User’s Manual U11969EJ3V0UM00
243
CHAPTER 8 SERIAL INTERFACE FUNCTION
8.4.6 Definition and controls of I
2
C bus
The serial data communication format of I
2
C bus and the signals used are explained below.
Figure 8-14 shows each transfer timing of “start condition”, “data”, and “stop condition”, which are output onto the
serial data bus of I
2
C bus.
Figure 8-14. Serial Data Transfer Timing of I
2
C Bus
Start condition, slave address, and stop condition are output from the master.
The acknowledge signal (ACK) is output either from the master or the slave (normally, it is output from the reception
side of 8-bit data)
The serial clock (SCL) is kept being output from the master. However, the slave can extend the low level period
of SCL and insert wait.
(1) Start condition
The start condition is generated when the SDA pin changes from high level to low level while the SCL pin is
high level. The start condition of the SCL pin and the SDA pin is a signal which is the master outputs to the
slave when a serial transfer starts. The slave is provided with the hardware to detect the start condition.
Figure 8-15. Start Condition
Start condition is output by setting (1) the STT bit of the IICC register in the stop condition detection status
(the SPD bit of the IICS register = 1). When the start condition is detected, the STD bit of the IICS register
is set (1).
SCL
H
SDA
1 to 7
Address
R/W
Start
condition
1 to 7
8
9
8
9
SCL
SDA
1 to 7
8
9
ACK
Data
ACK
Data
Stop
condition
ACK
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