MMA8652FC datasheet(38/65 Pages) NXP

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MMA8652FC

Sensors

Freescale Semiconductor, Inc.

6.8.2

0x15: FF_MT_CFG Freefall/Motion Configuration register

This is the Freefall/Motion configuration register for setting up the conditions of the freefall or motion function.

Figure 14. FF_MT_CFG high-g and low-g threshold

Table 49. 0x15 FF_MT_CFG register (Read/Write)

Back to Register Address Map

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

ELE

OAE

ZEFE

YEFE

XEFE

—

Table 50. FF_MT_CFG register

Bit(s)

Field

Description

7ELE

Event Latch Enable: Event flags are latched into FF_MT_SRC register.

ELE denotes whether the enabled event flag will to be latched into the FF_MT_SRC register or whether the event flag

status in the FF_MT_SRC will indicate the real-time status of the event.

• If ELE bit is set to 1, then the event flags are frozen when the EA bit gets set, and the event flags are cleared by

reading the FF_MT_SRC source register.

• Reading the FF_MT_SRC register clears the event flag EA and all FF_MT_SRC bits.

0 Event flag latch disabled (default)

1 Event flag latch enabled

6OAE

Motion detect / Freefall detect flag selection

Selects between Motion (logical OR combination) and Freefall (logical AND combination) detection.

0 Freefall flag (Logical AND combination) (default)

1 Motion flag (Logical OR combination)

5ZEFE

Event flag enable on Z

ZHFE enables the detection of a motion or freefall event when the measured acceleration data on Z channel is beyond

the threshold set in FF_MT_THS register.

• If ELE bit (FF_MT_CFG register) is set to 1, then new event flags are blocked from updating the FF_MT_SRC

0 Event detection disabled (default)

1 Raise event flag on measured acceleration value beyond preset threshold

YEFE

Event flag enable on Y event

YEFE enables the detection of a motion or freefall event when the measured acceleration data on Y channel is beyond

the threshold set in FF_MT_THS register.

• If ELE bit (FF_MT_CFG register) is set to 1, then new event flags are blocked from updating the FF_MT_SRC

0 Event detection disabled (default)

1 Raise event flag on measured acceleration value beyond preset threshold

XEFE

Event flag enable on X event

XEFE enables the detection of a motion or freefall event when the measured acceleration data on X channel is beyond

the threshold set in FF_MT_THS register.

• If ELE bit (FF_MT_CFG register) is set to 1, then new event flags are blocked from updating the FF_MT_SRC

0 Event detection disabled (default)

1 Raise event flag on measured acceleration value beyond preset threshold

2–0

—

+8 g

High-g + Threshold (Motion)

Low-g Threshold (Freefall)

High-g – Threshold (Motion)

–8 g

X, Y, or Z High-g Region

X, Y, or Z Low-g Region

Negative

Positive

Acceleration

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