STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

USB on-the-go full-speed (OTG_FS)
RM0008
Figure 279. TRDT max timing case
0ns 50ns 100ns 150ns 200ns
HCLK
1 2 3 4 5 6 7 8
PCLK
tkn_rcvd
dsynced_tkn_rcvd
spr_read
spr_addr
A1
spr_rdata
D1
srcbuf_push
srcbuf_rdata
D1
5 Clocks
ai15680
26.15.8 OTG programming model
The OTG_FS 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_FS controller turns off V BUS
to conserve power. SRP is a method by which the B-device signals the A-device to turn on
V BUS power. A device must perform both data-line pulsing and V BUS pulsing, but a host can
detect either data-line pulsing or V BUS pulsing for SRP. HNP is a method by which the B-
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_FS controller to detect SRP as an A-device.
830/995 Doc ID 13902 Rev 9