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Chapter 12 Serial Interface 3
Operation
XII - 10
12-3 Operation
This LSI contains a serial interface 3 that can be used for both communication types of clock synchronous
and single master IIC.
12-3-1 Clock Synchronous Serial Interface
Activation Factor for Communication
Table 12-3-1 shows the activation factor for communication. At master communication, the transfer clock is
generated by setting data to the transmit/receive shift register SC3TRB, or by receiving start condition. The
input signal from the SBT3 pin is masked inside of serial interface to prevent errors by noise except during
communication. This mask is automatically released by setting data to SC3TRB (writing data to the
SC3TRB register), or by inputting start condition to the data input pin. Therefore, at slave, input the external
clock after setting data to SC3TRB, or by inputting start condition.
Table 12-3-1 Activation factor of Synchronous Serial Interface
Transfer Bit Count Setup
The transfer bit count can be selected from 1 bit to 8 bits. Set it by the SC3LNG 2 to 0 flag of the SC3MD0
register (at reset : 111). The SC3LNG2 to 0 flag holds the previous set values till it is set again.
The SBT3 pin is masked inside serial to prevent errors by noise. At slave, input clock to the
SBT3 pin after start condition is input or data is set to SC3TRB.
Start Condition Setup
Start condition can be selected if it is enabled or not. Set by the SC3STE flag of the SC3MD0 register.
When start condition is enabled. the transfer bit counter is cleared as start condition is input during
communication, and after that, the communication is automatically started again. Start condition is en-
abled as data line (the SBI3 pin (with 3 channels) or the SBO3 pin (with 2 channels)) is changed from "H"
to "L", when clock line (the SBT3 pin) is "H".
transmission reception
Set dummy data
Input start condition
Input clock
after dummy data is set
Input clock
after start condition is input
Activation factor
Input clock after
transmission data is set
Set transmission data
at slave
at master