AK8973 Datasheet, PDF (12/31 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

ASAHI KASEI
[AK8973]
6.2. Description of Each Operation Mode
6.2.1. Power-down Mode
Power to all internal circuits is turned off.
During power-down mode, measurement conditions for sensor measurement mode can be set by setting
adequate values to the registers.
The measurement conditions set in the registers are reset only by applying "L" signal to RSTN pin, and not by
a mode transition.
6.2.2. Sensor Measurement Mode
Measurement is made with the sequence below. When the measurement is completed, it transits to
power-down mode automatically.
<Timing Chart>
Measurement timing
Ttm Thm
T
H
Power-down mode
Ttm Thm
T
H
Power-down mode
Power-down mode
I/F-logic
INT bit
Write sensor measurement mode
Write sensor measurement mode
INT bit
Measured data read
Measured data read
Be sure to read measured data before starting the next measurement.
Ttm: Temperature sensor measurement period, Thm: Magnetic sensor measurement period
TSM: Ttm+Thm=12.56ms typ.
<Detailed Description>
When sensor measurement mode (MODE[1:0]="00") is set to register at power-down mode, AK8973 starts
measurement operation. First, temperature sensor and 3-axis magnetic sensor are measured in sequence,
automatically. Then, the measured data are stored in the following registers. Finally, AK8973 automatically
transits to power-down mode.
Temperature sensor output result Register
TMPS[7:0]
Magnetic sensor output result
Register
H1X[7:0], H1Y[7:0], H1Z[7:0]
When AK8973 returns to power-down mode, INT pin is driven to "H" to notify the external CPU that the
measurements have been finished. INT bit is placed in the same state.
When sensor output results are read, INT pin is driven to "L". For the fall timing of INT pin, refer to "6.3.
Interrupt Function based on INT Pin". On the falling edge of INT pin, INT bit also returns to "0".
When the external CPU confirmed that INT pin is driven to "H" or INT bit is set to "1", it should recognize that
the sensor measurements are completed, and then read the mentioned 4-byte data of sensor output results.
<Note>
To execute the sensor measurement mode, INT pin must be "L" or INT bit must be "0". Before executing this
pattern, check that INT pin is "L" or INT bit is "0", or drive INT pin to "L" by performing data register read
operation as dummy. An attempt to set the sensor measurement mode when the INT pin is high is ignored.
Also when the transition of power-down mode is set to the sensor measurement mode or EEPROM access
mode, the contents of magnetic sensor output results of H1X[7:0], H1Y[7:0], and H1Z[7:0] are reset.
MS0561-E-01 <Preliminary>
- 12 -
2007/01