AT91SAM9261_14 Datasheet, PDF (579/749 Pages) ATMEL Corporation – DSP Instruction Extensions

37.5 Functional Description
37.5.1
USB V2.0 Full-speed Introduction
The USB V2.0 full-speed provides communication services between host and attached USB
devices. Each device is offered with a collection of communication flows (pipes) associated with
each endpoint. Software on the host communicates with a USB device through a set of commu-
nication flows.
Figure 37-3. Example of USB V2.0 Full-speed Communication Control
USB Host V2.0
Software Client 1 Software Client 2
Data Flow: Control Transfer
Data Flow: Isochronous In Transfer
Data Flow: Isochronous Out Transfer
EP0
USB Device 2.0
EP1 _{Block 1}
EP2
Data Flow: Control Transfer
Data Flow: Bulk In Transfer
Data Flow: Bulk Out Transfer
EP0
USB Device 2.0
EP4 _{Block 2}
EP5
USB Device endpoint configuration requires that
in the first instance Control Transfer must be EP0.
The Control Transfer endpoint EP0 is always used when a USB device is first configured (USB v. 2.0 specifications).
37.5.1.1
USB V2.0 Full-speed Transfer Types
A communication flow is carried over one of four transfer types defined by the USB device.
Table 37-2.
Transfer
Control
Isochronous
Interrupt
Bulk
USB Communication Flow
Direction
Bandwidth
Bidirectional Not guaranteed
Unidirectional
Guaranteed
Unidirectional Not guaranteed
Unidirectional Not guaranteed
Supported Endpoint Size
8, 16, 32, 64
256
≤64
8, 16, 32, 64
Error Detection
Yes
Yes
Yes
Yes
Retrying
Automatic
No
Yes
Yes
37.5.1.2
USB Bus Transactions
Each transfer results in one or more transactions over the USB bus. There are three kinds of
transactions flowing across the bus in packets:
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