USB Controller Host and Peripheral Modes Operation | www.ti.com |
3.6Reset Considerations
The USB controller has two reset sources: hardware reset and the soft reset (RESET bit in CTRLR register).
3.6.1Software Reset Considerations
When the RESET bit in CTRLR is set, all the USB controller registers and DMA operations are reset. The bit is cleared automatically.
A software reset on the ARM or DSP CPUs does not affect the register values and operation of the USB controller.
3.6.2Hardware Reset Considerations
When a hardware reset is asserted, all the registers are set to their default values.
3.6.3USB Reset Considerations
When operating in peripheral mode, a USB reset received from the host causes some internal registers to be reset. The USB controller setup operations (for example FIFO sizing) in peripheral mode should be performed after receiving the USB reset, and again on each subsequent USB reset. There are some conditions where multiple USB reset interrupts may be received in rapid succession. Good interrupt handling practices must be observed to assure that the setup is performed (again) after the final USB reset interrupt.
Software must teardown any TX DMA channel use upon receipt of a USB reset. See Section 3.3.2.8.
3.7Interrupt Support
The USB peripheral presents a single interrupt to the ARM interrupt controller (AINTC). For information on the mapping of interrupts, refer to the
3.8EDMA Event Support
The USB is an internal bus master peripheral and therefore does not utilize any EDMA events. The registers support only individual access. Bursting data to or from the USB register space through EDMA is not supported.
3.9Power Management
The USB controller can be placed in reduced power modes to conserve power during periods of low activity. The power management of the peripheral is controlled by the processor Power and Sleep Controller (PSC). The PSC acts as a master controller for power management for all of the peripherals on the device. For detailed information on power management procedures using the PSC, see the TMS320DMxxx DMSoC ARM Subsystem Reference Guide (spru856).
74 | Universal Serial Bus (USB) Controller |
