category	Microcontrollers
Language	English