CHAPTER 17 SERIAL INTERFACE IIC0
Preliminary User’s Manual U17260EJ3V1UD
426
17.5 I
2
C Bus Definitions and Control Methods
The following section describes the I
2
C bus’s serial data communication format and the signals used by the I
2
C bus.
Figure 17-12 shows the transfer timing for the “start condition”, “address”, “data”, and “stop condition” output via the
I
2
C bus’s serial data bus.
Figure 17-12. I
2
C Bus Serial Data Transfer Timing
SCL0
SDA0
Start
condition
Address R/W
ACK
Data
1-7
8
9
1-8
ACK
Data
ACK
Stop
condition
9
1-8
9
The master device generates the start condition, slave address, and stop condition.
The acknowledge (ACK) can be generated by either the master or slave device (normally, it is output by the device
that receives 8-bit data).
The serial clock (SCL0) is continuously output by the master device. However, in the slave device, the SCL0’s low
level period can be extended and a wait can be inserted.
17.5.1 Start conditions
A start condition is met when the SCL0 pin is at high level and the SDA0 pin changes from high level to low level.
The start conditions for the SCL0 pin and SDA0 pin are signals that the master device generates to the slave device
when starting a serial transfer. When the device is used as a slave, start conditions can be detected.
Figure 17-13. Start Conditions
SCL0
SDA0
H
A start condition is output when bit 1 (STT0) of IIC control register 0 (IICC0) is set (to 1) after a stop condition has
been detected (SPD0: Bit 0 = 1 in IIC status register 0 (IICS0)). When a start condition is detected, bit 1 (STD0) of
IICS0 is set (to 1).