FXTH870xD
Sensors
116
Freescale Semiconductor, Inc.
Figure 93. 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 71
for both the design
center and the variation resulting from the tolerance of the MFO clock.
13.3.5
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 72
. 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.
Table 71. Randomization Interval Times
Time
Interval
Randomization
Number
Ideal Time Interval (ms)
Time Interval Including MFO Tolerance (ms)
Minimum
Maximum
Initial
1
40
37.2
42.8
127
5080
4347.2
5434.6
Interframe
1
1
0.93
1.07
127
127
118.1
135.9
Table 72. Frame Number Interval Times
Value of
FNUM[3:0]
Number of
Frames
Frame Interval Where
Time Added
Nominal Frame Number Time Interval Added (ms)
Minimum
Maximum
0
1
None
n/a
n/a
1
2
1 - 2
1
63
2
3
2 - 3
2
126
3
4
3 - 4
3
189
4
5
4 - 5
4
252
5
6
5 - 6
5
315
6
7
6 - 7
6
378
7
8
7 - 8
7
441
8
9
8 - 9
8
504
D Q
R
D Q
R
D Q
R
D Q
R
D Q
R
D Q
R
D Q
S
S
0
S
1
S
2
S
3
S
4
S
5
S
6
CLK
RFMRST
7-BIT Random Number
Galois Primitive Polynomial = X
7
+ X
3
+ 1
Summary of Contents for FXTH870 D Series
Page 86: ...FXTH870xD Sensors 84 Freescale Semiconductor Inc Figure 57 Data Flow For Measurements...
Page 171: ...FXTH870xD Sensors Freescale Semiconductor Inc 169 Figure 128 QFN Case Outline...
Page 172: ...FXTH870xD Sensors 170 Freescale Semiconductor Inc Figure 129 QFN Case Outline...
Page 173: ...FXTH870xD Sensors Freescale Semiconductor Inc 171...
