[AK09918]
9.4.3.2. Normal Read Sequence
(1) Check Data Ready or not by polling DRDY bit of ST1 register
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”.
(2) Read measurement data
When any of measurement data register (HXL to TMPS) or ST2 register is read, AK09918 judges
that data reading is started. When data reading is started, DRDY bit and DOR bit turns to “0”.
(3) Read ST2 register (required)
HOFL: Shows if magnetic sensor is overflowed or not. “0” means not overflowed, “1” means
overflowed.
When ST2 register is read, AK09918 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.
(N-1)th Nth
(N+1)th
PD
Measurement
PD
Measurement
PD
Internal Buffer
(N-1)th
Nth
(N+1)th
Measurement Data Register
(N-1)th
Nth
(N+1)th
DRDY
Data read
ST1 Data(N)
ST2
ST1 Data(N+1)
ST2
Figure 9.5. Normal read sequence
9.4.3.3. Data Read Start during Measurement
When sensor is measuring (Measurement period), measurement data registers (HXL to TMPS) keep the
previous data. Therefore, it is possible to read out data even in measurement period. If data is started to be
read during measurement period, previous data is read.
(N-1)th Nth
(N+1)th
PD
Measurement
PD
Measurement
PD
Internal Buffer
(N-1)th
Nth
(N+1)th
Measurement Data Register
(N-1)th
Nth
DRDY changes to "1"
because read-out becomes possible.
DRDY
Data read
ST1 Data(N)
ST2
ST1 Data(N)
ST2
Figure 9.6. Data read start during measurement
016014242-E-00
2016/11
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AKM [ ASAHI KASEI MICROSYSTEMS ]
