17 January, 2003
USB
6-103
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6.15 USB
6.15.1 SPECIFICATIONS
Data rates: 480 Mbps (high speed), 12 Mbps (full speed), 1.5 Mbps (low speed);
High-speed mode is only supported by USB 2.0.
6.15.2 USB 1.1/2.0
USB (Universal Serial Bus) offers simple connectivity for computers, printers,
keyboards, and other peripherals. In a USB environment, terminators, device IDs
(like SCSI), and DIP switch settings are not necessary.
USB 1.1 contains the following features:
•
Plug & Play
•
Hot swapping (cables can be connected and disconnected while the
computer and other devices are switched on)
•
No terminator or device ID required
•
Data rates of 12 Mbps (full speed), and 1.5 Mbps (low speed)
•
Common connectors for different devices
USB 2.0 is a successor to the USB 1.1 specification. It uses the same cables,
connectors, and software interfaces. It provides an easy-to-use connection to a
wide range of products with a maximum data rate of 480 Mbps (high speed).
Up to 127 devices can be connected and six cascade connections are allowed.
Power is supplied from the computer, and the maximum cable length is 5 m.
6.15.3 USB CONNECTORS
USB is a serial protocol and a physical link transmitting all data on a single pair of
wires. Another pair provides power to downstream peripherals.
The USB standard specifies two types of connectors, type “A” connectors for
upstream connection to the host system, and type “B” connectors for downstream
connection to the USB device.
Type “A” connector
Type “B” connector
G080D983.WMF
G080D982.WMF