
CHAPTER 2 PIN FUNCTIONS
User’s Manual U13952EJ3V1UD
39
2.2.14 AVSS
This pin is the A/D converter ground potential pin. Always keep it at the same potential as the VSS0 pin (even when
the A/D converter is not used).
2.2.15 RESET
This pin inputs an active-low system reset signal.
2.2.16 X1, X2
These pins are used to connect a crystal resonator for main system clock oscillation.
To supply an external clock, input the clock to X1 and input the inverted signal to X2.
2.2.17 XT1, XT2
These pins are used to connect a crystal resonator for subsystem clock oscillation.
To supply an external clock, input the clock to XT1 and input the inverted signal to XT2.
2.2.18 VDD0, VDD1
VDD0 is the positive power supply pin for ports, while VDD1 is the positive power supply pin for other than ports.
2.2.19 VSS0, VSS1
VSS0 is the ground potential pin for ports, while the VSS1 is the ground potential pin for other than ports.
2.2.20 VPP (
PD78F9418A only)
A high voltage should be applied to this pin when the flash memory programming mode is set and when the
program is written or verified.
Handle the pins in either of the following ways.
Independently connect a 10 k pull-down resistor.
Switch this pin to be directly connected to the dedicated flash programmer in programming mode or to VSS0 or
VSS1 in normal operation mode using a jumper on the board.
If the wiring between the VPP pin and VSS0 or VSS1 pin is long, or external noise is superimposed on the VPP pin, the
user program may not run correctly.