ATtiny10/11/12
17
Reset Sources
The ATtiny10/11/12 provides three or four sources of reset:
• Power-on Reset. The MCU is reset when the supply voltage is below the power-on reset threshold (V
POT
).
• External Reset. The MCU is reset when a low level is present on the RESET pin for more than 50 ns.
• Watchdog Reset. The MCU is reset when the Watchdog timer period expires and the Watchdog is enabled.
• Brown-out Reset. The MCU is reset when the supply voltage V
CC
falls below a certain voltage (ATtiny12 only).
During reset, all I/O registers are then set to their initial values, and the program starts execution from address $000. The
instruction placed in address $000 must be an RJMP – relative jump – instruction to the reset handling routine. If the pro-
gram never enables an interrupt source, the interrupt vectors are not used, and regular program code can be placed at
these locations. The circuit diagram in Figure 16 shows the reset logic for the ATtiny10/11. Figure 17 shows the reset logic
for the ATtiny12. Table 6 defines the electrical parameters of the reset circuitry for ATtiny10/11. Table 8 shows the param-
eters of the reset circuitry for ATtiny12.
Figure 16. Reset Logic for the ATtiny10/11
Note:
1. The Power-on Reset will not work unless the supply voltage has been below V
POT
(falling).
Table 6. Reset Characteristics for the ATtiny10/11
Symbol
Parameter
Min
Typ
Max
Units
V
POT
Power-on Reset Threshold Voltage (rising)
1.0
1.4
1.8
V
Power-on Reset Threshold Voltage (falling)
0.4
0.6
0.8
V
V
RST
RESET Pin Threshold Voltage
0.6 V
CC
V
Power-on Reset
Circuit
Reset Circuit
Watchdog
Timer
On-chip
RC Oscillator
20-stage Ripple Counter
Q3
Q19
Q13
Q9
Q
Q
S
R
INTERNAL
RESET
POR
VCC
RESET
COUNTER RESET
FSTRT
CKSEL
