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12.SCRST - System Control and Reset

12.1.Overview

The reset logic manages the reset of the microcontroller. It issues a microcontroller reset, sets the device to its initial state and allows the reset source to be identified by software.

12.2.Features

Reset The Microcontroller to Initial State.

Multiple Reset Sources:

Power-on Reset

VCC Level Monitoring (VLM) Reset

External Reset

Watchdog System Reset

12.3.Resetting the AVR

During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset Vector. The instruction placed at the Reset Vector must be an Relative Jump instruction (RJMP) to the reset handling routine. If the program 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 the next shows the reset logic. Electrical parameters of the reset circuitry are defined in section System and Reset Characteristics.

Figure 12-1. Reset Logic

VLM

Power-on Reset

Circuit

Pull-up Resistor

SPIKE

FILTER

Watchdog

Oscillator

Clock

Generator

DATA BUS

Reset Flag Register

(RSTFLR)

PORF

EXTRF

WDRF

CK

Delay Counters

TIMEOUT

The I/O ports of the AVR are immediately reset to their initial state when a reset source goes active. This does not require any clock source to be running.

Atmel ATtiny102 / ATtiny104 [DATASHEET]

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Atmel-42505D-ATtiny102-ATtiny104_Datasheet_Complete-10/2016