II CORE BLOCK: INITIAL RESET

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

 

 

 

 

 

3.0 V (VDD = 3.3 V)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

tSTA3 (OSC3 oscillation start time) or more

 

 

 

 

 

 

 

 

 

#RESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.5VDD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Power on

 

 

 

0.1VDD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3.2 Power-on Reset Timing

Maintain the #RESET pin at 0.1•VDD 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 0.5•VDD 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.

B-II-3-2

EPSON

S1C33L03 FUNCTION PART