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DNT24 Integration Guide - 10/19/11
changes. When a router or remote has collected a full set of cycled parameters, it can issue an optional
initial heartbeat message and then optional periodic heartbeat messages which allow an application to
maintain the status of all routers and remotes in its DNT24 system.
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
- use no more hops in the hopping pattern than are necessary
- transmit only dynamic cycle parameters once system nodes have static parameters
In the United States and Canada, the DNT24 complies with DTS (DSSS) regulations based on the band-
width of its transmitted spectrum. In this case, frequency hopping is optional and when frequency hopping
is used there is no minimum requirement on the number of hopping channels that can be used. As dis-
cussed in Section 7.4.2., there are two 5-channel hopping patterns that can be used to help minimize link-
ing time. All DNT24’s in a system must be preset to one of these 5-channel hopping patterns in order to
achieve fast linking. Note that the 5-channel hopping patterns cannot be used in Europe.
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 DNT24 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 DNT24 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 or in multi-point systems when
broadcast addressing is used, the base can also be configured for transparent serial port operation.
In all other cases, serial data will 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.
