Colortrac SmartLF Ci 40, Service Manual

Page: 13 / 101

Page 13
Ci Scanner Service Manual
9. SCANNER ACCESSORIES
9.1. USB CABLE TYPE A AND B
Length: 2 meter max.
Speed: 480Mb/s
This high quality USB cable complies fully with
the USB 2.0 specification.
The USB transfers signal and power over a
four-wire cable. The signalling occurs over two
wires on each point-to-point segment.
There are three data rates:

The USB high-speed signalling bit rate is
480 Mb/s.

The USB full-speed signalling bit rate is 12
Mb/s.
A limited capability low-speed signalling mode
is also defined at 1.5 Mb/s.
USB 2.0 host controllers and hubs provide capabilities so that full-speed and low-speed data can
be transmitted at high-speed between the host controller and the hub, but transmitted between
the hub and the device at full-speed or low-speed. This capability minimises the impact that full-
speed and low-speed devices have upon the bandwidth available for high-speed devices.
The low-speed mode is defined to support a limited number of low-bandwidth devices, such as
mice, because more general use would degrade bus utilisation. The clock is transmitted, encoded
along with the differential data. The clock encoding scheme is NRZI with bit stuffing to ensure
adequate transitions. A SYNC field precedes each packet to allow the receiver(s) to synchronise
their bit recovery clocks.
The cable also carries VBUS and GND wires on each segment to deliver power to devices. VBUS
is nominally +5 V at the source. The USB allows cable segments of variable lengths, up to
several meters, by choosing the appropriate conductor gauge to match the specified IR drop and
other attributes such as device power budget and cable flexibility. In order to provide guaranteed
input voltage levels and proper termination impedance, biased terminations are used at each end
of the cable. The termination’s also permits the detection of attach and detach at each port and
differentiate between high/full-speed and low-speed devices.
All devices have an upstream connection. Upstream and downstream connectors are not
mechanically interchangeable, thus eliminating illegal loopback connections at hubs. The cable
has four conductors: a twisted signal pair of standard gauge and a power pair in a range of
permitted gauges. The connector is four-position, with shielded housing, specified robustness,
and ease of attach-detach characteristics.
NOTE:
Colortrac provides a 2m USB 2.0 cable as part of
the accessories package. 2m is the MAXIMUM
length we recommend. Any cables longer than the
recommended
2m is at the customers’ discretion,
and Colortrac can not be help accountable for any
failures during operation because of this.