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2: USB architecture
Note: It is assumed that you
have a good understanding of
USB principles and architecture.
For detailed information, refer to
Universal Serial Bus Class
Definitions for Communication
Devices, Version 1.1. This (and
other resources) can be
downloaded from www.usb.org.
Rev 1.9 Sep.08
This chapter describes supported driver architectures for data
transfer, and the physical USB interface for each architecture.
USB standards compliance
The AC59X, AC8XX, C59X, C8XX, MC572X, and MC87XX
comply with USB 2.0 standards, including the following:
USB slave only
•
•
USB 2.0 (backwards compatible with USB 1.1)
•
Full‐speed 12 Mb/s and low‐speed 1.5 Mb/s data transfer
rates.
•
High‐speed 480 Mb/s is supported by C8XX, MC8785V,
MC8790, MC8790V, MC8791V, and MC8792V.
Standard USB flow control
•
Standard USB power management—Suspends the USB bus
•
when it is idle, to conserve power.
The architecture for these devices is derived from the Abstract
Control Model (ACM) described in the Universal Serial Bus
Class Definitions for Communication Devices, Version 1.1 (CDC)
specification.
To best support advanced power management, a modified
(non‐composite) endpoint / interface model combines the
Communication and Data Interface pipes with two proprietary
pipes (HIP and NMEA/Data1) into one vendor‐specific
interface.
Note: These devices do not claim any CDC classes in the descriptors
and do not support functional descriptors. As a result, these devices
are not normally compatible with native CDC-ACM drivers.
Supported driver architectures
The modules support two or three driver architectures:
Non‐multiplexing (Non‐MUX) mode ‐ Supported service
•
channels (see
sets of endpoints.
Multiplexing (MUX) mode ‐ All service channels are carried
•
over a single set of endpoints, and if supported, Mass
Storage is implemented over a second set of endpoints.
Hybrid‐MUX mode ‐ Data / AT services are carried over
•
one pair of endpoints; the other services are multiplexed
Proprietary and Confidential
Services
, page 33) are carried over multiple
2
13
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