NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
15.9 RFM registers
The RFM contains twelve registers to control its functions and 32 registers to provide
access to the output data buffer.
15.9.1 RFM Control Register 0 — RFCR0
The RFCR0 register contains eight control bits for setting the output data rate of the RFM
as described in Table 133.
Table 133.ꢀRFM control register 0 (RFCR0) (address $0030)
Bit
R
7
6
5
4
3
2
1
0
BPS[7:0]
W
Reset
0
0
1
1
0
1
0
0
Table 134.ꢀRFCR0 field descriptions
Field
Description
Data Rate — The BPS[7:0] control bits select the data rate for the transmitted datagrams as described by
the following equation:
7–0
where:
BPS[7:0]
fDATA = Data rate in bits/second
fXTAL = External crystal frequency in Hz = 26 MHz
BPS = Value of data rate code (BPS[7:0])
Examples of the value for common data rates are given in Table 135. The BPS[7:0] control bits are set to
$34 by the RFMRST signal which results in a default data rate of 9600 bits/sec.
Table 135.ꢀData rate option examples
BPS[7:0]
Decimal Value
BPS[7:0] Decimal
Value
Data Rate
Data Rate
Target
Nominal
2000.0
2403.8
4000.0
4504.5
fXTAL = 26 MHz
Target
Nominal
4807.7
5000.0
9615.4
19230.8
fXTAL = 26 MHz
2000 bps
2400 bps
4000 bps
4500 bps
249
207
124
110
4800 bps
5000 bps
9600 bps
19200 bps
103
99
51
25
The BPS[7:0] bits are set to $34 by an RFMRST signal which results in a default data
rate of approximately 9600 bps.
15.10 RFM control register 1 — RFCR1
The RFCR1 register contains eight control bits for the RFM as described in Table 136.
FXTH87ERM
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Reference manual
Rev. 5.0 — 4 February 2019
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