UPD78F9234MC-5A4-A Datasheet, PDF (66/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 4 PORT FUNCTIONS
(3) External clock input
The P121 pin is used as the X1 pin to input an external clock, and therefore it cannot be used as an I/O port pin.
The P122 pin can be used as an I/O port pin.
The system clock oscillation is selected by the option byte. For details, refer to CHAPTER 18 OPTION BYTE.
Generation of reset signal sets port 12 to the input mode.
Figures 4-12 and 4-13 show the block diagrams of port 12.
WRPU
RD
Figure 4-12. Block Diagram of P120 and P123
PU12
PU120, PU123
VDD
P-ch
WRPORT
WRPM
P12
Output latch
(P120, P123)
PM12
PM120, PM123
PU12: Pull-up resistor option register 12
P12: Port register 12
PM12: Port mode register 12
RD: Read signal
WR××: Write signal
P120, P123
64
User’s Manual U17446EJ5V0UD