Rainbow-electronics ATtiny861_V Uživatelský manuál stáhnout pdf (Strana 40)

2588B–AVR–11/06

ATtiny261/461/861

9.0.3 Power-on Reset

A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level

is defined in ”System and Reset Characteristics” on page 189. The POR is activated whenever

is below the detection level. The POR circuit can be used to trigger the Start-up Reset, as

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

rise. The RESET signal is activated again, without any delay,

when V

decreases below the detection level.

Figure 9-2. MCU Start-up, RESET

Tied to V

Figure 9-3. MCU Start-up, RESET Extended Externally

9.0.4 External Reset

An External Reset is generated by a low level on the RESET

pin if enabled. Reset pulses longer

than the minimum pulse width (see ”System and Reset Characteristics” on page 189) will gener-

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

RST

– on its positive

edge, the delay counter starts the MCU after the Time-out period – t

TOUT

–

has expired.

RESET

TIME-OUT

INTERNAL

RESET

TOUT

POT

RST

RESET

TIME-OUT

INTERNAL

RESET

TOUT

POT

RST

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Rainbow-electronics ATtiny861_V Uživatelský manuál Strana 40