AK8963N Datasheet, PDF (15/38 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

[AK8963]
6.4.3. Continuous Measurement Mode 1 and 2
When continuous measurement mode 1 (MODE[3:0]=“0010”) or 2 (MODE[3:0]=“0110”) is set, sensor is
measured periodically at 8Hz or 100Hz respectively. When sensor measurement and signal processing is
finished, measurement data is stored to measurement data registers (HXL ~ HZH) and all circuits except for
the minimum circuit required for counting cycle lentgh are turned off (PD). When the next measurement
timing comes, AK8963 wakes up automatically from PD and starts measurement again.
Continuous measurement mode ends when power-down mode (MODE[3:0]=“0000”) is set. It repeats
measurement until power-down mode is set.
When continuous measurement mode 1 (MODE[3:0]=“0010”) or 2 (MODE[3:0]= “0110”) is set again while
AK8963 is already in continuous measurement mode, a new measurement starts. ST1, ST2 and measurement
data registers (HXL ~ HZH) will not be initialized by this.
(N-1)th
Nth
(N+1)th
PD
Measurement
PD
Measurement
PD
8Hz or 100Hz
Figure 6.4 Continuous measurement mode
6.4.3.1. Data Ready
When measurement data is stored and ready to be read, DRDY bit in ST1 register turnes to “1”. This is called
“Data Ready”. DRDY pin is in the same state as DRDY bit. When measurement is performed correctly,
AK8963 becomes Data Ready on transition to PD after measurement.
6.4.3.2. Normal Read Sequence
(1) 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.
(2) Read ST1 register (not needed when polling ST1)
DRDY: Shows Data Ready or not. Not when “0”, Data Ready when “1”.
DOR:
Shows if any data has been skipped before the current data or not. There are no skipped data
when “0”, there are skipped data when “1”.
(3) Read measurement data
When any of measurement data register (HXL ~ HZH) or ST2 register is read, AK8963 judges that data
reading is started. When data reading is started, DRDY bit and DOR bit turnes to “0”.
(4) Read ST2 register (required)
HOFL: Shows if magnetic sensor is overflown or not. “0” means not overflown, “1” means
overflown.
When ST2 register is read, AK8963 judges that data reading is finished. Stored measurement data is
protected during data reading and data is not updated. By reading ST2 register, this protection is released.
It is required to read ST2 register after data reading.
MS1356-E-02
- 15 -
2013/10