4513_03 Datasheet, PDF (159/210 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.7 Reset
2.7 Reset
System reset is performed by applying “L” level to the RESET pin for 1 machine cycle or more when the
following conditions are satisfied:
qthe value of supply voltage is the minimum value or more of the recommended operating conditions
qoscillation is stabilized.
Then when “H” level is applied to RESET pin, the software starts from address 0 in page 0 after elapsing
of the internal oscillation stabilizing time (f(XIN) is counted for 16892 to 16895 machine cycles). Figure 2.7.2
shows the oscillation stabilizing time.
2.7.1 Reset circuit
The 4513/4514 Group has the power-on reset circuit and voltage drop detection circuit.
(1) Power-on reset
Reset can be performed automatically at power on (power-on reset) by connecting resistors, a diode,
and a capacitor to RESET pin. Connect a capacitor between the RESET pin and VSS at the shortest
distance.
VD D
VDD
RESET pin voltage
RESET pin
(Note)
Internal reset signal
Voltage drop detection circuit
Watchdog timer output
WEF
Note:
This symbol represents a parasitic diode.
Applied potential to RESET pin must be VDD or less.
Fig. 2.7.1 Power-on reset circuit example
Power-on
Reset state
Internal reset signal
Reset released
Reset input
1 machine cycle or more
f(XIN) is counted 16892 to
16895 times.
0.85VDD
RESET
0.3VDD
Software starts
(address 0 in page 0)
(Note)
Note: Keep the value of supply voltage to the minimum value
or more of the recommended operating conditions.
Fig. 2.7.2 Oscillation stabilizing time after system is released from reset
2-56
4513/4514 Group User’s Manual