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PakBus Networking Guide

filter which must describe all potential neighbors, but beacon traffic can be

reduced or eliminated so long as neighbor communications are usually

successful.

The P193 instruction does not initiate communications so it cannot be relied

upon to discover neighbors. The P190, P191, P192, P196, P198 and P224

instructions do initiate communications, so if a node is not already a neighbor

by another means they will use the static route specified in the Pxxx instruction

parameter (port and address) to try to establish that node as a neighbor.

As the basic mechanism of discovery in a PakBus network, whenever a device’s

neighbor list changes, whether the neighbor is lost or gained, it sends its new

neighbor list to all network routers (after a random delay of 1 to 32 seconds).

Whether a PakBus device loses or gains a neighbor it will send around its

neighbor list. If a neighbor router fails to respond to a Send Neighbor List

packet (even if the neighbor router happens to be LoggerNet) it will be

removed from the device’s neighbor list after 4 attempts.

When a device sends a hello message, either in response to a beacon or because

of a neighbor filter, it also sends its communications verification interval to

allow its possible future removal as a neighbor.

7.4.1 Beacon

For RF400 networks of more than a few nodes, beacons should

be avoided as the rf collisions and resultant retries can increase

network response times to unacceptable values.

Beaconing is a simple way for a device to discover its neighbors. When one

device hears another device beaconing, if the beaconing device is not yet a

neighbor it will answer the beacon with a hello message back to the beaconing

device. The beaconing device will answer with a hello response. The ‘hello

exchange’ will establish the two nodes as neighbors. The CR205 response to a

beacon is somewhat different (see 7.7.2).

Most PakBus devices are capable of beaconing (except the CR205). When

configured for beaconing a device sends out a broadcast beacon packet at

regular intervals. For LoggerNet the default beaconing interval is 60 seconds. A

setting of zero disables beacons. The beacon interval ranges are: 0 to 9999

seconds for a datalogger; 0 to 999 seconds for the LoggerNet Server; and 0 to

65535 seconds for the NL100.

An example broadcast beacon in LoggerNet’s Low Level Log:

09:24:38.558 T bd bd bd bd bd bd bd 8f ff

8f fe 0f ff 0f fe e6 60 bd

“8f ff” is the indicator of a broadcast beacon. The two bytes following the “8f

ff” contain the beaconing device’s PakBus Address in hexadecimal form. In

this example “8f fe” indicates that the LoggerNet server (4094 = ffeh) is the

beaconing device. The “bd”s are sent for baud rate detection if not connected

(datalogger offline).

NOTE

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