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CHAPTER 4 I/O PORTS
4.5.2
Explanation of Operations of Port 5 Functions
This section describes the operation of port 5.
s Operation of Port 5
r Operation in output port mode
When 1 is written for a bit of the DDR5 register, the bit corresponding to the pin of port 5, the pin
functions as an output port.
In output port mode, the output transistor operation is enabled and the output latch data is
output to the pin.
Once data has been written into the PDR5 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 PDR5 register.
r Operation in input port mode
When 0 is written for a bit of the DDR5 register, the bit corresponding to the pin of port 5, the pin
functions as an input port.
In input port mode, the output transistor is OFF and the pin state is Hi-Z.
Once data has been written into the PDR5 register, the written data is held in the output latch
but is not output to the pin.
The value state of the pin can be read by reading the PDR5 register.
r Operation in mode enabling the output from a peripheral
When the output enable bit for a peripheral is set enable, the corresponding pin is set to serve
the output from the peripheral.
Because the value state of the pin can be read from the PDR5 register even when the output
from the peripheral is enabled, the value output from the peripheral can be read.
r Operation in mode enabling the input to a peripheral
Set a bit of the DDR5 register to 0, the bit corresponding to the pin of port 5 assigned for the
input to the desired peripheral, then the pin functions as an input port.
Regardless whether the peripheral is using the input pin, the value state of the pin can be read
by reading the PDR5 register.
r Operation when a reset is performed
When the CPU is reset, the bits of the DDR5 register are initialized to 0. Thus, the output
transistor becomes OFF (input port mode) and the pin becomes Hi-Z.
However, CPU resets do not initialize the PDR5 register. If the pin is used as an output port
after the reset, reinitialize the PDR5 register to contain new output data in the bit position
corresponding to the pin and then set the corresponding bit of the DDR5 register so that the pin
will function as an output port.