AT32AP7002_1 Datasheet, PDF (601/896 Pages) ATMEL Corporation – AVR32 32-bit Microcontroller

AT32AP7002
31.6 USB V2.0 High Speed Device Introduction
31.6.1
The USB V2.0 High Speed Device provides communication services to/from host when
attached. 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.
USB V2.0 High Speed Transfer Types
A communication flow is carried over one of four transfer types defined by the USB device.
A device provides several logical communication pipes with the host. To each logical pipe is
associated an endpoint. Transfer through a pipe belongs to one of the four transfer types:
• Control Transfers: Used to configure a device at attach time and can be used for other device-
specific purposes, including control of other pipes on the device.
• Bulk Data Transfers: Generated or consumed in relatively large burst quantities and have wide
dynamic latitude in transmission constraints.
• Interrupt Data Transfers: Used for timely but reliable delivery of data, for example, characters or
coordinates with human-perceptible echo or feedback response characteristics.
• Isochronous Data Transfers: Occupy a prenegotiated amount of USB bandwidth with a
prenegotiated delivery latency. (Also called streaming real time transfers.)
As indicated below, transfers are sequential events carried out on the USB bus.
Endpoints must be configured according to the transfer type they handle.
Table 31-3. USB Communication Flow
Transfer
Direction
Bandwidth
Control
Bidirectional Not guaranteed
Isochronous Unidirectional Guaranteed
Interrupt
Unidirectional Not guaranteed
Bulk
Unidirectional Not guaranteed
Endpoint Size
8,16,32,64
8-1024
8-1024
8-512
Error Detection
Yes
Yes
Yes
Yes
Retrying
Automatic
No
Yes
Yes
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