ATEVK1105 Atmel, ATEVK1105 Datasheet - Page 95

• Manufacturer Part Number: ATEVK1105
• Description: KIT EVAL FOR AT32UC3A0
• Manufacturer: Atmel
• Series: AVR®32r
• Type: MCUr

Specifications of ATEVK1105

• Contents: Evaluation Board, Software and Documentation
• Processor To Be Evaluated: AT32UC3A0512
• Processor Series: AVR
• Data Bus Width: 32 bit
• Interface Type: USART, TWI, USB, SPI, Ethernet
• Operating Supply Voltage: 3.3 V
• Silicon Manufacturer: Atmel
• Core Architecture: AVR
• Core Sub-architecture: AVR UC3
• Silicon Core Number: AT32UC3A0512
• Silicon Family Name: AVR
• Kit Contents: Board CD Docs
• Rohs Compliant: Yes
• For Use With/related Products: AT32UC3A0
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

15.5
32058J–AVR32–04/11
Functional Description
The WDT is enabled by writing the EN bit in the CTRL register to one. This also enables the RC
clock for the prescaler. The PSEL bitfield in the same register selects the watchdog timeout
period:
The next timeout period will begin as soon as the watchdog reset has occured and count down
during the reset sequence. Care must be taken when selecting the PSEL value so that the time-
out period is greater than the startup time of the chip, otherwise a watchdog reset can reset the
chip before any code has been run.
To avoid accidental disabling of the watchdog, the CTRL register must be written twice, first with
the KEY field set to 0x55, then 0xAA without changing the other bitfields. Failure to do so will
cause the write operation to be ignored, and CTRL does not change value.
The CLR register must be written with any value with regular intervals shorter than the watchdog
timeout period. Otherwise, the device will receive a soft reset, and the code will start executing
from the boot vector.
When the WDT is enabled, it is not possible to enter Static mode. Attempting to do so will result
in entering Shutdown mode, leaving the WDT operational.
T
WDT
= 2
(PSEL+1)
/ f
RC
AT32UC3A
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