[AK4685]
1-3. ACKNOWLEDGE
ACKNOWLEDGE is a software convention used to indicate successful data transfers. The transmitting device will
release the SDA line (HIGH) after transmitting eight bits. The receiver must pull down the SDA line during the
acknowledge clock pulse so that SDA remains stable “L” during “H” period of this clock pulse. The AK4685 will
generates an acknowledge after each byte has been received.
In read operation, the slave, the AK4685 will transmit eight bits of data, release the SDA line and monitor the line for an
acknowledge. If an acknowledge is detected and no STOP condition is generated by the master, the slave will continue to
transmit data. If an acknowledge is not detected, the slave will terminate further data transmissions and await STOP
condition.
Clock pulse
for acknowledge
SCL FROM
MASTER
1
8
9
DATA
OUTPUT BY
TRANSMITTER
not acknowledge
acknowledge
DATA
OUTPUT BY
RECEIVER
START
CONDITION
Figure 21. Acknowledge on the I2C-bus
1-4. FIRST BYTE
The first byte, which includes seven bits of slave address and one bit of R/W bit, is sent after START condition. If the
transmitted slave address matches an address for one of the device, the receiver who has been addressed pulls down the
SDA line.
The most significant seven bits of the slave address are fixed as “0010010”. The eighth bit (LSB) of the first byte (R/W
bit) defines whether a write or read condition which the master requests. “1” indicates that the read operation is to be
executed. “0” indicates that the write operation is to be executed.
0
0
1
0
0
1
0
R/W
Figure 22. The First Byte
MS1106-E-00
2009/08
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AKM [ ASAHI KASEI MICROSYSTEMS ]
