USB on-the-go full-speed (OTG_FS) RM0090
1374/1749 RM0090 Rev 18
Figure 405. TRDT max timing case
34.17.8 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.
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0ns 50ns 100ns 150ns 200ns
HCLK
PCLK
tkn_rcvd
dsynced_tkn_rcvd
spr_read
spr_addr
spr_rdata
srcbuf_push
srcbuf_rdata
5 Clocks
D1
A1
D1
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