NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
FXTH87ERM
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Reference manual
Rev. 5.0 — 4 February 2019
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5.5.4 MCU on-chip peripheral modules in STOP modes
When the MCU enters any STOP mode, system clocks to the internal peripheral modules
except the wakeup timer and LFR detectors/decoder are stopped. Even in the exception
case (ENDBM = 1), where clocks are kept alive to the BACKGROUND debug logic,
clocks to the peripheral systems are halted to reduce power consumption.
5.5.4.1 I/O pins
If the MCU is configured to go into STOP1 mode, the I/O pins are forced to their default
reset state (Hi-Z) upon entry into stop. This means that the I/O input and output buffers
are turned off and the pullup is disconnected.
5.5.4.2 Memory
All module interface registers will be reset upon wakeup from STOP1 and the contents of
RAM are not preserved. The MCU must be initialized as upon reset. The contents of the
FLASH memory are non-volatile and are preserved in any of the STOP modes.
5.5.4.3 Parameter registers
The 64 bytes of parameter registers are kept active in all modes of operation as long as
power is applied to the supply pins. The contents of the parameter registers behave like
RAM and are unaffected by any reset.
5.5.4.4 LFO
The LFO remains active regardless of any mode of operation.
5.5.4.5 FRC
The Free-Running Counter can be enabled or halted. Once enabled and not halted, the
FRC remains active regardless of any mode of operation.
5.5.4.6 MFO
The medium frequency oscillator (MFO) will remain powered up when the MCU enters
the STOP mode only when the SMI has been initiated to make a pressure or acceleration
measurement; or when the RF transmitter’s state machine is processing data.
5.5.4.7 HFO
The HFO is halted in all STOP modes.
5.5.4.8 PWU
The PWU remains active regardless of any mode of operation.
5.5.4.9 ADC10
The internal asynchronous ADC10 clock is always used as the conversion clock. The
ADC10 can continue operation during STOP4 mode. Conversions can be initiated while
the MCU is the STOP4 mode. All ADC10 module registers contain their reset values
following exit from STOP1 mode
Section 14 "LF Receiver"
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