NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
a TPMS frame, a timeout will turn off the LFR module. This timeout can be program
through TIMOUT bit the LFCTL4 register.
LFEN = 0 or SRES
Disabled
(at any state)
LFEN = 1
yes
LFCDF
no
3
Analog powerup
T
= 2 LFO cycles
PU
No signal above
sensitivity threshold
Sniff for carrier
Frequency error
ON time completed
Signal above threshold
AND VALEN = 1
1
Signal above threshold
AND VALEN = 0
Wait OFF time
(= Tsampling - Ton)
Frequency and
duration check
LFCDTM
not reached
ON time completed
ON time completed
2
Frequency and
LFCDTM duration check
no
TOGMOD
Carrier validated
yes
CARMOD = 1
Invert CARMOD
CARMOD = 0
CARMOD = 0
AND DECEN = 1
AND DECEN = 0
Increment carrier counter
Start timeout
Rise carrier detect flag
Start analog demod chain
Start analog demode chain
Carrier counter ?LFSCC +1
T
DEC
Carrier counter = LFCC +1
No SYNC detected
ID not complete
Search for SYNC
SYNC detected
Rise carrier detect flag
Continously ON
yes
no
no
Timeout
Decode ID
1
Correct ID
Rise ID flag
Wrong ID
TOGMOD
yes
Error in first bit
yes
Decode data
Invert CARMOD
Error Error
Error in first bit
Rise error and EOM flag
Rise error flag
Data ready flag
yes
Continously ON
no
Rise OVF flags
no
Rise data, ready flag
ONMODE
y
es
no
ON time completed
no
Switch off
5 LFO cycles
yes
Rise ID flag
Tsampling completed
2
1
aaa-028020
Figure 27.ꢀFXTH87E LFR state machine diagram
FXTH87ERM
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Reference manual
Rev. 5.0 — 4 February 2019
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