Campbell CR800 Specifications download pdf (Page 295)

Section 14. PakBus Networking

14-11

FIGURE 14.2-1B. Tree Map

In RF4xx networks, with all the remotes in range of LoggerNet’s RF4xx, you

can use the ‘flat’ configuration of Figure 14.2-1A. In RF4xx networks where

communications requires routers, use the ‘tree’ configuration of Figure

14.2-1B. Here, CR800 is probably neighbor-filter configured as a router to

CR800_2, and CR800_2 is probably neighbor-filter configured as a router

between CR800 and CR800_3.

Referring to Figure 14.2-1B, the shape of the map serves to disallow a direct

LoggerNet connection to CR800_2 and CR800_3, and implies constrained

routes that will probably be established by user-installed neighbor filters in the

routers. This assumes that LoggerNet beacons are turned off (with default

PBA of 4094, LoggerNet’s beacons would penetrate the neighbor filter of any

in-range or marginally in-range node).

14.3 PakBus Concepts

14.3.1 Packets

Mixed-array dataloggers transfer messages over a fixed end-to-end connection

that monopolizes path communication resources until a task is finished.

PakBus dataloggers, on the other hand, transfer messages in packets enabling

the real-time sharing of network communication resources by interleaving the

transfer of packets from multiple stations over the same hardware links.

There are two levels of PakBus packets. BMP5 packets handle high-level

datalogger functions such as clock check, program send, data collect and

logger-to-logger transfers. Low-level PakCtrl packets handle such functions as

the discovery of neighbors and router-to-router communications.

Packets are typically limited to 1000 bytes. Larger amounts of data are sent in

multiple packets. Each packet has a header containing source address,

destination address, neighbor information, and control information as well as

data. Once a packet is put onto the network, the established system of routers

will guide it to its destination. Packets can be stored in a router for a few

milliseconds to accommodate other packets needing the same link.

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Campbell CR800 Specifications Page 295