FXLS8964AF datasheet(31/98 Pages) NXP

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NXP Semiconductors

FXLS8964AF

3-Axis Low-g Accelerometer

FXLS8964AF

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Objective data sheet

Rev. 2 — 30 October 2020

31 / 98

TFLT-MOT_DET

Figure 21. BOOT2 sequence and One-wire motion-detection protocol diagram (BT_MODE = VDD)

Table 16. BOOT2 sequence and One-wire motion protocol phase descriptions

Protocol phase

Description

VDD supply is not present (VDD < VDDmin); MCU and FXLS8964AF are both OFF; all IO pins

are floating/high-z.

VDD ≥ VDDmin; MCU and FXLS8964AF are turned on; FXLS8964AF performs the BOOT

sequence. During this phase, the MOT_DET input and BOOT_OUT open-drain output

functions are enabled. FXLS8964AF turns on the BOOT_OUT output for TPULSE-BOOT2 ms.

Note that the BOOT_OUT pulse will not be observable in the wired-AND configuration as it is

assumed the host MCU has not yet enabled the pull-up resistor on the MOT_DET and BOOT_

OUT pins (one pull-up resistor for both pins).

FXLS8964AF enters Hibernate mode directly after the BOOT sequence if the MCU has not

yet asserted the MOT_DET pin. During this phase, FXLS8964AF MOT_DET pin input function

remains enabled, waiting for the MOT_DET pin to go high, which will trigger an exit from this

mode.

The MCU asserts the MOT_DET pin high by enabling the pull-up; FXLS8964AF exits

Hibernate mode and performs the BOOT sequence. Anytime within TPULSE-WIN ms after the

BOOT_OUT pulse rising edge (measured from the VOL point), the host MCU may pulse the

MOT_DET line low to signal the desired motion detection threshold selection. If no pulse is

seen within this window, the default TPULSE-THRES0 threshold value is used. The available

pulse selections are shown in Table 17. The pulse is only recognized if it begins and ends

within the TPULSE-WIN ms period after the BOOT_OUT pulse rising edge, and also conforms to

the min and max values as shown in Table 17. If an invalid pulse width is observed, it will be

ignored and the default threshold value used instead.

Motion detection phase: FXLS8964AF continually scans for motion at the preconfigured ODR.

If the motion threshold and debounce criteria are met, a TPULSE-MOT ms pulse is signaled on

the MOT_DET pin (Open-Drain output is turned on). During this phase, the host may also

communicate with FXLS8964AF over the I2C or SPI interfaces.

Hibernate mode: When motion detection is no longer needed, the host MCU drives MOT_DET

low forcing FXLS8964AF into Hibernate mode to conserve power. FXLS8964AF delays the

entry into Hibernate mode for TMOT-HIB ms after the MOT_DET pin is brought low to debounce

the line.

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