ISM303DAC datasheet(25/80 Pages) STMICROELECTRONICS

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ISM303DAC

Functionality

4.1.3

Magnetometer interrupt

In LSM303AH magnetometer interrupt signal generation is based on the comparison

between data and a programmable threshold.

To enable the interrupt function, in INT_CTRL_REG_M register (63h) the "IEN" bit must be

set to '1'.

In the LSM303AH the user can select the axis/axes in which the interrupt function can be

enabled. In order to do this, the XIEN, YIEN, and ZIEN bits in INT_CTRL_REG_M (63h)

need be set properly.

The threshold value can be programmed by setting the INT_THS_L_REG_M (65h) and

INT_THS_H_REG_M (66h) registers.

The threshold is expressed in absolute value as a 15-bit unsigned number. The threshold

has the same sensitivity as the magnetic data.

When magnetic data exceeds the positive or the negative threshold, the interrupt signal is

generated and the information about the type of interrupt is stored in the

INT_SOURCE_REG_M (64h) register. In particular, when magnetic data exceeds the

positive threshold the P_TH_S_axis bit is set to '1', while if data exceeds the negative

threshold the N_TH_S_axis bit is set to '1'. If magnetic data lay between the positive and the

negative thresholds, no interrupt signal is released.

Figure 5. Interrupt function

Two different approaches for the interrupt function are available:



Typical: comparison is between magnetic data read by the sensor and the

programmable threshold;



Advanced: comparison is made between magnetic data after hard-iron correction and

the programmable threshold.

These approaches are configurable by setting the INT_on_DataOFF bit in CFG_REG_B_M

(61h).

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