
ASAHI KASEI 
[AK4702] 
MS0187-E-00 
2002/11 
- 22 - 
n
 Mode Control Interface 
I
2
C-bus Control Mode 
The AK4702 supports the standard-mode I
2
C-bus (max: 100kHz). Then AK4702 doesn’t support the fast-mode I
2
C-bus 
system (max: 400kHz). 
1. WRITE Operations 
Figure 8 shows the data transfer sequence in I
2
C-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 14). After the START 
condition, a slave address is sent. This address is 7 bits long followed by an eighth bit which is a data direction bit (R/W). 
The most significant seven bits of the slave address are fixed as “0010001”. If the slave address match that of the AK4702, 
the AK4702 generates the acknowledge and the operation is executed. The master must generate the acknowledge-related 
clock pulse and release the SDA line (HIGH) during the acknowledge clock pulse (Figure 15). A “1” for R/W bit indicates 
that the read operation is to be executed. A “0” indicates that the write operation is to be executed. The second byte consists 
of the address for control registers of the AK4702. The format is MSB first, and those most significant 3-bits are fixed to 
zeros (Figure 10). The data after the second byte contain control data. The format is MSB first, 8bits (Figure 11). The 
AK4702 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 14). 
The AK4702 can execute multiple one byte write operations in a sequence. After receipt of the third byte, the AK4702 
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 address counter 
is incremented by one, and the next data is taken into next address automatically. If the address exceeds 08H prior to 
generating the 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 change when the clock signal on the SCL line is LOW (Figure 16) except for the START and the STOP condition. 
S
T
A
R
T
Slave
Address
Address(n)
SDA
A
C
K
A
C
K
S
A
C
K
Sub
Data(n)
P
S
T
O
P
Data(n+x)
A
C
K
Data(n+1)
A
C
K
R/W= “0”
A
C
K
Figure 8. Data transfer sequence at the I
2
C-bus mode 
0 
0 
1 
0 
0 
0 
1 
R/W 
Figure 9. The first byte 
0 
0 
0 
A4 
A3 
A2 
A1 
A0 
Figure 10. The second byte 
D7 
D6 
D5 
D4 
D3 
D2 
D1 
D0 
Figure 11. Byte structure after the second byte