AK8973 Datasheet, PDF (16/31 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

ASAHI KASEI
[AK8973]
7.2. WRITE Instruction
When the R/W bit is set to "0", AK8973 performs write operation.
In write operation, AK8973 generates an acknowledge after receiving a start condition and the first byte (slave
address) then receives the second byte. The second byte is used to specify the address of an internal control
register and is based on the MSB-first configuration.
MSB
LSB
A7
A6
A5
A4
A3
A2
A1
A0
Fig. 05 Register Address
After receiving the second byte (register address), AK8973 generates an acknowledge then receives the third
byte.
The third byte and after represent control data. Control data consists of 8 bits and is based on the MSB-first
configuration. AK8973 generates an acknowledge after every byte is received. Data transfer always stops with
a stop condition generated by the master.
MSB
LSB
D7
D6
D5
D4
D3
D2
D1
D0
Fig. 06 Control Data
AK8973 can write multiple bytes of data at a time.
After reception of the third byte (control data), AK8973 generates an acknowledge then receives the next data.
If additional data is received instead of a stop condition after receiving one byte of data, the address counter
inside the LSI chip is automatically incremented and the data is written at the next address.
If the writing of data starts at address "E0H", the write address changes from "E0H, E1H through E5H, E6H".
When "E6H" is exceeded, the internal address counter rolls over, and the following data is written in
sequentially starting at address "E0H" again.
SDA
S
T
A
R/W="0"
R
T
S
Slave
Address
Register
Address(n)
A
C
K
Data(n)
A
C
K
Data(n+1)
A
A
C
C
K
K
Fig. 07 WRITE Operation
S
T
O
P
Data(n+x)
P
A
A
C
C
K
K
MS0561-E-01 <Preliminary>
- 16 -
2007/01