FXOS8700CQ datasheet(48/86 Pages) FREESCALE

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Sensors

Freescale Semiconductor, Inc.

9.9.3

A_FFMT_THS (0x17), A_FFMT_ THS_X_MSB (0x73), A_FFMT_THS_X_LSB (0x74),

A_FFMT_THS_Y_MSB (0x75), A_FFMT_THS_Y_LSB (0x76), A_FFMT_THS_Z_MSB

(0x77), A_FFMT_THS_Z_LSB (0x78) registers

Freefall/motion detection threshold registers.

a_ffmt_zhp

Z-high event polarity flag. Default value: 0

0: Z event was positive g

1: Z event was negative g

This bit read always zero if the a_ffmt_zefe control bit is set to zero

a_ffmt_yhe

Y-high event flag. Default value: 0

0: No event detected

1: Y-high event has been detected

This bit read always zero if the a_ffmt_yefe control bit is set to zero

a_ffmt_yhp

Y-high event polarity flag. Default value: 0

0: Y event detected was positive g

1: Y event was negative g

This bit always reads zero if the a_ffmt_yefe control bit is set to zero

a_ffmt_xhe

X-high event flag. Default value: 0

0: No event detected

1: X-high event has been detected

This bit always reads zero if the a_ffmt_xefe control bit is set to zero

a_ffmt_xhp

X-high event polarity flag. Default value: 0

0: X event was positive g

1: X event was negative g

This bit always reads zero if the a_ffmt_xefe control bit is set to zero

a_ffmt_dbcntm

ths[6:0]

0b0000000

Figure 46. A_FFMT_THS (0x17) register

Table 50. A_FFMT_THS (0x17) bit descriptions

Field

Description

a_ffmt_dbcntm

The ASIC uses a_ffmt_dbcntm to set the acceleration FFMT debounce counter clear mode independent of the value of

the a_ffmt_ths_xyz_en.

a_ffmt_dbcntm bit configures the way in which the debounce counter is reset when the inertial event of interest is

momentarily not true.

When a_ffmt_dbcntm bit is a logic ‘1’, the debounce counter is cleared to 0 whenever the inertial event of interest is no

longer true (part b, Figure 55) while if the a_ffmt_dbcntm bit is set to logic ‘0’ the debounce counter is decremented by 1

whenever the inertial event of interest in longer true

(part c, Figure 55) until the debounce counter reaches 0 or the inertial event of interest become active.

The decrementing of the debounce counter acts to filter out irregular spurious events which might impede the correct

detection of inertial events.

ths[6:0]

Freefall/motion detection threshold: default value: 0b0000000. Resolution is fixed at 63 mg/LSB.

a_ffmt_ths_xyz_en

a_ffmt_ths_x[12:6]

0b0000000

Figure 47. A_FFMT_THS_X_MSB (0x73) register

Table 49. A_FFMT_SRC bit descriptions

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