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CHAPTER 4 I/O PORTS
4.4.2
Explanation of Operations of Port 4 Functions
This section describes the operation of port 4.
s Operation of Port 4
r 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 form 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 is.
The value state of the pin can be read by reading the PDR4 register.
r 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.
r 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.
r Operation in stop mode
When the pin state designating bit of the standby control register (STBC: SPL) is set to 1 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 PDR4 register in the bit position corresponding to the pin.
Input remains fixed to prevent leaks by input open.
Table 4.4-4 "Operating Modes of Pins of Port 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
SPL: Pin state designating bit of standby control register (STBC: SPL)
Hi-Z: High impedance