Echelon ISI - Manual (Page 16)

ISI Programmer’s Guide 14
Limit Value Notes
Maximum number of selectors
per assembly 63
Recommended maximum
number of selectors per
assembly
4
ISI and Energy Storage Devices
In simple devices, such as a light or a switch, a common implementation uses an
energy storage power supply, as described in the
PL 3120, PL 3150 and PL 3170
Power Line Smart Transceiver Data Book . A device using this type of power
supply can be referred to as an energy storage device . In these devices, under
certain worst-case circumstances, the maximum packet size that can be sent is
limited. ISI implements two versions of DRUM, CSMO, CSMA, and CSMR
messages (See ISI Messages in this chapter and the ISI Protocol Specification ).
The normal version is short enough to be sent by an energy storage device, and is
restricted to usage with standard network variable types and standard functional
profiles only. Since energy storage devices can receive any length message, they
can only host connections that use SNVTs and SFPTs, but can join a connection
that uses UNVTs and UFPTs. Compound assemblies that are based on a single
functional profile and hosted on an energy storage device also need to start with
member 1.
The extended versions of these messages contain additional functionality, but
result with the message potentially being too long to be transmitted by an energy
storage device. The extended message types do not have the limitations
summarized above.
By default, the ISI engine recognizes all supported message types, but will only
issue the shorter versions of the DRUM, CSMO, CSMA, and CSMR messages. To
enable the use of the extended DRUMEX, CSMOEX, CSMAEX, and CSMREX
messages, specify
isiFlagExtended when starting the ISI engine.
All ISI devices may use the standard message formats if the functionality
provided by the extended formats is not required, but energy storage devices may
not use the extended formats. Energy storage devices may be capable of
successful transmission of the extended messages under certain conditions.
However, this should not be relied upon, since these conditions include the
momentary line condition and part tolerance details that cannot be relied upon
for mass production.
ISI domain address servers for power line channels cannot be built with energy-
storage power supplies. These devices would fail to transmit DIDRM and DIDCF
messages under worst-case conditions (line voltage, line impedance, and part
tolerances).