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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
13.4.5
I2C bus mode operation
The I2C bus mode is provided for when communication operations are performed between a single master device
and multiple slave devices. This mode configures a serial bus that includes only a single master device, and is based
on the clocked serial I/O format with the addition of bus configuration functions, which allows the master device to
communicate with a number of (slave) devices using only two lines: a serial clock (SCL) line and a serial data bus
(SDA0 or SDA1) line.
Consequently, when the user plans to configure a serial bus which includes multiple
microcontrollers and peripheral devices, using this configuration results in reduction of the required number of port
pins and on-board wiring.
In the I2C bus specification, the master sends start condition, data, and stop condition signals to slave devices
via the serial data bus, while slave devices automatically detect and distinguish the type of signals using the signal
detection function incorporated as hardware. This simplifies I2C bus control sections in the application program.
An example of a serial bus configuration is shown in Figure 13-35. The system below is composed of CPUs and
peripheral ICs having serial interface hardware that complies with the I2C bus specification.
Note that pull-up resistors are required to connect to both serial clock line and serial data bus line, because N-
ch open-drain outputs are used for the serial clock pin (SCL) and the serial data bus pin (SDA0 or SDA1) on the I2C
bus.
The signals used in the I2C bus mode are described in Table 13-4.
Figure 13-35. Serial Bus Configuration Example Using I2C Bus
SCL
SDA0 (SDA1)
SCL
SDA0 (SDA1)
SCL
SDA0 (SDA1)
SCL
SDA
Slave IC
Slave CPU 2
Slave CPU 1
Master CPU
VDD
Serial clock
Serial data bus
VDD