ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 54
ATMEGA644P-A15MZ
Manufacturer Part Number
ATMEGA644P-A15MZ
Description
MCU AVR 64KB FLASH 16MHZ 44QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644P-A15MZ
Package / Case
44-VQFN Exposed Pad
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
Operating Temperature
-40°C ~ 125°C
Speed
16MHz
Number Of I /o
32
Eeprom Size
2K x 8
Core Processor
AVR
Program Memory Type
FLASH
Ram Size
4K x 8
Program Memory Size
64KB (64K x 8)
Data Converters
A/D 8x10b
Oscillator Type
Internal
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Connectivity
I²C, SPI, UART/USART
Core Size
8-Bit
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
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Quantity
Price
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Manufacturer:
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Quantity:
3 500
Part Number:
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9.2
9.2.1
9.2.2
54
Watchdog Timer
ATmega164P/324P/644P
Features
Overview
•
•
•
•
ATmega164P/324P/644P has an Enhanced Watchdog Timer (WDT). The WDT is a timer count-
ing 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.
Figure 9-5.
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 16ms to 8s
Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode
– Interrupt
– System Reset
– Interrupt and System Reset
WATCHDOG
RESET
Watchdog Timer
OSCILLATOR
128kHz
WDIE
WDIF
WDE
WDP0
WDP1
WDP2
WDP3
MCU RESET
INTERRUPT
7674F–AVR–09/09
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