RL78/G15 CHAPTER 4 PORT FUNCTIONS
R01UH0959EJ0110 Rev.1.10 Page 99 of 765
Mar 7, 2023
4.2.4 Port 12
Port 12 is an I/O port with an output latch. Port 12 can be set to the input mode or output mode in 1-bit units using port
mode register 12 (PM12). When the P121
Note 1
, P122
Note 1
, and P125 pins are used as an input port, use of an on-chip
pull-up resistor can be specified in 1-bit units by pull-up resistor option register 12 (PU12) (the on-chip pull-up resistor is
always valid for P125 when RESET
¯¯¯¯¯¯
input is selected (PORTSELB = 1)).
This port can also be used for external interrupt request input, connecting resonator for main system clock, external clock
input for main system clock, reset input, serial interface data input, comparator output, and timer I/O. Reset signal
generation sets port 12 to input mode.
Note 1. For 16-pin and 20-pin products.
Caution Once the power is turned on, P125 functions as the RESET
¯¯¯¯¯¯
input. The PORTSELB bit of the option
byte (000C1H) defines whether this port operates as P125/INTP1/(VCOUT0)/(VCOUT1)/(SI01) or
RESET
¯¯¯¯¯¯
. When this pin is set to P125/INTP1/(VCOUT0)/(VCOUT1)/(SI01), do not input the low level to
this pin during a reset by the selectable power-on-reset (SPOR) circuit and during the period from
release from the reset by the SPOR circuit to the start of normal operation. If input of the low level
continues during this period, the chip will remain in the reset state in response to the external reset.
Accordingly, the on-chip pull-up resistor is enabled after power is turned on.
4.2.5 Port 13
P137 is an input-only port. This port can also be used for timer input and external interrupt request input.
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