4507_M Datasheet, PDF (154/216 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 4500 SERIES

4507 Group
APPLICATION
2.5 Reset
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
(1) Power-on reset
Reset can be performed automatically at power on (power-on re-set) by connecting a diode and a
capacitor to RESET pin. Connect RESET pin and the external circuit at the shortest distance.
VDD
RESET
pin
(Note 2)
(Note 1)
Pull-up transistor
Internal reset
signal
Watchdog timer
output
WEF
VDD
RESET pin voltage
Reset
state
Internal reset signal
Power-on
Reset released
Notes 1:
This symbol represents a parasitic diode.
2: Applied potential to RESET pin must be VDD or less.
Fig. 2.5.1 Structure of reset pin and its peripherals, and power-on reset operation
Reset input
1 machine cycle or more
On-chip oscillator (internal oscillator)
is counted 5359 times.
0.85VDD
RESET
0.3VDD
Program 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. 2.5.2 Oscillation stabilizing time after system is released from reset
Rev.2.01 Feb 04, 2005
REJ09B0195-0201
2-39