CHAPTER 14 RESET FUNCTION
User’s Manual U15109EJ3V0UD
484
14.2 Pin Operations
During the system reset period, almost all pins are set to high impedance (except for RESET, X2, XT2, CPUREG,
V
DD0
, V
DD1
, ADCV
DD
, ADCGND, PORTV
DD0
to PORTV
DD2
, PORTGND0, PORTGND1, GND0, GND1, GND2, and
V
PP
/IC).
Accordingly, if connected to an external memory device, be sure to attach a pull-up (or pull-down) resistor to each
pin. If such a resistor is not attached, these pins will be set to high impedance, which could damage the data in
memory devices. Likewise, make sure the pins are handled so as to prevent such effects at the signal outputs by on-
chip peripheral I/O functions and output ports.
Figure 14-1. System Reset Timing by RESET Signal Input
Hi-Z
Analog delay
Analog delay
Analog delay
Eliminated as noise
Internal system
reset signal
RESET
X1
Reset is accepted
Reset is canceled
13.1 ms (@20 MHz operation)
Oscillation stabilization time
Figure 14-2. System Reset Timing by Watchdog Timer Overflow
Hi-Z
Hi-Z
Normal
operation
Normal operation
(reset processing)
Reset period
(oscillation
stopped)
Oscillation
stabilization
time wait
X1
Internal
reset signal
Port pin
of I/O port
Watchdog
timer
overflow