NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
110 / 205
aaa-028034
D Q
R
D Q
R
D Q
R
D Q
R
D Q
R
D Q
R
D Q
S
S0 S1 S2 S3 S4 S5 S6
CLK
RFMRST
7-bit random number
Galois primitive polynomial = X7 + X3 + 1
Figure 33. LFSR implementation
A value of all zeros in the LFSR will remain unchanged with every clock input and cannot
be used as a starting "seed."
The resulting range of times for the initial and interframe pseudo-random time will be
as given in Table 100 for both the design center and the variation resulting from the
tolerance of the MFO clock.
Table 100. Randomization interval times
Time Interval Including
MFO Tolerance (ms)
Time
Interval
Random
ization
Number
Ideal Time
Interval (ms)
Minimum Maximum
1 40 37.2 42.8Initial
127 5080 4347.2 5434.6
1 1 0.93 1.07Interframe
127 127 118.1 135.9
10.16.3.5 Frame number time
The frame number time, t
FN
, is only used between frames and is based on a selectable
time from 0 to 63 ms and the number of the frame that was just transmitted as given in
Table 101. If the frame number time is not used, the value of the selected time should be
set to zero. The maximum number of frames is defined by the FNUM[3:0] control bits.
The range of the frame number time is a multiple of 0 to 63 ms using a clock generated
from the MFO divided by 125. The value of this time multiple can be changed by the
RFFT[5:0] bits in the RFCR6 register. The BPS[7:0] control bits are set to $34 by the
RFMRST signal which results in a default data rate of 9434 bits/sec.
To Next Page
Loading...