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CHAPTER 4 I/O PORTS
● Operation when a reset is performed
When the CPU is reset, the bits of the DDR3 register are initialized to "0", at which time the output
transistors become OFF (input port mode) and the pins become Hi-Z.
However, CPU resets do not initialize the PDR3 register. If a pin is used as an output port after the reset,
reinitialize the PDR3 register to contain new output data in the bit position corresponding to the pin and
then set the corresponding bit of the DDR3 register so that the pin will function as an output port.
● Operation in stop mode
When the pin state setting bit of the standby control register (STBC: SPL) is set to "1" and when the stop
mode is entered, the pin becomes Hi-Z because the output transistor is turned OFF regardless of the value
existing on the DDR3 register in the bit position corresponding to the pin.
Table 4.3-4 summarizes the operating modes of the pins of port 3.
Note:
When the pull-up resistor is selected by using the pull-up setting register, the pin state will be "H" level
instead of Hi-Z in stop mode (SPL = 1). During a reset, however, the pull-up is invalid with the pin
remaining at Hi-Z.
Table 4.3-4 Operating Modes of Pins of Port 3
Pin name
Normal operation, sleep, stop
(SPL = 0)
Stop (SPL = 1) At a reset
P30/UCK/SCK
to
P33/EC, P37/BZ/PPG
General-purpose I/O port may also
serve I/O for peripherals
Hi-Z
Hi-Z
P34/TO/INT10
to
P36/INT12
General-purpose I/O port may also
serve outputs from peripherals and
external interrupt inputs
Hi-Z
(External interrupt input)
SPL : Pin state setting bit of standby control register (STBC: SPL)
Hi-Z: High impedance