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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 445
UG585 (v1.11) September 27, 2016
Chapter 15: USB Host, Device, and OTG Controller
Functional Block Diagram
On the left side of Figure 15-17 is a typical hub implementation with a companion transaction
translator controller. It shows two ongoing asynchronous transactions capable of ping-pong access
from each end. Periodic traffic is aggregated into a single data stream for each direction while a table
of state and context for each pipe is stored within the transaction translator.
The right side of Figure 15-17 shows how the same functions have been integrated into the host
controller. The advantage of integrating those functions into the host controller is that the changes
to the EHCI host controller driver (HCD) are minimal while allowing direct connection of FS and LS
devices without the need for a companion controller or external USB 2.0 hub. In addition, the host
controller with the transaction translator requires less local data storage than a hub-based
transaction translator because the data storage is provided by main memory instead of
hardware-based RAM. The host controller supports 16 periodic contexts and 2 asynchronous
contexts.
X-Ref Target - Figure 15-17
Figure 15-17: USB Host Embedded Transaction Translator Implementation
UG585_c15_11_030413
Traditional Hardware Based Companion
Controller In a Hub-based Design
Embedded Transaction Translator in Host Mode
Using EHCI Software Model
EHCI High Speed Controller
Port Controller
Latency FIFOs
Small
Latency FIFOs
High Speed
Protocol Engine
Full/Low Speed
Protocol Engine
High-speed Handler
Full/Low Speed Handler
HS USB 2.0
EHCI Shared
Memory
EHCI Software
Stack
FS/LS USB
FS/LS USB
Iso/Int
State &
Context
Iso/Int
State &
Context
B/C
State &
Context
B/C
Transfer
TT Traffic
Management
Iso/Int
Transfer
(16)
(2)
(16)
Iso/Int
Transfer
B/C
State &
Context
B/C
In/Out
FIFO
B/C
In/Out
FIFO
Iso/Int
Start-
split
FIFO
Iso/Int
Compl.
Split
FIFO