NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
= Reserved
Table 130.ꢀLFCTRLA register field descriptions
Field
Description
7-4
Reserved bits — Not for user access.
Reserved
LF Successive Carrier Validations Counter — The value of the LFCC[3:0] bits define how many times the
carrier detect sample ON time detected an LF carrier signal before the LFCDF flag bit set. The flag will be
risen when the number of ON samples with a detected carrier greater than the LFCDTM[3:0] reaches the
value of the LFCC[3:0] bits plus one. The internal count of detected carrier pulses will increment the count
as long as they are consecutive samples. When a sample is encountered without any detected carrier the
count will be reset.
3-0
LFCC[3:0]
The LFCC register is considered reset in data mode. The first carrier validation will lead to start up of the
receiver chain.
This feature allows the user to define a number of consecutive carrier detections are required before the
flag is risen; and is useful in detecting long duration carrier pulses.
This counter is disabled if TOGMOD = 1.
15 RF module
It is not intended that the RFM may be actively powered up and/or transmitting RF data
while physical parameter measurements are being made; or during the time that the LFR
may be actively receiving/decoding LF signals. The resulting interactions will degrade the
performance of the RF output spectrum.
The FXTH87E consists of an RF module (RFM) with external crystal-driven oscillator,
VCO, fractal-n PLL and RF output amplifier (PA) for an antenna. It also contains a small
state machine controller, random time generator and hardware data buffer for automated
output or direct control from the MCU. The overall block diagram is shown in Figure 37.
FXTH87ERM
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© NXP B.V. 2019. All rights reserved.
Reference manual
Rev. 5.0 — 4 February 2019
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