AT90PWM216 datasheet(45/344 Pages) ATMEL

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AT90PWM216/316 [DATASHEET]

7710H–AVR–07/2013

8.8.2

Voltage Reference Characteristics

Note:

1. Values are guidelines only.

8.9

Watchdog Timer

AT90PWM216/316 has an Enhanced Watchdog Timer (WDT). The main features are:

• Clocked from separate On-chip Oscillator

• 3 Operating modes

–Interrupt

– System Reset

– Interrupt and System Reset

• Selectable Time-out period from 16ms to 8s

• Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode

Figure 8-7.

Watchdog Timer

The Watchdog Timer (WDT) is a timer counting cycles of a separate on-chip 128 kHz oscillator. The WDT gives an

interrupt or a system reset when the counter reaches a given time-out value. In normal operation mode, it is

required that the system uses the WDR - Watchdog Timer Reset - instruction to restart the counter before the time-

out value is reached. If the system doesn't restart the counter, an interrupt or system reset will be issued.

In Interrupt mode, the WDT gives an interrupt when the timer expires. This interrupt can be used to wake the

device from sleep-modes, and also as a general system timer. One example is to limit the maximum time allowed

for certain operations, giving an interrupt when the operation has run longer than expected. In System Reset mode,

the WDT gives a reset when the timer expires. This is typically used to prevent system hang-up in case of runaway

code. The third mode, Interrupt and System Reset mode, combines the other two modes by first giving an interrupt

Table 8-4.

Internal Voltage Reference Characteristics

(1)

Symbol

Parameter

Condition

Min.

Typ.

Max.

Units

VBG

Bandgap reference voltage

1.1

tBG

Bandgap reference start-up time

µs

IBG

Bandgap reference current consumption

µA

128 KHz

OSCILLATOR

MCU RESET

INTERRUPT

WDIE

WDIF

WDP3

AT90PWM216 Datasheet(PDF) 45 Page - ATMEL Corporation

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