Echelon ISI - Manual (Page 13)

11 ISI Programmer’s Guide
ISI does not support redundant routers, and the user is responsible for avoiding
looping topologies. The network topologies described in this section will not
cause looping topologies.
Connection Complexity
A single device can join multiple connections; limited by available address, alias,
and connection table space on the device. Devices can map one or more network
variables to a single selector, but it is the device's responsibility to ensure that at
most one input network variable is mapped to a single selector. The number of
network variables in any given connection and on any single device is only
limited by device resources (alias, address, and connection table space).
Connections can include an unlimited number of devices. Devices supporting
aliases (those not built with the IsiCompactManual or IsiCompactAuto library)
can extend connections; that is, a single network variable on a device can join
multiple connections at the same time. Devices using the IsiCompactManual or
IsiCompactAuto libraries cannot extend connections (no support for aliases) and
cannot replace or remove connections (no support for removal) other than by
returning the device to factory settings. A standard mechanism is supported
with each ISI device to return to factory defaults.
Identification of Connections
Connections are established using a process called enrollment . A device may
accept a connection invitation and join a connection on the basis of a single
network variable type alone. For example, a device can choose to join a
connection that uses a SNVT_switch network variable. A device may accept a
connection invitation and join a connection on the basis of a single functional
block. For example, a device can choose to join a connection that offers data from
a SFTPclosedLoopSensor functional block with the SNVT_xxx output
implemented as a SNVT_amp network variable. Standard connections are those
that can be understood (and accepted or refused) solely by knowledge derived
from the standard resource file set. Enrollment procedures that require
additional knowledge are collectively named manufacturer-specific connections ,
although such a connection may not be limited to a single manufacturer. For
example, a group of manufacturers may share knowledge required in the
understanding (accepting) of those connections. The complexity of manufacturer-
specific connections is unlimited (but cannot exceed 63 selectors, and should not
exceed 4 selectors). For example, a single manufacturer-specific open enrollment
message can contain a number of different standard and non-standard functional
profiles. The simple case of a manufacturer-specific connection allows enrollment
of user network variables and profiles.
Address Table Size
Neuron C applications should maximize the address table size using the
#num_addr_table_entries compiler directive. The maximum size for Neuron C is
15. Even though most ISI devices require fewer address table entries when self-
installed, implementing a 15-entry address table if space is available allows for
versatile and complex connections when used in a managed network.