AK09918 Datasheet, PDF (16/30 Pages) Asahi Kasei Microsystems – 3-axis Electronic Compass

[AK09918]
10. Serial Interface
10.1. I²C Bus Interface
The I²C bus interface of AK09918 supports the Standard mode (100 kHz max.) and the Fast mode (400 kHz
max.).
10.1.1. Data Transfer
To access AK09918 on the bus, generate a start condition first.
Next, transmit a one-byte slave address including a device address. At this time, AK09918 compares the
slave address with its own address. If these addresses match, AK09918 generates an acknowledgement, and
then executes READ or WRITE instruction. At the end of instruction execution, generate a stop condition.
10.1.1.1. Change of Data
A change of data on the SDA line must be made during “Low” period of the clock on the SCL line. When
the clock signal on the SCL line is “High”, the state of the SDA line must be stable. (Data on the SDA line
can be changed only when the clock signal on the SCL line is “Low”.)
During the SCL line is “High”, the state of data on the SDA line is changed only when a start condition or a
stop condition is generated.
SCL
SDA
DATA LINE
STABLE :
DATA VALID
CHANGE
OF DATA
ALLOWED
Figure 10.1. Data Change
10.1.1.2. Start/Stop Condition
If the SDA line is driven to “Low” from “High” when the SCL line is “High”, a start condition is generated.
Every instruction starts with a start condition.
If the SDA line is driven to “High” from “Low” when the SCL line is “High”, a stop condition is generated.
Every instruction stops with a stop condition.
SCL
SDA
START CONDITION
STOP CONDITION
Figure 10.2. Start and Stop Condition
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