Apc UPS control system Instrukcja Użytkownika Pobierz pdf (Strona 213)

interface serves a distinct "function", which is typically bound

to a different USB device driver. One common example is a USB

speaker with an audio interface for playback, and a HID interface

for use with software volume control.

Interface descriptor info (can be multiple per Config):

I: If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss

| | | |__NumberOfEndpoints

| | |__AlternateSettingNumber

| |__InterfaceNumber

|__Interface info tag

A given interface may have one or more "alternate" settings.

For example, default settings may not use more than a small

amount of periodic bandwidth. To use significant fractions

of bus bandwidth, drivers must select a non-default altsetting.

Only one setting for an interface may be active at a time, and

only one driver may bind to an interface at a time. Most devices

have only one alternate setting per interface.

Endpoint descriptor info (can be multiple per Interface):

E: Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=dddms

| | | |__EndpointMaxPacketSize

| | |__Attributes(EndpointType)

| |__EndpointAddress(I=In,O=Out)

|__Endpoint info tag

The interval is nonzero for all periodic (interrupt or isochronous)

endpoints. For high speed endpoints the transfer interval may be

measured in microseconds rather than milliseconds.

For high speed periodic endpoints, the "MaxPacketSize" reflects

the per-microframe data transfer size. For "high bandwidth"

endpoints, that can reflect two or three packets (for up to

3KBytes every 125 usec) per endpoint.

With the Linux-USB stack, periodic bandwidth reservations use the

transfer intervals and sizes provided by URBs, which can be less

than those found in endpoint descriptor.

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Apc UPS control system Instrukcja Użytkownika Strona 213