FXOS8700CQ datasheet(76/86 Pages) FREESCALE

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9.17.5

Magnetometer Vector Magnitude Function

The magnetometer vector magnitude function will generate an interrupt when

> M_VECM_THS value and t > M_VECM_CNT

value. Where m_x_out, m_y_out, and m_z_out are the current decimated magnetometer output values, and m_x_ref, m_y_ref,

and m_z_ref are the internally latched reference values. The user may program the M_VECM_THS and M_VECM_CNT registers

to establish the conditions needed to detect a magnetic vector magnitude change event. Depending on the values chosen for the

reference values, this function may be configured to detect a magnetic field magnitude that is above a preset threshold (with

reference values = 0), or a change in magnitude between two magnetic vectors greater than the preset threshold (with reference

values non-zero). Please note x_ref, y_ref, z_ref are stored internally and are not observable by the user through the register

interface. Please refer to Freescale application note AN4458.

9.17.6

M_VECM_CFG (0x69) register

src_m_drdy

Magnetic data-ready interrupt flag:

0: No new magnetic data is available.

1: New magnetic data is available.

—

m_vecm_ele

m_vecm_initm

m_vecm_updm

m_vecm_en

m_vecm_wake_en

m_vecm_init_en m_vecm_init_cfg

Figure 127. M_VECM_CFG register

Table 98. M_VECM_CFG bit descriptions

Field

Description

m_vecm_ele

Magnetic vector magnitude event latch enable:

0: Event latch disabled

1: Event latch enabled

With event latching enabled, the src_m_vecm interrupt flag may only be cleared by reading the M_INT_SRC register.

With event latching disabled, the src_m_vecm interrupt flag is updated in real time and may be cleared by the ASIC prior

to the user reading the flag.

m_vecm_initm

Magnetic vector magnitude initialization mode:

0: The ASIC uses the current magnetic output data as the initial reference values at the time the m_vecm_en bit is set.

1: The ASIC uses the data stored in the M_VECM_X/Y/Z_INIT registers as the initial reference values at the time the

m_vecm_en bit is set.

m_vecm_updm

Magnetic vector magnitude reference value update mode:

0: The function updates the reference values with the current X/Y/Z magnetic data when the event is triggered.

1: The function does not update the reference values when the event is triggered.

Setting m_vecm_initm = 1 and m_vecm_updm = 1 allows the user to manually update the reference values using the

M_VECM_INIT_X/Y/Z registers in real time when the function is enabled.

m_vecm_en

Magnetic vector magnitude function enable:

0: Function is disabled.

1: Function is enabled, the ASIC will update the internal m_x/y/z_ref registers with either the current magnetic output

data or the values stored in the M_VECM_INIT_X/Y/Z registers depending on the state of m_vecm_initm.

Note: The magnetic vector magnitude function will only function correctly up to a maximum ODR of 400 Hz.

m_vecm_wake_en

Magnetic vector magnitude wake enable:

0: The system excludes the src_m_vecm event flag when evaluating the Auto-Sleep function.

1: The system includes the src_m_vecm event flag when evaluating the Auto-Sleep function.

m_vecm_int_en

Magnetic vector magnitude interrupt enable:

0: Magnetic vector magnitude interrupt is disabled.

1: Magnetic vector magnitude interrupt is enabled.

m_vecm_init_cfg

Magnetic vector magnitude interrupt configuration:

0: Magnetic vector magnitude interrupt is output on INT2 pin.

1: Magnetic vector magnitude interrupt is output on INT1 pin.

Table 97. M_INT_SRC bit description

m_x_out

m_x_ref

–

()

m_y_out

m_y_ref

–

()

m_z_out

m_z_ref

–

()

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