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5.9 Port C, D
Ports C and D are input/output ports, and are also used as the PWM output, serial I/O,
and external interrupt.
■ Functions of Port C, D
The port has three registers per bit, namely, DDR, PDR, and PFS and input/output, setup and function
selection can be executed independently per bit. The peripheral function is selected for pin whose PFS is
"1", whereas the port function is selected for these whose PFS is "0".
The pins whose DDR is "1" are set to Output, whereas pins whose DDR is "0" are set to Input. The PFS is
cleared to "0" by reset, and the port function is selected. The PDR is undefined, and the DDR is cleared to
"0" and set to Input.
In terms of the DDR specification per bit, for output setup, the value written to the PDR is output to the pin,
and the PDR contents are read as the read value of the PDR in this case.
At the time of input setup, the pin will have high impedance status. At this time, the pin level is read from
the read value of the PDR.
■ Block Diagram of Port C, D
Figure 5.9-1 Block Diagram of Port C, D
Pin
Peripheral signal
Peripheral input
Peripheral input
Peripheral output
I/O control
PDR
DDR
Data register read
Pin
PDR
PFS
DDR
Data register read
PC1, PC0
PD5, PD4
PD2, PD1
PFS
PC7 to PC2
PD7, PD3
PD0