Bioscrypt Inc. VSTICLASS Manual De Usuario

Document #430-90003-08

© Copyright 2003, Bioscrypt Inc.  All rights reserved.

RS-485 is a networking specification similar to Ethernet, which is used for computer

networks.  RS-485 is different from Ethernet and is not compatible with modern

computer networks.  This means that you cannot connect most Veri-Series units

directly up to Ethernet networks.  The V-Station does however support Ethernet.
RS-485 has two distinct advantages over the more common RS-232.  First, it allows

you to connect up to 31 Veri-Series units to a PC (the PC will either need internal

support for RS-485 or will require an external RS-232/RS-485 converter available

from Bioscrypt).  Second, the RS-485 specification allows for cable run lengths up

to 4000 feet (1200 meters) at modest baud rates.
An RS-485 network will need to be implemented in the following circumstances:

o

 

There are multiple readers that must be connected together so that

templates can be distributed among the units

o

 

There is only a single reader, but it is over 100 feet (30 meters) from the host

PC.

Ethernet is a networking specification now used all over the world for computers,

IP phones, and other devices.  The only Bioscrypt product which currently supports

this standard is the V-Station.  Ethernet has many advantages over an RS-485

network, namely, faster data transfer rates over greater distances.  However, the

prime advantage to your network of Bioscrypt readers will be the ability to

connect many more units, enjoy easier configuration from the PC, and avoid

conflicts when multiple units transmit at the same time (i.e., if two or more units

have the same unit ID).  Care must be taken to ensure the security of V-Stations

placed on a network which is also shared by PCs other than the administration

machine or other peripherals.

The Veri-Series readers provide a 2-wire, half-duplex RS-485 interface.  The main

run cable should be low capacitance, twisted pair cable, with approximately 120-

ohm characteristic impedance.  Category 5 rated communications cable is used

in Ethernet networks.  This cable is typically 24 AWG (solid), unshielded, twisted-pair

with a shunt capacitance of approximately 17 pF/ft and characteristic

impedance of 100 – 120 ohms.  This is the recommended cabling for RS-485

communications.  In certain electrically noisy environments, a shielded cable may

be required.