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DNT90 Integration Guide - 05/10/12
When a router/remote has data to send to its parent, it picks an open slot at random and transmits. It then
looks for its MAC address in the next beacon. If its MAC address is present in the beacon, it is temporarily
registered to the slot and continues to use it until all current data is sent, or its MAC address drops off the
beacon.
2.6.1 Fast Linking Techniques
Minimizing linking time is important in certain applications. For example, when the remotes in a system
are battery powered and wake from sleep occasionally to report data. Minimizing linking time increases
the operating battery life of the remotes. The basic techniques to reduce linking time include:
- use no more hop duration (dwell time) than necessary
- use no more slots than necessary for the application
- use no larger base slot size (BSS) than necessary
- transmit only dynamic cycle parameters once system nodes have static parameters
Once a complete set of cycled parameters has been receive by all routers and remotes in a system and
stored in memory, it is not necessary to send all of them again during a re-linking, as long as the system
configuration remains stable.
As discussed in Section 7.4.1, the base station in a DNT90 system can be configured to transmit “fast
beacons” for a period of time when powered up, reset or triggered with the
FastBeaconTrig
parameter.
Fast beacons are sent using a very short hop dwell time, facilitating fast system linking.
2.7 Transparent and Protocol-formatted Serial Data
A DNT90 remote can directly input and output data bytes and data strings on its serial port. This is re-
ferred to as
transparent
serial port operation. In a point-to-point system, the base can also be configured
for transparent serial port operation.
In all other cases, serial data must be
protocol
formatted:
- configuration commands and replies
- I/O event messages
- announcement messages including heartbeats
Protocol-formatted messages are discussed in detail in Section 7. Briefly, protocol-formatted messages
include a start-of-messages character, message length and message type information, the destination
address of the message, and the message payload.
Transparent data is routed using a
remote transparent destination address
. In a remote, this address de-
faults to the base, 0x000000, and in the base this address defaults to broadcast, 0xFFFFFF. These de-
faults can be overridden with specific radio addresses. For example, it is possible to set up transparent
peer-to-peer routing between two remotes in a point-to-multipoint or store-and-forward system by loading
specific MAC addresses in each radio’s remote transparent destination address.