AK8975 Datasheet, PDF (20/34 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

[AK8975/C]
7.2.2. WRITE Instruction
When the R/W bit is set to "0", AK8975/C performs write operation.
In write operation, AK8975/C 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
A7
A6
A5
A4
A3
A2
Figure 7.7 Register Address
LSB
A1
A0
After receiving the second byte (register address), AK8975/C generates an acknowledge then receives the
third byte.
The third and the following bytes represent control data. Control data consists of 8 bits and is based on the
MSB-first configuration. AK8975/C generates an acknowledge after every byte is received. Data transfer
always stops with a stop condition generated by the master.
MSB
D7 D6
D5
D4
D3
D2
Figure 7.8 Control Data
LSB
D1
D0
AK8975/C can write multiple bytes of data at a time.
After reception of the third byte (control data), AK8975/C 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.
The address is incremented from 00H to 0CH or from 10H to12H. When the address is in the range from 00H
to 0CH, the address goes back to 00H after 0CH. When the address is in the range from 10H to 12H, the
address goes back to 10H after 12H. Actual data is written only to Read/Write registers (0AH to 0FH).
SDA
S
T
A
R/W="0"
R
T
S
Slave
Address
Register
Address(n)
Data(n)
Data(n+1)
A
A
A
A
C
C
C
C
K
K
K
K
Figure 7.9 WRITE Instruction
S
T
O
P
Data(n+x)
P
A
A
C
C
K
K
MS1187-E-02
- 20 -
2010/05