RL78/G13 CHAPTER 4 PORT FUNCTIONS
R01UH0146EJ0100 Rev.1.00 234
Sep 22, 2011
4.2.13 Port 12
P120 and P125 to 127 are 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 used as an input port, use of an on-chip pull-up resistor can be specified
by pull-up resistor option register 12 (PU12).
P121 to P124 are 4-bit input only ports.
Input to the P120 pin can be specified as analog input or digital input in 1-bit units, using port mode control register 12
(PMC12).
This port can also be used for A/D converter analog input, connecting resonator for main system clock, connecting
resonator for subsystem clock, external clock input for main system clock, and external clock input for subsystem clock.
Reset signal generation sets P120 to analog input, and sets P121 to P127 to input mode.
Table 4-16. Settings of Registers When Using Port 12
Pin Name
Name I/O
PM12× PMC12× Alternate Function Setting
Remark
Input 1 0
×
P120
Output 0 0
×
P121 Input
− −
OSCSEL bit of CMC register = 0
or EXCLK bit = 1
P122 Input
− −
OSCSEL bit of CMC register = 0
P123 Input
− −
OSCSELS bit of CMC register = 0
or EXCLKS bit = 1
P124 Input
− −
OSCSELS bit of CMC register = 0
Input 1
− −
P125 to
P127
Output 0
Caution The function setting on P121 to P124 is available only once after the reset release. The port once set
for connection to an oscillator cannot be used as an input port unless the reset is performed.
Remark ×: don’t care
PM12×: Port mode register 12
PMC12×: Port mode control register 12
<R>
<R>
<R>
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