AK8975 Datasheet, PDF (13/34 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

[AK8975/C]
6.4. Description of Each Operation Mode


6.4.1. Power-down Mode
Power to all internal circuits is turned off. All registers except fuse ROM are accessible in power-down mode.
Data stored in read/write registers are remained.
6.4.2. Single Measurement Mode
When single measurement mode (MODE[3:0]=“0001”) is set, sensor is measured, and after sensor
measurement and signal processing is finished, measurement data is stored to measurement data registers
(HXL to HZH), then AK8975/C transits to power-down mode automatically. On transition to power-down
mode, MODE[3:0] turns to “0000”. At the same time, DRDY bit in ST1 register turns to “1”. This is called
“Data Ready”. When any of measurement data register (HXL to HZH) or ST2 register is read, or operation
mode is changed from power-down mode to other mode, DRDY bit turns to “0”. DRDY pin is in the same state
as DRDY bit.
Operation Mode: Single measuremnet
Power-down
(1)
(2)
(3)
Measurement period
Measurement Data Register
Last Data
IndefiniteMeasurement Data (1) IndefiniteData(2)
IndefiniteData(3)
DRDY
Register Read
Data Register
Data Register
Register Write MODE[3:0]="0001"
MODE[3:0]="0001" MODE[3:0]="0001"


Figure 6.2 Single measurement mode
6.4.2.1. Data Ready
When measurement data is stored and ready to be read, DRDY bit in ST1 register turns to “1”. This is called
“Data Ready”. DRDY pin is in the same state as DRDY bit. When measurement is performed correctly,
AK8975/C becomes Data Ready on transition to Power-down mode (PD) after measurement. The period from
the end of Nth measurement to the start of (N+1)th measurement is called “Data Readable Period”. Stored
measurement data should be read during Data Readable Period.
(N-1)th
PD
Nth
(N+1)th
Measurement
Measurement
PD
PD
Data Readable Period
Figure 6.3 Data Readable Period
Data Readable Period

MS1187-E-02
- 13 -
2010/05