www.RFM.com
Technical s1.678.684.2000
Page 10 of 83
© 2011 by RF Monolithics, Inc.
E-mail:
DNT24 Integration Guide - 10/19/11
Figure 2.3.1
2.4 RF Channel Access
The time a DNT24 network stays on each frequency in its hopping pattern is called the hop
duration
or
dwell
time, which can be configured from 8 to 100 ms. Radio communication during each dwell is organ-
ized as a time division multiple access (TDMA)
frame
. A DNT24 frame begins with a base-mode
beacon
,
followed by 1 to 8 time
slots
used by the network children to transmit to their parent, as shown in Figure
2.4.1. A base-mode beacon can include up to 8 messages addressed to one or more child radios. The
number of slots is chosen accommodate the number of children that need to send messages each hop.
S y s t e m / N e t w o r k
C o n t r o l
M e s s a g e s t o
N e t w o r k C h i l d r e n
B a s e - M o d e
B e a c o n
E x a m p l e D N T 2 4 C o m m u n i c a t i o n F r a m e
A s s i g n e d
S l o t
O p e n
S l o t
O p e n
S l o t
M e s s a g e s
f r o m C h i l d
Figure 2.4.1
Each beacon includes the status of all slots - either
registered
(assigned) or
open
. When a child radio has
information to transmit to its parent, it randomly selects one of the open slots and transmits all or the first
part of its data. If the parent successfully receives the transmission, it includes the child’s
MAC
address in