YORK INTERNATIONAL
11
FORM 450.20-N20 (702)
2
NETWORK TOPOLOGY
Background vs. Foreground
Communications
The ISN network uses both “Background” and
“Foreground” communication to ensure essential data
is transmitted without delay.
Background communication supports multiple source
messages at the same time, although the speed of
communication may be affected if large quantities of
data are transmitted around the network.
Examples of background communication are:
• Automatic transfer of digital states and analog
values between ISN controllers.
• Analog and Digital alarms to a Universal
LINC232 connected to a PC running the York
Facility Manager for Windows™ software.
• Using a PC running the York Facility Manager
for Windows™ software to read and write data
to and from an ISN controller via a Universal
LINC232.
• Analog and Digital alarms to a LINC Guardian.
Only one foreground communication to a specific
ISN controller can occur at any one time. A “busy”
message is displayed if the ISN controller is already
communicating with another device using this
method. Background communication can occur
simultaneously with foreground communication.
Examples of foreground communications are:
• Manual communications between ISN control-
lers using the optional keypad/display or Win-
dows™ HyperTerminal software running on a
PC connected to the RS232 port of an ISN
controller.
• Using a PC running the YORK Facility Manager
for Windows™ software to write data into an
ISN controller via a Universal LINC232.
• Printing of Analog and Digital alarms to a
Universal LINC232 connected to an RS232
printer.
• Using a PC running the YORK IcE to Save or
Load an ISN controller Configuration via a
Universal LINC232.
• Using a PC running the YORK Facility Manager
for Windows™ to Save or Load an ISN control-
ler Configuration via a Universal LINC232.
Speed of Communications
The ISN network communicates at either a 19.2 or 50
kbaud rate. The Universal LINC232 is switch se-
lected to communicate at 4800, 9600, or 19,200
(19k2) baud rates through the serial RS232 port.
The typical response time between ISN controllers
for automatic transfer of data or alarms is
100 milliseconds.
Each Universal LINC485 Repeater and Router
increases the typical response time by
100 milliseconds.
Summary of ISN Network Restrictions
• The maximum single length of a network or
subnetwork is 4000 ft (1200 m). This can be
extended to 12,000 ft (3600 m) using two
Universal LINC485 devices configured as
repeaters. This provides a maximum combined
network end-to-end length of 36,000 ft. (10,800
m).
• A Universal LINC485 configured as a repeater is
required every 4000 ft. (1200 m) or 32 nodes. A
node is any device which uses an RS485 driver,
such as an ISN controller, Universal LINC485 or
Universal LINC232.
• The maximum number of nodes on a main
network is 92 plus two Universal LINC485
devices configured as repeaters. A maximum of
91 plus two Universal LINC485 devices are
allowed on a subnetwork.
• When the main network or subnetworks are
extended between different buildings, the
ground/earth voltage of the buildings must be at
