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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
(5) Pin configuration
The configurations of the serial clock pin (SCL) and the serial data bus pin SDA0 (SDA1) are shown below.
(a) SCL
Serial clock I/O alternate-function pin.
<1> Master
N-ch open-drain output
<2> Slave
Schmitt input
(b) SDA0 (SDA1)
Serial data I/O alternate-function pin.
Uses N-ch open-drain output and Schmitt-input buffers for both master and slave devices.
Note that pull-up resistors are required to connect to both serial clock line and serial data bus line, because open-
drain buffers are used for the serial clock pin (SCL) and the serial data bus pin (SDA0 or SDA1) on the I2C bus.
Figure 13-43. Pin Configuration
Caution Because it is necessary to make an N-ch open-drain output high impedance while data is
being received, set bit 6 (BSYE) of serial bus interface control register 0 (SBIC0) to 1 in
advance and write FFH to serial I/O shift register 0 (SIO0).
When the wakeup function is used (when bit 5 (WUP) of serial the serial operating mode
register 0 (CSIM0) is set), do not write FFH to SIO0 before reception. The N-ch open-drain
output is always high impedance even if FFH is not written to SIO0.
(6) Address match detection method
In the I2C mode, the master can select a specific slave device by sending slave address data.
Address match detection is performed automatically by the slave device hardware. A slave device address
is compared with the slave address sent from the master device. If they match and the wakeup state (WUP)
bit is then 1, the interrupt request flag (CSIIF0) is set (it is also set when a stop condition is detected). When
using the wakeup function (WUP = 1), set SIC to 1.
Caution Whether a slave is selected or not depends on detection of match of the data (address)
received after the start condition.
To detect this match, an address match detection interrupt (INTCSI0) that occurs when WUP
= 1, is normally used. Therefore, to enable detection of whether a slave is selected or not,
be sure that WUP = 1.
VDD
SCL
SDA0 (SDA1)
Master device
Clock output
(Clock input)
Data output
Data input
Slave devices
(Clock output)
Clock input
Data output
Data input
SCL
SDA0 (SDA1)