15.6.2.4 Normal Mode
In Normal mode operation, the length of a time-out period is configured in
CONFIG.PER. The WDT is enabled by writing a '1
' to the Enable bit in the
Control register (CTRL.ENABLE). Once enabled, the WDT will issue a system Reset if a
time-out occurs. This can be prevented by clearing the WDT at any time during the time-out
period.
The WDT is cleared and a new WDT time-out period is started by writing 0xA5 to the Clear register (CLEAR). Writing any other value than 0xA5 to CLEAR will issue an immediate system Reset.
There are 12 possible WDT time-out (TOWDT) periods, selectable from 8ms to 16s.
By default, the early warning interrupt is disabled. If it is desired, the
Early Warning Interrupt Enable bit in the Interrupt Enable register (INTENSET.EW) must be
written to '1
'. The Early Warning Interrupt is disabled again by writing a
'1
' to the Early Warning Interrupt bit in the Interrupt Enable Clear
register (INTENCLR.EW). If the early warning interrupt is enabled, an interrupt is
generated prior to a WDT Time-out condition. In Normal mode, the Early Warning Offset bits
in the Early Warning Interrupt Control register, EWCTRL.EWOFFSET, define the time when the
early warning interrupt occurs. The Normal mode operation is illustrated in the figure
Normal mode operation.