MAG3110_12 Datasheet, PDF (11/28 Pages) Freescale Semiconductor, Inc – Three-Axis, Digital Magnetometer

4.3.5 INT1
The DR_STATUS register (see section 5.1.1) contains the ZYXDR bit which denotes the presence of new measurement data on
one or more axes. Software polling can be used to detect the transition of the ZYXDR bit from 0 to 1 but, since the ZYXDR bit is
also logically connected to the INT1 pin, a more efficient approach is to use INT1 to trigger a software interrupt when new
measurement data is available as follows:
1. Enable automatic resets by setting AUTO_MRST_EN bit in CTRL_REG2 (CTRL_REG2 = 0b1XXXXXX).
2. Put MAG3110 in ACTIVE mode (CTRL_REG1 = 0bXXXXXX01).
3. Idle until INT1 goes HIGH and activates an interrupt service routine in the user software.
4. Read magnetometer data as required from registers 0x01 to 0x06. INT1 is cleared when register 0x01 OUT_X_MSB is
read and this register must therefore always be read in the interrupt service routine.
5. Return to idle in step 3.
4.3.6 Triggered Measurements
Set the TM bit in CTRL_REG1 when you want the part to acquire only 1 sample on each axis. See table below for details.
AC
TM
Description
0
0
ASIC is in low power standby mode.
The ASIC will exit standby mode, perform one measurement cycle based on the
0
1
programmed ODR and OSR setting, update the I²C data registers and re- enter
standby mode.
The ASIC will perform continuous measurements based on the current OSR and
1
0
ODR settings.
The ASIC will continue the current measurement at the fastest applicable ODR
1
1
for the user programmed OSR. The ASIC will return back to the programmed
ODR after completing the triggered measurement.
The anti-aliasing filter in the A/D converter has a finite delay before the output “settles”. The output data for the first ODR period
after getting out of Standby mode is expected to be slightly off. This effect will be more pronounced for the lower over-sampling
settings since with higher settings the error of the first acquisition will be averaged over the total number of samples. Therefore,
it is not recommended to use TRIGGER MODE (CTRL_REG1[AC]=0, CTRL_REG1[TM]=1) measurements for applications that
require high accuracy, especially with low over-sampling settings.
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Freescale Semiconductor, Inc.
MAG3110
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