4501 datasheet(155/212 Pages) RENESAS

155 / 212 page

2-38

Rev.2.01

Feb 07, 2005

4501 Group

APPLICATION

REJ09B0192-0201

2.5 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:

q the value of supply voltage is the minimum value or more of the recommended operating conditions

q oscillation 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 (On-chip oscillator (internal oscillator) clock is counted for 5359

times). Figure 2.5.2 shows the oscillation stabilizing time.

2.5.1 Reset circuit

The 4501 Group has the voltage drop detection circuit.

(1)

Power-on reset

Reset can be automatically performed at power on (power-on reset) by the built-in power-on reset

circuit. When the built-in power-on reset circuit is used, the time for the supply voltage to rise from

0 V to 2.0 V must be set to 100

µs or less. If the rising time exceeds 100 µs, connect a capacitor

between the RESET pin and VSS at the shortest distance, and input “L” level to RESET pin until the

value of supply voltage reaches the minimum operating voltage.

Fig. 2.5.1 Structure of reset pin and its peripherals, and power-on reset operation

Fig. 2.5.2 Oscillation stabilizing time after system is released from reset

2.5 Reset

RESET pin

WEF

Watchdog reset signal

(Note 1)

Pull-up transistor

(Note 1)

Power-on reset circuit

Volgate drop detection circuit

VDD (Note 3)

100

µs or less

(Note 2)

Internal reset signal

Power-on

Reset released

Internal reset signal

Reset

state

Notes 1:

This symbol represents a parasitic diode.

2: Applied potential to RESET pin must be VDD or less.

3: Keep the value of supply voltage to the minimum value

or more of the recommended operating conditions.

Power-on reset circuit output

RESET

0.3VDD

0.85VDD

(Note)

Note: Keep the value of supply voltage to the minimum value

or more of the recommended operating conditions.

Reset input

1 machine cycle or more

Program starts

(address 0 in page 0)

On-chip oscillator (internal oscillator)

counted 5359 times.

4501 Datasheet(PDF) 155 Page - Renesas Technology Corp

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