NXP Semiconductors FXTH870 D Series, Руководство пользователя

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FXTH870xD
Sensors
114 Freescale Semiconductor, Inc.
13.3 Transmission Randomization
When there are two or more different transmitters, the clock rates of each may drift into synchronism with each other; and there
is the possibility of RF data collisions and the loss of data from both transmitters. In order to reduce possible RF data collisions
each transmission will contain from 1 to 16 frames of data. Each frame may be spaced at after the initially timed transmission
start time and between any two data frames as shown in
Figure 91 .
Figure 91. Datagram Overview
The generation of the initial and interframe time intervals can be done with a combination of a programmable counter, a pseudo-
random interval generator and a frame counter as shown in
Figure 92 . The initial time interval can be done by adjusting the start
time using the MCU or using this interval timing generator.
Figure 92. Initial and Interframe Timing
SPACE
SPACE
t
0
Time Not To Scale
SPACE
Interframe Intervals
1 to 16 Data Frames
With Identical Data
Start of Time
Interval for
Datagram
DATA FRAME DATA FRAME DATA FRAME
Space Intervals have No Carrier Frequency Output, equivalent to Data = 0
t
DATA
Initial Interval
and may have the RFM crystal oscillator, VCO and PLL turned off by the IFPD bit.
t
0
Time Not To Scale
Interframe Interval 1
Start of Time
Interval for
Datagram
t
BASE
Initial Interval
40 x t
RAND
t
BASE
t
RAND
t
FN
t
BASE
t
RAND
t
FN
Interframe Interval 2
t
BASE,
t
RAND
and t
FN
may be all zero in the initial interval.
t
BASE,
t
RAND
and t
FN
may be all zero in an interframe interval.
All interframe intervals may have different t
BASE,
t
RAND
and t
FN
times.
Note: If t
BASE
and t
FN
are both set to non-zero, and t
RAND
is set to 0, the system
will decrement both t
BASE
and t
FN
simultaneously rather than serially, such that the
effective Interframe Interval will be equal to the larger of t
BASE
or t
FN
settings.