USB 2.0 Controller

Versal ACAP Technical Reference Manual (AM011)

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1.4 English

The controller is compliant with the USB 2.0 specification to support high, full, and low-speed modes in all configurations. It can be configured as a host, a device, or in on-the-go (OTG).

In host mode, the controller is compatible with the Intel extensible host controller interface (xHCI) specification. In device mode, it supports up to 12 endpoints (6 in and 6 out). The controller's I/O uses an 8-bit universal low peripheral interface (ULPI) to connect the VersalĀ® device to an external PHY via the PMC MIO pins. The controller operates at 20 MHz using the USB_REF_CLK from the LPD clock controller. The ULPI interface is clocked at 60 MHz by the PHY. The controller provides transfer rates up to 480 Mb/s for high-speed mode. The 32-bit AXI slave programming interface is accessed by system software to control the modes. The programming interface provides access to the USB_2_REGS controller and USB_2_XHCI core register sets. The AXI slave is attached to the LPD IOP slave switch.

The 64-bit AXI master interface is used by the DMA unit to read descriptor tables and access data buffers. The AXI master is attached to the LPD IOP master switch. The controller includes a single dual-port RAM to store RX FIFO data, TX FIFO data, and to cache descriptors. The AXI master port and the protocol layers access the RAMs using the buffer management unit. The RAM provides buffering of transaction data between the ULPI interface and system memory. The host controller is a schedule driven environment for data transfers of periodic (interrupt and isochronous) and asynchronous (control and bulk) types.

Device mode includes a simple pair of descriptors to respond to USB data transfers in a timely manner between the software and the USB. The transfer descriptors of the host schedules and device endpoints control the DMA engine to move data between the 64-bit AXI master system bus interface and the RX and TX data FIFOs in RAM that respond in real time to the USB. The controller makes strategic use of software for tasks that do not require time-critical responses. This reduces the amount of hardware logic. At the same time, the controller includes hardware assistance logic to enable the controller to respond quickly to USB events and simplify the software.

The controller includes the hibernation and low-power modes.