Otg Programming Model; Figure 393. A-Device Srp - ST STM32F207 Series Reference Manual

RM0033
30.13.9

OTG programming model

The OTG_HS controller is an OTG device supporting HNP and SRP. When the core is
connected to an "A" plug, it is referred to as an A-device. When the core is connected to a
"B" plug it is referred to as a B-device. In host mode, the OTG_HS controller turns off V
to conserve power. SRP is a method by which the B-device signals the A-device to turn on
V power. A device must perform both data-line pulsing and V
BUS
detect either data-line pulsing or V
device negotiates and switches to host role. In Negotiated mode after HNP, the B-device
suspends the bus and reverts to the device role.
A-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 detect SRP as an A-device.
VBUS_VALID
OTG_HS_FS_DP
OTG_HS_FS_DM
1. DRV_VBUS = V
VBUS_VALID = V
A_VALID = A-device V
DP = Data plus line
DM = Data minus line
Suspend
1
DRV_VBUS
A_VALID
Low
drive signal to the PHY
BUS
valid signal from PHY
BUS
level signal to PHY
BUS
USB on-the-go high-speed (OTG_HS)
pulsing for SRP. HNP is a method by which the B-
BUS

Figure 393. A-device SRP

2
4
Data line pulsing
3
RM0033 Rev 9
pulsing, but a host can
BUS
6
5
V pulsing
BUS
7
Connect
ai15681b
1255/1381
BUS
1260