Rainbow Electronics ATmega103L - Manual (Page 28)

ATmega603/103
28
Figure 25. MCU Start-Up, RESET Controlled Externally
External Reset
An external reset is generated by a low level on the RESET pin. Reset pulses longer than 50 ns will generate a reset, even
if the clock is not running. Shorter pulses are not guaranteed to generate a reset. When the applied signal reaches the
Reset Threshold Voltage - V
RST
- on its positive edge, the delay timer starts the MCU after the Time-out period t
TOUT
has
expired.
Figure 26. External Reset During Operation
Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of 1 XTAL cycle duration. On the falling edge of this
pulse, the delay timer starts counting the Time-out period t
TOUT
. Refer to page 51 for details on operation of the Watchdog.
VCC
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
VCC
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
RST