[AK4627]
(2) I2C-bus Control Mode (I2C pin= “H”)
The AK4627 supports the fast-mode I2C-bus (max: 400kHz).
1. WRITE Operations
Figure 22 shows the data transfer sequence in I2C-bus mode. All commands are preceded by a START condition. A
HIGH to LOW transition on the SDA line while SCL is HIGH indicates a START condition (Figure 28). After the
START condition, a slave address is sent. This address is 7 bits long followed by the eighth bit which is a data
direction bit (R/W) (Figure 23). The most significant five bits of the slave address are fixed as “00100”. The next
two bits are CAD1 and CAD0 (device address bits). These two bits identify the specific device on the bus. The
hard-wired input pins (CAD1 pin and CAD0 pin) set these device address bits. If the slave address matches that of
the AK4627, the AK4627 generates an acknowledge and the operation is executed. R/W bit = “1” indicates that the
read operation is to be executed. “0” indicates that the write operation is to be executed.
The second byte consists of the address for control registers of the AK4627. The format is MSB first, and those most
significant 3-bits are fixed to zeros (Figure 24). Those data after the second byte contain control data. The format is
MSB first, 8bits (Figure 25). The AK4627 generates an acknowledge after each byte has been received. A data
transfer is always terminated by a STOP condition generated by the master. A LOW to HIGH transition on the SDA
line while SCL is HIGH defines a STOP condition (Figure 28).
The AK4627 is capable of more than one byte write operation by one sequence. After receipt of the third byte, the
AK4627 generates an acknowledge, and awaits the next data again. The master can transmit more than one byte
instead of terminating the write cycle after the first data byte is transferred. After the receipt of each data, the internal
5bits address counter is incremented by one, and the next data is taken into next address automatically. If the address
exceed 0DH prior to generating a stop condition, the address counter will “roll over” to 00H and the previous data
will be overwritten.
The data on the SDA line must be stable during the HIGH period of the clock. The HIGH or LOW state of the data
line can only be changed when the clock signal on the SCL line is LOW (Figure 30) except for the START and the
STOP condition.
S
S
T
O
P
T
A
R
T
R/W
Slave
Address
Sub
Address(n)
S
Data(n)
Data(n+1)
Data(n+x)
P
SDA
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
Figure 22. Data transfer sequence at the I2C-bus mode
0
0
0
1
0
0
CAD1 CAD0
R/W
(Those CAD1/0 should match with CAD1/0 pins)
Figure 23. The first byte
0
0
A4
A3
A2
D2
A1
D1
A0
D0
Figure 24. The second byte
D7
D6
D5
D4
D3
Figure 25. Byte structure after the second byte
MS1278-E-02
2012/03
- 32 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
