UPD78F9500MA-CAC-A Datasheet, PDF (62/342 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcontrollers

CHAPTER 4 PORT FUNCTIONS
<R> (2) μPD78F950x
Port 2 is a 4-bit I/O port with an output latch. Each bit of this port can be set to the input or output mode by using
port mode register 2 (PM2). When the P20 to P23 pins are used as an input port, an on-chip pull-up resistor can be
connected in 1-bit units by using pull-up resistor option register 2 (PU2).
This port can also be used for timer I/O, and external interrupt request input.
The P23 pin is also used as the EXCLK pin of the system clock oscillator. The functions of the EXCLK pin differs,
therefore, depending on the selected system clock oscillator. The following two system clock oscillators can be used.
<1>High-speed internal oscillator
The P23 pin can be used as I/O port pin.
<2>External clock input
The P23 pin is used as the EXCLK pin to input an external clock, and therefore it cannot be used as an I/O
port pin.
The system clock oscillation is selected by the option byte. For details, refer to CHAPTER 15 OPTION BYTE.
Reset signal generation sets port 2 to the input mode.
Figures 4-5 to 4-7 show the block diagrams of port 2.
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User’s Manual U18172EJ3V0UD