Datasheet

SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
830
37.5 Functional Description
37.5.1 USB V2.0 High Speed Device Port Introduction
The USB V2.0 High Speed Device Port 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 communication flows.
37.5.2 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 37-2. USB Communication Flow
Transfer Direction Bandwidth Endpoint Size Error Detection Retrying
Control Bidirectional Not guaranteed 8,16,32,64 Yes Automatic
Isochronous Unidirectional Guaranteed 8–1024 Yes No
Interrupt Unidirectional Not guaranteed 8–1024 Yes Yes
Bulk Unidirectional Not guaranteed 8–512 Yes Yes