SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The USB controller provides full OTG negotiation by supporting both the Session Request Protocol (SRP) and the Host Negotiation Protocol (HNP). The session request protocol allows devices on the B side of a cable to request the A side device turn on VBUS. The host negotiation protocol is used after the initial session request protocol has powered the bus and provides a method to determine which end of the cable will act as the host controller. When the device is connected to non-OTG peripherals or devices, the controller can detect which cable end was used and provides a register to indicate if the controller should act as the host or the device controller. This indication and the mode of operation are handled automatically by the USB controller. This auto-detection allows the system to use a single A/B connector instead of having both A and B connectors in the system and supports full OTG negotiations with other OTG devices.
In addition, the USB controller provides support for connecting to non-OTG peripherals or host controllers. The USB controller can be configured to act as either a dedicated host or device, in which case, the USB0VBUS and USB0ID signals can be used as GPIOs or any corresponding alternate functions. However, when the USB controller is acting as a self-powered device, a GPIO input or analog comparator input must be connected to VBUS and configured to generate an interrupt when the VBUS level drops. This interrupt is used to disable the pullup resistor on the USB0DP signal.
NOTE
When the USB module is in operation, MOSC must be the clock source, either with or without using the PLL, and the system clock must be at least 30 MHz.