Editing Watchdog timer (section)

===Restarting===
[[File:WatchdogWindow.png|thumb|300px|Some watchdog timers only allow kicks during a time window. Kicks occurring outside the window have no effect on the timer and may be treated as faults.]]
The act of restarting a watchdog timer is commonly referred to as ''kicking''{{efn|name=fn1|Various terms are used for the act of restarting a watchdog timer. Some (e.g. ''kick'', ''pet'', ''feed'', ''tickle'') draw a connection to [[guard dog]]s, whereas others (e.g. ''tag'', ''ping'', ''reset'') do not. This article uses ''kick'' for consistency.}} the watchdog.<ref name="ESD"/><ref name="SMSWT"/> In electronic watchdogs, kicking is typically done by writing to a watchdog control [[Memory-mapped I/O|port]] or by setting a particular bit in a [[hardware register|register]]. Alternatively, some tightly coupled{{efn|A ''tightly coupled'' watchdog timer is effectively a built-in extension of the processor and, as such, may be accessed by special [[machine language]] instructions which are specific to it.}} watchdog timers are kicked by executing a special [[machine language]] instruction. An example of this is the CLRWDT (clear watchdog timer) instruction found in the instruction set of some [[PIC microcontroller]]s.

In computers that are running [[operating system]]s, electronic watchdog restarts are usually invoked through a [[device driver]]. For example, in the [[Linux operating system]], a [[user space]] program will kick the watchdog by interacting with the watchdog device driver, typically by writing a zero character to {{mono|/dev/watchdog}} or by calling a KEEPALIVE [[ioctl]].<ref name="LinuxWatchdogApi"/> The device driver, which serves to abstract the watchdog hardware from user space programs, may also be used to configure the time-out period and start and stop the timer.

Some watchdog timers will only allow kicks during a specific time window. The window timing is usually relative to the previous kick or, if the watchdog has not yet been kicked, to the moment the watchdog was enabled. The window begins after a delay following the previous kick, and ends after a further delay. If the computer attempts to kick the watchdog before or after the window, the watchdog will not be restarted, and in some implementations this will be treated as a fault and trigger corrective action.<ref name="oracle"/>