RM0090: Reference manual - STMicroelectronics

USB on-the-go high-speed (OTG_HS) RM0090
discharge time can be obtained from the transceiver vendor and varies from one
transceiver to another.
3. The USB OTG core informs the PHY to speed up VBUS discharge.
4. The application initiates SRP by writing the session request bit in the OTG Control and
status register. The OTG_HS controller perform data-line pulsing followed by VBUS pulsing.
5. The host detects SRP from either the data-line or VBUS pulsing, and turns on VBUS .
The PHY indicates VBUS power-on to the device.
6. The OTG_HS controller performs VBUS pulsing.
The host starts a new session by turning on VBUS , indicating SRP success. The
OTG_HS controller interrupts the application by setting the session request success
status change bit in the OTG interrupt status register. The application reads the session
request success bit in the OTG control and status register.
7. When the USB is powered, the OTG_HS controller connects, completing the SRP
process.
A-device host negotiation protocol
HNP switches the USB host role from the A-device to the B-device. The application must set
the HNP-capable bit in the Core USB configuration register to enable the OTG_HS
controller to perform HNP as an A-device.
Figure 400. A-device HNP
OTG core
DP
DM
1
DPPULLDOWN
DMPULLDOWN
Host Device Host
Suspend 2
1. DPPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DP line inside the PHY.
DMPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DM line inside the PHY.
1. The OTG_HS controller sends the B-device a SetFeature b_hnp_enable descriptor to
enable HNP support. The B-device’s ACK response indicates that the B-device
supports HNP. The application must set host Set HNP Enable bit in the OTG Control
1309/1416 Doc ID 018909 Rev 3
3
4 5
Reset
6
Traffic 7
Traffic
8
Connect
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