Bioscrypt Inc. VSTICLASS Manual De Usuario

Document #430-90003-08

© Copyright 2003, Bioscrypt Inc.  All rights reserved.

faster Ethernet varieties (such as gigabit) if PCs or other peripherals are to be

placed on the same network.
With most Ethernet networks, straight-thru cables should be used.  However, in the

event of a single reader-to-PC network, a cross-over cable must be used.  There

are other special considerations for such a network.  Please see the next section

on connecting to the computer.

Communication cables for RS-485 should be laid out in a daisy chain.  See figure

11. Long stubs (T connections) should be avoided because they create

discontinuities and degrade signal quality. If the stub is long, a signal that travels

down the stub reflects to the main line after hitting the input impedance of the

device at the end of the stub. This impedance is high compared with that of the

cable. The net effect is degradation of signal quality on the bus. Keeping the stubs

as short as possible avoids this problem. Instead of adding a long branch stub,

loop the main cable to the device you wish to connect.
DO NOT connect devices in a STAR configuration – this creates long stubs and is a

cause for concern.  This configuration usually does not provide a clean signaling

environment even if the cable runs are all of equal length.  The star configuration

also presents a termination problem, because terminating every endpoint would

overload the driver.  Terminating only two endpoints solves the loading problem

but creates transmission-line problems at the un-terminated ends.  A true cascade

or daisy chain connection avoids these problems.