
37
8126F–AVR–05/12
ATtiny13A
8.2.2
External Reset
An External Reset is generated by a low level on the RESET pin if enabled. Reset pulses longer
erate 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 8-4.
External Reset During Operation
8.2.3
Brown-out Detection
ATtiny13A has an On-chip Brown-out Detection (BOD) circuit for monitoring 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 hysteresis to ensure spike free Brown-out
Detection. The hysteresis on the detection level should be interpreted as V
BOT+ = VBOT + VHYST/2
and V
BOT- = VBOT - VHYST/2.
When the BOD is enabled, and V
CC decreases to a value below the trigger level (VBOT- in Figure CC increases above the
trigger level (V
out period t
TOUT has expired.
The BOD circuit will only detect a drop in V
CC if the voltage stays below the trigger level for lon-
ger than t
Figure 8-5.
Brown-out Reset During Operation
CC
VCC
RESET
TIME-OUT
INTERNAL
RESET
VBOT-
VBOT+
tTOUT