July 2013 10.5 The USB Interface of the iTNC 1895
USB hub The power supply for the USB hub must comply with EN 50 178, 5.88
requirements for "low voltage electrical separation."
For more information on the USB interface, see the iTNC 530 Technical
Manual.
Setup The USB interface connects the USB peripheral devices with the USB host.
The topology of a USB connection may consist of several levels arranged in a
star configuration. Every level consists of a USB hub to which other USB
devices or hubs are connected in a star configuration. A maximum of 127 USB
devices can be connected to a USB host in this way.
Topology of the USB interface:
Functionality and
signal designations
USB uses packet-based communication over two differential data lines. This
reduces radiation and increases transmission reliability. USB provides
significantly higher data transfer rates than the parallel / Centronics, and serial
/ RS-232, RS-422 external interfaces:
USB full speed of up to 12 Mbps
USB low speed of up to 1.5 Mbps
Conventional interfaces, such as the RS-232, are more suitable for time-critical
applications because they are not based on packets which reduce the transfer
rate (in case of packets with only a few bytes) or delay transmission (when
collecting bytes for filling a packet).
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