Datasheet

78K0/Ix2 CHAPTER 4 PORT FUNCTIONS
R01UH0010EJ0500 Rev.5.00 131
Feb 28, 2012
4.2.6 Port 12
78K0/IY2 78K0/IA2 78K0/IB2
16 Pins 20 Pins 30 Pins/32 Pins
P121/X1/TOOLC0/<TI000>/<INTP0> P121/X1/TOOLC0/<TI000>/<INTP0> P121/X1/TOOLC0/<TI000>/<INTP0>
P122/X2/EXCLK/TOOLD0 P122/X2/EXCLK/TOOLD0 P122/X2/EXCLK/TOOLD0
P125/RESET/<TI000>/<INTP0> P125/RESET P125/RESET
Remark Functions in angle brackets < > can be assigned by setting the input switch control register (MUXSEL).
P121, P122, P125 function as an Input port.
When used as an input port only for P125, use of an on-chip pull-up resistor can be specified by pull-up resistor option
register 12 (PU12).
This port can also be used as pins for potential input for connecting resonator for main system clock, external clock
input for main system clock, external reset input, and clock input and data I/O for flash memory programmer/on-chip
debugger.
The timer input or external interrupt request input can be assigned to P121 of the 78K0/Ix2 and P125 of the 78K0/IY2
by setting the port alternate switch control register (MUXSEL).
Set bit 5 (RSTM) of the reset pin mode register (RSTMASK) to 1 when using P125/RESET as an input port, and clear
RSTM to 0 when using P125/RESET as an external reset input.
Reset signal generation sets port 12 to input mode.
Figures 4-23, 4-24 show block diagrams of port 12.
Cautions 1. When using the P121, P122 pins to connect a resonator for the main system clock (X1, X2), or to
input an external clock for the main system clock (EXCLK), the X1 oscillation mode, or external
clock input mode must be set by using the clock operation mode select register (OSCCTL) (for
details, refer to 5.3 (1) Clock operation mode select register (OSCCTL)). The reset value of
OSCCTL is 00H (all of the P121, P122 pins are Input port pins).
2. RESET/P125 is set in an external reset input after a reset release.
3. Because RESET/P125 immediately after release of reset is set in the external reset input, if a reset
signal is generated during low level input, the reset status continues until the input rises to the
high level.
Remark For how to connect a flash memory programmer using TOOLC0/X1, TOOLD0/X2, refer to CHAPTER 25
FLASH MEMORY. For how to connect TOOLC0/X1, TOOLD0/X2 and an on-chip debug emulator, refer to
CHAPTER 26 ON-CHIP DEBUG FUNCTION.