External Reset - Atmel ATtiny25 Manual

8.4

External Reset

7598H–AVR–07/09
Figure 8-2. MCU Start-up, RESET Tied to V
V
CCRR
V
CC
V
PORMA X
V
PORMIN
RESET
V
RST
TIME-OUT
INTERNAL
RESET
Figure 8-3. MCU Start-up, RESET Extended Externally
V
V
POT
CC
RESET
TIME-OUT
INTERNAL
RESET
Table 8-1. Power On Reset Specifications
Symbol Parameter
Power-on Reset Threshold Voltage (rising)
V
POT
Power-on Reset Threshold Voltage (falling)
VCC Max. start voltage to ensure internal
V
PORMAX
Power-on Reset signal
VCC Min. start voltage to ensure internal
V
PORMIN
Power-on Reset signal
V VCC Rise Rate to ensure Power-on Reset
CCRR
V RESET Pin Threshold Voltage
RST
Note: 1. Before rising the supply has to be between V
An External Reset is generated by a low level on the RESET pin if enabled. Reset pulses longer
than the minimum pulse width (see
ning. Shorter pulses are not guaranteed to generate a reset. When the applied signal reaches
the Reset Threshold Voltage – V
after the Time-out period – t
CC
t
TOUT
V
RST
t
TOUT
PORMIN
Table 8-1) will generate a reset, even if the clock is not run-
– on its positive edge, the delay counter starts the MCU
RST
– has expired.
TOUT
ATtiny25/45/85
Min Typ
1.1 1.4
(1)
0.8 1.3
-0.1
0.01
0.1 V
CC
and V to ensure Reset.
PORMAX
Max Units
1.7 V
1.6 V
0.4 V
V
V/ms
0.9V V
CC
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