[AK8975/C]
6.4.3. Self-test
Mode
Self-test mode is used to check if the sensor is working normally.
When self-test mode (MODE[3:0]=“1000”) is set, magnetic field is generated by the internal magnetic source
and sensor is measured. Measurement data is stored to measurement data registers (HXL to HZH), then
AK8975/C transits to power-down mode automatically.
Before setting self-test mode, write “1” to SELF bit of ASTC register. Data read sequence and functions of
read-only registers in self-test mode is the same as single measurement mode.
When self-test is end, write “0” to SELF bit then proceed to other operation.
<Self-test Sequence>
(1)
Set Power-down mode
(2)
Write “1” to SELF bit of ASTC register
(3)
Set Self-test Mode
(4)
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.
(5)
Read measurement data (HXL to HZH)
(6)
Write “0” to SELF bit of ASTC register
<Self-test Judgement>
When measurement data read by the above sequence is in the range of following table after sensitivity
adjustment (refer to 8.3.11), AK8975/C is working normally.
HX[15:0] HY[15:0] HZ[15:0]
Criteria -100
≤
X
≤
+100 -100
≤
Y
≤
+100 -1000
≤
Z
≤
-300
6.4.4. 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. These data are used in calculation of direction by the external CPU.
When Fuse ROM mode (MODE[3:0]=“1111”) is set, circuits reauired for reading fuse ROM are turned on.
After reading fuse ROM data, set power-down mode (MODE[3:0]=“0000”).
MS1187-E-02
- 15 -
2010/05
