attiny25v ATMEL Corporation, attiny25v Datasheet - Page 42

• Manufacturer Part Number: attiny25v
• Description: Microcontroller With 2/4/8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

8.2.1
8.2.2
42
ATtiny25/45/85
Power-on Reset
External Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level
is defined in
V
well as to detect a failure in supply voltage.
A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the
Power-on Reset threshold voltage invokes the delay counter, which determines how long the
device is kept in RESET after V
when V
Figure 8-2.
Figure 8-3.
An External Reset is generated by a low level on the RESET pin if enabled. Reset pulses longer
than the minimum pulse width (see
ate 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
edge, the delay counter starts the MCU after the Time-out period – t
CC
is below the detection level. The POR circuit can be used to trigger the Start-up Reset, as
INTERNAL
INTERNAL
TIME-OUT
TIME-OUT
CC
RESET
RESET
RESET
RESET
V
V
decreases below the detection level.
CC
CC
“System and Reset Characteristics” on page
MCU Start-up, RESET Tied to V
MCU Start-up, RESET Extended Externally
V
V
V
POT
POT
RST
CC
t
TOUT
rise. The RESET signal is activated again, without any delay,
“System and Reset Characteristics” on page
CC
V
RST
t
TOUT
170. The POR is activated whenever
TOUT
– has expired.
RST
– on its positive
170) will gener-
2586K–AVR–01/08