Rainbow Electronics ATmega3290P_V - Manual (Page 42)

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ATmega329/3290/649/6490
2552H–AVR–11/06
Figure 16. MCU Start-up, RESET Tied to V
CC
Figure 17. MCU Start-up, RESET Extended Externally
External Reset An External Reset is generated by a low level on the RESET pin. Reset pulses longer
than the minimum pulse width (see Table 16) 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
counter starts the MCU after the Time-out period – t
TOUT
– has expired.
Figure 18. External Reset During Operation
Brown-out Detection ATmega329/3290/649/6490 has an On-chip Brown-out Detection (BOD) circuit for mon-
itoring the V
CC
level during operation by comparing it to a fixed trigger level. The trigger
level for the BOD can be selected by the BODLEVEL Fuses. The trigger level has a hys-
V
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
CC
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
V
CC
CC