AK09912 Datasheet, PDF (20/42 Pages) HuaXinAn Electronics CO.,LTD – 3-axis Electronic Compass

[AK09912]
6.4.3.6. Magnetic Sensor Overflow
AK09912 has the limitation for measurement range that the sum of absolute values of each axis should be smaller than 4912
µT.
|X|+|Y|+|Z| < 4912 µT
When the magnetic field exceeded this limitation, data stored at measurement data are not correct. This is called Magnetic
Sensor Overflow.
When magnetic sensor overflow occurs, HOFL bit turns to “1”. When the next measurement starts, it returns to “0”.
6.4.4. External Trigger Measurement Mode
When External trigger measurement mode (MODE[4:0]=“01010”) is set, AK09912 waits for trigger input. When a pulse is
input from TRG pin, magnetic sensor measurement is started on the rising edge of TRG pin. After magnetic sensor
measurement and signal processing is finished, measurement magnetic data is stored to measurement data registers (HXL to
HZH) and all circuits except for the minimum circuit required for trigger input waiting are turned off (PD state). When the
next pulse is input, AK09912 wakes up automatically from PD and starts measurement again.
When temperature sensor is enabled (TEM =“1”), temperature sensor measurement is started together with magnetic sensor
measurement, and measurement temperature data is stored to measurement data registers (TMPS).
When power-down mode (MODE[4:0]=“00000”) is set, External trigger measurement mode ends. AK09912 keeps waiting
for the trigger input until the Power-down mode is set.
When External trigger measurement mode (MODE[4:0]=“01010”) is set again while AK09912 is already in External trigger
measurement mode, it starts to wait for the trigger input again. The trigger input is ignored while sensor is measuring.
Data read sequence and functions of read-only registers in External trigger measurement mode are the same as Continuous
measurement mode.
6.4.5. Self-test Mode
Self-test mode is used to check if the magnetic sensor is working normally.
When Self-test mode (MODE[4:0]=“10000”) is set, magnetic field is generated by the internal magnetic source and
magnetic sensor is measured. Measurement data is stored to measurement data registers (HXL to HZH), then AK09912
transits to Power-down mode automatically.(Temperature sensor is not measured.)
Data read sequence and functions of read-only registers in Self-test mode are the same as Single measurement mode.
6.4.5.1. Self-test Sequence
(1) Set Power-down mode. (MODE[4:0]=“00000”)
(2) Set Self-test mode. (MODE[4:0]=“10000”)
(3) Check Data Ready or not by any of the following method.
 Polling DRDY bit of ST1 register
 Monitor DRDY pin
When Data Ready, proceed to the next step.
(4) Read measurement data (HXL to HZH)
6.4.5.2. Self-test Judgment
When measurement data read by the above sequence is in the range of following table after sensitivity adjustment (refer to
8.3.13), AK09912 is working normally.
Criteria
HX[15:0]
-200 ≤ HX ≤ +200
HY[15:0]
-200 ≤ HY ≤ +200
HZ[15:0]
-1600 ≤ HZ ≤ -400
6.4.6. Fuse ROM Access Mode
Fuse ROM access mode is used to read Fuse ROM data. Sensitivity adjustment data for each axis is stored in Fuse ROM.
Set Fuse ROM Access mode (MODE[4:0]=“11111”) before reading Fuse ROM data. When Fuse ROM Access mode is set,
circuits required for reading Fuse ROM are turned on. However, it needs 100µs (Twatr) to read Fuse ROM after mode
setting.
After reading Fuse ROM data, set Power-down mode (MODE[4:0]=“00000”) before the transition to another mode.
MS1547-E-02
- 20 -
2014/7