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• Errata for "USB Revision 2.0 April 27, 2000" as of 12/7/2000
• Errata for "USB Revision 2.0 April 27, 2000" as of 12/7/2000
• Pull-up / Pull-down Resistors (USB Engineering Change Notice)
• Suspend Current Limit Changes (USB Engineering Change Notice)
• Device Capacitance (USB Engineering Change Notice)
• USB 2.0 Connect Timing Update (USB Engineering Change Notice as of April 4,
2013)
• USB 2.0 VBUS Max Limit (USB Engineering Change Notice)
• On-The-Go and Embedded Host Supplement to the USB Revision 2.0 Specification,
Revision 2.0 version 1.1a, July 27, 2012
• Maximum VBUS Voltage (USB OTGEH Engineering Change Notice)
• Universal Serial Bus Micro-USB Cables and Connectors Specification, Revision
1.01, 2007
33.2.2 USB
The USB is a cable bus that supports data exchange between a host computer and a wide
range of simultaneously accessible peripherals. The attached peripherals share USB
bandwidth through a host-scheduled, token-based protocol. The bus allows peripherals to
be attached, configured, used, and detached while the host and other peripherals are in
operation.
USB software provides a uniform view of the system for all application software, hiding
implementation details that make application software more portable. It manages the
dynamic attach and detach of peripherals.
There is only one host in any USB system. The USB interface to the host computer
system is referred to as the Host Controller.
There may be multiple USB devices in any system such as human interface devices,
speakers, printers, etc. USB devices present a standard USB interface in terms of
comprehension, response, and standard capability.
The host initiates transactions to specific peripherals, whereas the device responds to
control transactions. The device sends and receives data to and from the host using a
standard USB data format. USB 2.0 full-speed /low-speed peripherals operate at 12Mbit/s
or 1.5 Mbit/s.
Freescale Semiconductor, Inc.
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Chapter 33 Universal Serial Bus (USB) FS Subsystem
531
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