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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Table 84. LFS register field descriptions
Field Description
7
LFDRF
LFDRF – LF Data Ready Flag
This read-only status flag is set when a complete byte of data has been received by the LFR. An interrupt
is sent to the MCU if the LFDRIE bit is set. Clear LFDRF by writing a one to the LFIAK bit or reading the
LFDATA register.
0 = No new data in LFDATA register; Result of power on or LFR reset. Existing state remains after all other
reset types.
1 = A new byte of data has been received and can be read from the LFDATA register.
6
LFERF
LFERF – LF Receive Error Flag
In data receive mode, this read-only status flag is set when a non-standard bit time is detected in the
Manchester data mode, when an incorrect ID is received or when a sampling error has been detected. Any
received data bits before the error occurs are placed in the data buffer. In carrier detect mode, this read-
only status flag is not used and remains clear. An interrupt is sent to the MCU if the LFERIE bit is set. Clear
LFERF by writing a one to the LFIAK bit.
0 = Normal operation; Result of power on or LFR reset. Existing state remains after all other reset types.
1 = Error detected in the Manchester data mode, when an incorrect ID is received or when a sampling error
has been detected.
5
LFCDF
LFCDF – LF Carrier Pulse Detect Flag
In carrier detect mode, this read-only status flag is set when the number of consecutive carrier validations
set by the LFCC bits in is reached. Note that the LFCC function is not working if TOGMOD = 1 or if
CARMOD = 1. Clear LFCDF by writing a one to the LFIAK bit.
0 = Normal operation; Result of power on or LFR reset. Existing state remains after all other reset types.
1 = Carrier detection has occurred.
4
LFIDF
LFIDF – LF ID Detect Flag
In data receive mode, this read-only status flag is set when the received ID matches the stored value. This
interrupt can be generated even if no data bits follow the ID. An interrupt is sent to the MCU if the LFIDIE bit
is set. Clear LFIDF by writing a one to the LFIAK bit.
0 = Normal operation; Result of power on or LFR reset. Existing state remains after all other reset types.
1 = wake-up ID has been detected.
3
LFOVF
LFOVF – LF Receive Data Overflow Flag
In data receive mode, this read-only status flag is set when a complete byte of data has been received and
written into the LFDATA register, but the previously received byte was not read from LFDATA register yet.
This indicates that the MCU has lost the previously received data byte. In carrier detect mode, this read-
only status flag is not used and remains cleared. No separate interrupt is generated by this specific flag bit
because the LFDRF flag would serve that purpose. Clear LFOVF by writing a one to the LFIAK bit.
0 = Normal operation; Result of power on or LFR reset. Existing state remains after all other reset types.
1 = Previous data over-written before MCU read it.
2
LFEOMF
LFEOMF – LF Receive Data End of Message Flag
In data receive mode, this read-only status flag is set when a complete byte of data has been received
and written into the LFDATA register and an end-of-message Manchester encoding error occurs. In carrier
detect mode, this read-only status flag is not used and remains clear. No interrupt is generated by this flag
bit because the LFERF flag would serve that purpose. Clear LFEOMF by writing a one to the LFIAK bit.
0 = No EOM detected; Result of power on or LFR reset. Existing state remains after all other reset types.
1 = EOM detected.
1
LPSM
LPSM = Low Power Sniff Mode
This bit used to activate the low power consumption during SNIFF mode. It saves approximately 1 μA with a
trade-off of an additional 300 µs in transition from carrier to data mode.
0 = Low time transition from carrier to data mode
1 = Low consumption during sniff mode; Result of power on or LFR reset. Existing state remains after all
other reset types.
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