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
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Field Description
2:0
LFCPT
AZ[2:0]
LFCPTAZ[2:0] – LF Auto Zero Counter Selection
Applications to set these bits to 1 1 0 for proper LF operation. These bits tune the minimum number of data
edges between two auto-zero requests during a data frame.
1 0 0 = Result of power on or LFR reset. Existing state remains after all other reset types.
10.15.17.12 LF receiver control A register (LFCTRLA)
Table 98. LF receiver control A register (LFCTRLA) (address $002C)
Bit 7 6 5 4 3 2 1 0
R
W
reserved reserved reserved reserved LFCC3 LFCC2 LFCC1 LFCC0
Reset U U U U U U U U
POR ($00) 0 0 0 0 0 0 0 0
LFR soft
reset ($00)
0 0 0 0 0 0 0 0
Table 99. LFCTRLA register field descriptions
Field Description
3:0
LFCC[3:0]
LFCC[3:0] – LF Successive Carrier Validations Counter Results
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.
The LFCC register is considered reset in data mode. The first carrier validation will lead to startup 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 CARMOD = 0 or TOGMOD = 1.
0 0 0 0 = Result of power on or LFR reset. Existing state remains after all other reset types.
10.16 Radio frequency (RF) transmitter 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 RF module (RFM) consists of an 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 RF transmitter module has the following features:
• Interframe
– Interframe generated by a combination of BASE, INCR & RAND parameters
– Incorporates an 7bit LFSR PRBS (random) generator
– Used to randomize the time interval between repeated TX sequences
• Frac-N MASH3 Modulator
– 4-bit integer (Fixed) and 13-bit fractional range
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