MMA8652FC datasheet(49/77 Pages) FREESCALE

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MMA8652FC

Sensors

Freescale Semiconductor, Inc.

6.10

Transient configuration and status registers

For more information about the uses of the transient function, see application note AN4083, Data Manipulation and Basic

Settings for Xtrinsic MMA865xFC Accelerometers. This Transient (HPF) acceleration detection function is similar to the motion

detection function, except that high-pass filtered data is compared.

There is an option to disable the high-pass filter through the function. In this case, the behavior is the same as the motion

detection. This allows for the device to have two motion detection functions.

6.10.1

0x1D: Transient_CFG register

The transient detection mechanism can be configured to raise an interrupt when the magnitude of the high-pass filtered

acceleration threshold is exceeded. The TRANSIENT_CFG register is used to enable the transient interrupt generation

mechanism for the three axes (X, Y, Z) of acceleration. There is also an option to bypass the high-pass filter. When the high-pass

filter is bypassed, the function behaves similar to the motion detection.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

—

ELE

ZTEFE

YTEFE

XTEFE

HPF_BYP

Figure 41. 0x1D TRANSIENT_CFG register (Read/Write)

Table 40. TRANSIENT_CFG register

Bit(s)

Field

Description

Notes

4ELE

Transient event flags are latched into the TRANSIENT_SRC

Reading of the TRANSIENT_SRC register clears the event flag.

0 Event flag latch disabled (default)

1 Event flag latch enabled

ZTEFE

Event flag enable for Z-transient acceleration greater than a

transient threshold event.

0 Event detection disabled (default)

1 Raise event flag on measured acceleration delta

value that is greater than a transient threshold.

YTEFE

Event flag enable for Y-transient acceleration greater than a

transient threshold event.

XTEFE

Event flag enable for X-transient acceleration greater than

a transient threshold event.

0HPF_BYP

Bypass high-pass filter

0 Data to transient acceleration detection block is through HPF

(default)

1 Data to transient acceleration detection block is NOT through

HPF (similar to motion detection function)

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