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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 401
UG585 (v1.11) September 27, 2016
Chapter 15: USB Host, Device, and OTG Controller
15.2 Functional Description
This section generally applies to both device and host modes.
15.2.1 Controller Flow Diagram
The controller flow diagram in Figure 15-6 shows the USB data transfer flows, the descriptor flows,
and the interface to software.
15.2.2 DMA Engine
Data Transfers
In host mode, the data structures are defined by the EHCI specification and represent queues of
periodic and asynchronous transfers to be performed by the host controller including the split
transaction requests that allow the controller to direct packets to FS/LS devices that are downstream
of an external HS hub or root hub. Host mode uses the queue head (QH), queue element transfer
descriptor (qTD), isochronous transfer descriptor (iTD), split transaction isochronous transfer
descriptor (siTD) and the periodic frame span transversal node (FSTN) data structures.
In device mode, the data structures are simpler and consist of device queue heads (dQH) and device
transfer descriptors (dTD) that are used in a linked-list fashion.
X-Ref Target - Figure 15-6
Figure 15-6: USB Controller Flow Diagram
* Bus Interface
* Data Movement
* Host: Periodic and Async Schedules
* Device: Endpoint Queue Head
System
Memory
AHB Master
Control and Status
Registers
DMA Engine
Tx and Rx FIFO
channels
Dual-port
RAM
* Interval Timers
* Error Handling
* CRC Handling
* Bus Handshake Generation
Protocol Engine
* Port Status and Control
* Transceiver Interface Logic
Port Controller
ULPI
Interface
Interrupts
Microprocessor(s)
APB Slave
ULPI Master
Context (QH and TD
data structures)
IRQ to GIC
DMA DMA
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