Embedded Full-Speed Otg Phy; Otg Dual-Role Device; Id Line Detection; Hnp Dual Role Device - ST STM32F207 Series Reference Manual

USB on-the-go high-speed (OTG_HS)
30.3.3

Embedded Full-speed OTG PHY

The full-speed OTG PHY includes the following components:
•
FS/LS transceiver module used by both host and Device. It directly drives transmission
and reception on the single-ended USB lines.
•
Integrated ID pull-up resistor used to sample the ID line for A/B Device identification.
•
DP/DM integrated pull-up and pull-down resistors controlled by the OTG_HS core
depending on the current role of the device. As a peripheral, it enables the DP pull-up
resistor to signal full-speed peripheral connections as soon as V
a valid level (B-session valid). In host mode, pull-down resistors are enabled on both
DP/DM. Pull-up and pull-down resistors are dynamically switched when the peripheral
role is changed via the host negotiation protocol (HNP).
•
Pull-up/pull-down resistor ECN circuit
The DP pull-up consists of 2 resistors controlled separately from the OTG_HS as per
the resistor Engineering Change Notice applied to USB Rev2.0. The dynamic trimming
of the DP pull-up strength allows to achieve a better noise rejection and Tx/Rx signal
quality.
•
V
BUS
Valid and session-end voltage thresholds. They are used to drive the session request
protocol (SRP), detect valid startup and end-of-session conditions, and constantly
monitor the V
•
V
BUS
the SRP (weak drive).
Caution: To guarantee a correct operation for the USB OTG HS peripheral, the AHB frequency
should be higher than 30 MHz.
30.4

OTG dual-role device

30.4.1

ID line detection

The host or peripheral (the default) role depends on the level of the ID input line. It is
determined when the USB cable is plugged in and depends on which side of the USB cable
is connected to the micro-AB receptacle:
•
If the B-side of the USB cable is connected with a floating ID wire, the integrated pull-
up resistor detects a high ID level and the default peripheral role is confirmed. In this
configuration the OTG_HS conforms to the FSM standard described in
section 6.8.2. On-The-Go B-device of the USB On-The-Go Supplement, Revision 1.3.
•
If the A-side of the USB cable is connected with a grounded ID, the OTG_HS issues an
ID line status change interrupt (CIDSCHG bit in the OTG_HS_GINTSTS register) for
host software initialization, and automatically switches to host role. In this configuration
the OTG_HS conforms to the FSM standard described by section 6.8.1: On-The-Go A-
Device of the USB On-The-Go Supplement, Revision 1.3.
30.4.2

HNP dual role device

The HNP capable bit in the Global USB configuration register (HNPCAP bit in the
OTG_HS_ GUSBCFG register) configures the OTG_HS core to dynamically change from
A-host to A-device role and vice-versa, or from B-device to B-host role and vice-versa,
according to the host negotiation protocol (HNP). The current device status is defined by the
1102/1381
sensing comparators with hysteresis used to detect VBUS_VALID, A-B Session
supply during USB operations.
BUS
pulsing method circuit used to charge/discharge V
RM0033 Rev 9
is sensed to be at
BUS
through resistors during
BUS
RM0033