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5.7 Port 4, 8, 9
Ports 4, 8 and 9 are input/output ports, and are also used for PPG output and general-
purpose prescaler output.
■ Functions of Port 4, 8, 9
The port has three registers per bit, namely DDR, PDR, and PFS, and port input/output setup and function
selection can be executed independently per bit. The peripheral function is selected for pins whose PFS is
"1", whereas the port function is selected for those whose PFS is "0". Pins whose DDR is "1" are set to
Output, whereas pins whose DDR is "0" are se 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 4, 8, 9
Figure 5.7-1 Block Diagram of Port 4, 8, 9
Pin
PDR
PFS
DDR
Data register read
Pin
PDR
DDR
Data register read
PFS
P46 to P40
P87 to P80
P94 to P91
P90
Peripheral output
Peripheral output
Peripheral input