Atmel Xplained Pro Evaluation Kit ATSAMD20-XPRO ATSAMD20-XPRO Hoja De Datos
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ATSAMD20-XPRO
181
Atmel | SMART SAM D20 [DATASHEET]
Atmel-42129K–SAM-D20_datasheet–06/2014
Figure 17-2. Normal-Mode Operation
17.6.2.5 Window Mode
In window-mode operation, the WDT uses two different time-out periods, a closed window time-out period (TO
WDTW
) and
the normal, or open, time-out period (TO
WDT
). The closed window time-out period defines a duration from 8ms to 16s
where the WDT cannot be reset. If the WDT is cleared during this period, the WDT will issue a system reset. The normal
WDT time-out period, which is also from 8ms to 16s, defines the duration of the open period during which the WDT can
be cleared. The open period will always follow the closed period, and so the total duration of the time-out period is the
sum of the closed window and the open window time-out periods. The closed window is defined by the Window Period
bits in the Configuration register (CONFIG.WINDOW), and the open window is defined by the Period bits in the
Configuration register (CONFIG.PER).
WDT time-out period, which is also from 8ms to 16s, defines the duration of the open period during which the WDT can
be cleared. The open period will always follow the closed period, and so the total duration of the time-out period is the
sum of the closed window and the open window time-out periods. The closed window is defined by the Window Period
bits in the Configuration register (CONFIG.WINDOW), and the open window is defined by the Period bits in the
Configuration register (CONFIG.PER).
By default, the WDT issues a system reset upon a time-out and the Early Warning interrupt is disabled. If an Early
Warning interrupt is required, INTENCLR/SET.EW must be set. Writing a one to INTENSET.EW enables the interrupt,
and writing a one to INTENCLR.EW disables the interrupt. If the Early Warning interrupt is enabled in window mode, the
interrupt is generated at the start of the open window period.
Warning interrupt is required, INTENCLR/SET.EW must be set. Writing a one to INTENSET.EW enables the interrupt,
and writing a one to INTENCLR.EW disables the interrupt. If the Early Warning interrupt is enabled in window mode, the
interrupt is generated at the start of the open window period.
The window mode operation is illustrated in
.
Figure 17-3. Window-Mode Operation
t [ms]
WDT Count
5
10
15
20
25
30
35
PER[3:0]=1
Timely WDT Clear
TO
WDT
WDT Timeout
System Reset
EWOFFSET[3:0]=0
Early Warning Interrupt
t [ms]
WDT Count
5
10
15
20
25
30
35
WINDOW[3:0]=0
PER[3:0]=0
Timely WDT Clear
C
los
ed
TO
WDTW
O
pen
TO
WDT
Early WDT Clear
WDT Timeout
Early Warning Interrupt