ATAVRSB202 Atmel, ATAVRSB202 Datasheet - Page 46

• Manufacturer Part Number: ATAVRSB202
• Description: KIT BATT MGMT FOR ATMEGA32HVB
• Manufacturer: Atmel

Specifications of ATAVRSB202

• Main Purpose: *
• Embedded: *
• Utilized Ic / Part: *
• Primary Attributes: *
• Secondary Attributes: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

11.4
11.4.1
11.4.2
8042B–AVR–06/10
Watchdog Timer
Features
Overview
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ATmega16HVB/32HVB has an Enhanced Watchdog Timer (WDT). The WDT counts cycles of
the Ultra Low Power RC 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.
Figure 11-6. Watchdog Timer
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 inter-
rupt and then switch to System Reset mode. This mode will for instance allow a safe shutdown
by saving critical parameters before a system reset.
The Watchdog always on (WDTON) fuse, if programmed, will force the Watchdog Timer to Sys-
tem Reset mode. With the fuse programmed the System Reset mode bit (WDE) and Interrupt
mode bit (WDIE) are locked to 1 and 0 respectively. To further ensure program security, altera-
tions to the Watchdog set-up must follow timed sequences. The sequence for clearing WDE and
changing time-out configuration is as follows:
Clocked from separate On-chip Oscillator
3 Operating modes
Selectable Time-out period from 16 ms to 8s
Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode
– Interrupt
– System Reset
– Interrupt and System Reset
Ultra Low Power RC
WATCHDOG
RESET
OSCILLATOR
WDIE
WDIF
WDE
ATmega16HVB/32HVB
WDP0
WDP1
WDP2
WDP3
MCU RESET
INTERRUPT
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