Echelon ISI - Manual (Page 15)

13 ISI Programmer’s Guide
Earshot Problems
Open media such as power line may experience occasional communication
outages due to interference from other power line devices or neighboring
networks. In addition, an open media device may receive packets from devices
using the same media in neighboring networks. The ISI protocol handles
transient communication outages gracefully: when devices fail to recognize
network problems or changes to network address or connection information due
to transient outages, devices will recover once the outage has come to an end.
Occasional and unexpected receipt of network data from distant sites will cause
no harm, but if this possibility exists, a domain address server and ISI-DA can be
used to logically isolate the networks and prevent inadvertent connections
between devices in neighboring networks. Critical processes such as device and
domain ID acquisition are protected with a user-confirmed protocol, preventing
devices from being hijacked by other sites in earshot.
The following table shows a summary of key limits:
Limit Value Notes
Maximum device count ISI-S 32
Recommended maximum device
count ISI-S 26
Maximum device count ISI-DA 200
Recommended maximum device
count ISI-DA 160
See text on previous page.
Maximum number of network
variables per device 254
Maximum number of aliases per
device
254, optional
Devices may contain
larger numbers of NVs or
aliases, but those with an
index > 254 cannot be
used with an ISI network.
If an ISI device is moved
to a managed network, it
can reveal extra
functionality with
additional NVs and
aliases.
Maximum number of
connections per device
Limited by
device
resources, but
cannot exceed
254
The ISI libraries provide a
default implementation of
an ISI connection table
with 8 entries, but the
application may override
this with a larger or
smaller table.
Maximum number of connection
assemblies per device 254 This is determined by the
NV maximum, but cannot
exceed 254.