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Chapter 12 Serial Interface 3
Operation
XII - 28
Start Condition Setup
At IIC communication, enable start condition by the SC3STE flag of the SC3MD0 register at the begin-
ning of communication. The SC3STE flag of the SC3MD0 register can select if start condition is enabled
or not.
If start condition is detected during data communication when the start condition is enabled, the SC3STC
flag of the SC3CTR register is set to "1", and the communication complete interrupt SC3IRQ is gener-
ated to finish the transmission. At this case, the communication is not normal so that something should
be done by the software, such a counter measure of stop condition, and the communication should be
started again.
The SC3STC flag should be cleared by the software.
Start condition is generated as data line (SDA pin) is changed from "H" to "L", when clock line (the SLC
pin) is "H".
Generation of Stop Condition
Stop condition is generated as the SDA line is changed from "L" to "H", when the SCL line is "H". Stop
condition can be generated by setting the IICBSY flag of the SC3CTR register to "0" by the software.
When the IICBSY flag is "0", use the program with data output function of a general port.
SDA
(Serial data)
SCL
(Serial clock)
Start condition Stop condition
Input Edge/Output Edge Setup
At IIC communication, data is always received at the falling edge of clock. Set the SC3CE1 flag of the
SC3MD0 register to "1", and select "falling" at the received data input edge. Even if the SC3CE1 flag is
set to "0", the received data is stored at the falling edge of clock, but any error is generated because IIC
clock line (SCL) becomes "H" after the communication of the last data.
Figure 12-3-12 Start Condition and Stop Condition
To detect start condition, set the SC3SBIS flag of the SC3MD1 register to "input serial data",
regardless of transmission/reception.
Data I/O Pin Setup
The SDA pin (for SBO3 pin, too) is used to input/output data. Set the SC3IOM flag of the SC3MD1
register to "1" to input serial data from the SBO3 pin. The SBI3 pin is not used, so it can be used as a
general port. But, always set the SC3SBIS flag of the above register to "1" to set "input serial data".
At IIC communication, set the SC3CE1 flag of the SC3MD0 register to "1" to select "falling"
of the received data input edge.