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CHAPTER 4 I/O PORTS
4.4.2 Operations of Port 4 Functions
This section describes the operation of port 4.
■ Operation of Port 4
● Operation in output port mode
When "1" is written for a bit of the DDR4 register, the bit corresponding to a pin of port 4, the pin functions
as an output port.
In output port mode, the output transistor operation is enabled and output latch data is output to the pin.
By setting the bit corresponding to the pin on the OUT4 register, N-ch open-drain or CMOS push-pull type
can be selected as the output format of the pin.
Once data has been written into the PDR4 register, the written data is held in the output latch and output to
the pin as it is.
The value state of the pin can be read by reading the PDR4 register.
● Analog input mode setting
Set a bit of the DDR4 register to "0", the bit corresponding to a pin of port 4 assigned for desired analog
input, so that its output transistor is set to OFF and the pin is set at Hi-Z.
Its output latch value can be read by reading the PDR4 register.
Set the bit of the ADEN register of the A/D converter to "1", the bit corresponding to the analog input pin
in use.
● Operation when a reset is performed
When the CPU is reset, the bits of the PDR4 register are initialized to "1". Thus, the output transistors
become OFF (input port mode) and the pins become Hi-Z.
● 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 DDR4 register in the bit position corresponding to the pin. Input remains fixed to prevent
leaks by input open.
Table 4.4-4 summarizes the operating modes of the pins of port 4.
Table 4.4-4 Operating Modes of Pins of Port 4
Pin name Normal operation, sleep, stop (SPL = 0) Stop (SPL = 1) At a reset
P40/AN0 to P43/AN3
General-purpose I/O port may also serve I/O
for peripherals
Hi-Z Hi-Z
SPL : Pin state setting bit of standby control register (STBC: SPL)
Hi-Z: High impedance