
II CORE BLOCK: INITIAL RESET
B-II-3-2
EPSON
S1C33L01 FUNCTION PART
Power-on Reset
Be sure to reset (cold start) the chip after turning on the power to start operating.
Since the #RESET pin is directly connected to an input gate, a power-on reset circuit should be configured outside
the chip.
An initial reset (#RESET = low) turns the high-speed (OSC3) oscillation circuit on. The CPU starts operating with
the OSC3 clock at the rising edge of the reset signal. The high-speed (OSC3) oscillation circuit takes time (10 ms
max. under the standard condition in 3.3 V) for the oscillation to stabilize,therefore initial reset must be released after
an appropriate oscillation-stabilization time has passed in order to start up the CPU without fault. The initial reset
pulse width must be exceeded the oscillation-stabilization time.
Figure 3.2 shows a power-on reset timing chart.
VDD
#RESET
tSTA3 (OSC3 oscillation start time) or more
3.0 V (VDD = 3.3 V)
0.5VDD
0.1VDD
Power on
Figure 3.2
Power-on Reset Timing
Maintain the #RESET pin at 0.1VDD or less (low level) after turning the power on until the supply voltage rises at
least to the oscillation start voltage (3.0 V). Furthermore, maintain the #RESET pin at 0.5VDD or less until the
high-speed (OSC3) oscillation circuit stabilizes oscillating.
Note: The OSC3 oscillation start time varies due to the elements used, board pattern and operating
environment, therefore allow enough margin for the reset-release time. Refer to "Oscillation
Characteristics", in which an example of oscillation start time is provided.
Reset Pulse
A low pulse can be input to the #RESET pin for resetting the chip being operated.
The minimum reset pulse width is provided in "AC Characteristics". Be sure to input a pulse that has a pulse width
longer than the minimum value.
To reset the chip when the high-speed (OSC3) oscillation circuit is in off status, the pulse width must be extended
until the oscillation stabilizes similarly to the power-on reset. Be aware that a short reset pulse may cause an
operation error.