AK8157A Datasheet, PDF (16/26 Pages) Asahi Kasei Microsystems – Multiclock Generator for Premium Audio Device

[AK8157A]
■ Register Control Interface
I²C-bus Control Mode
The AK8157A supports the fast-mode I²C-bus (max: 400kHz, Ver 1.0).
1. WRITE Operations
Figure 11 shows the data transfer sequence for the 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 17). After the START condition, a slave address is sent. This address is 7 bits long
followed by the eighth bit that is a data direction bit (R/W). The most significant five bits of the slave
address are fixed as “00100”. The next bits are CAD1 and CAD0 (device address bits). This bit identifies
the specific device on the bus. The hard-wired input pin (CAD1pins, CAD0 pin) sets these device address
bits (Figure 12). If the slave address matches that of the AK8157A, the AK8157A generates an
acknowledgement and the operation is executed. The master must generate the acknowledgement
-related clock pulse and release the SDA line (HIGH) during the acknowledgement clock pulse (Figure
18). A R/W bit value of “1” indicates that the read operation is to be executed, and “0” indicates that the
write operation is to be executed.
The second byte consists of the control register address of the AK8157A and the format is MSB first.
(Figure 13). The data after the second byte contains control data. The format is MSB first, 8bits (Figure
14). The AK8157A generates an acknowledgement after each byte is received. 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 17).
The AK8157A can perform more than one byte write operation per sequence. After receipt of the third
byte the AK8157A generates an acknowledgement and awaits the next data. The master can transmit
more than one byte instead of terminating the write cycle after the first data byte is transferred. After
receiving each data packet the internal address counter is incremented by one, and the next data is
automatically taken into the next address. If the address exceeds “01H” 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 remain stable during the HIGH period of the clock. HIGH or LOW state of
the data line can only be changed when the clock signal on the SCL line is LOW (Figure 19) except for the
START and STOP conditions.
SDA
S
T
S
A
R/W= “0”
T
R
O
T
P
S
Slave
Address
Sub
Address(n)
Data(n)
Data(n+1)
Data(n+x) P
A
A
A
A
A
A
C
C
C
C
C
C
K
K
K
K
K
K
Figure 11. Data Transfer Sequence at I²C Bus Mode
0
0
1
0
0 CAD1 CAD0 R/W
(CAD1-0 is set by the pin)
Figure 12. The First Byte
0
0
0
A4
A3
A2
A1
A0
Figure 13. The Second Byte
D7 D6 D5 D4 D3 D2 D1 D0
Figure 14. The Third Byte and After The Third Byte
015002776-E-00
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2015/03