Editing Watchdog timer (section)

===Enabling===
A watchdog timer is said to be ''enabled'' when operating and ''disabled'' when idle. Upon power-up, a watchdog may be unconditionally enabled or it may be initially disabled and require an external signal to enable it. In the latter case, the enabling signal may be automatically generated by hardware or it may be generated under software control.

<gallery class="center" mode="nolines" heights="220" widths="280" Caption="Watchdog state diagrams">
File:Watchdog timer state diagram with autostart.svg|Unconditionally enabled watchdog
File:Watchdog timer state diagram with enable.svg|Watchdog with ''enable'' input signal
</gallery>

When automatically generated, the enabling signal is typically derived from the computer reset signal. In some systems the reset signal is directly used to enable the watchdog. In others, the reset signal is delayed so that the watchdog will become enabled at some later time following the reset. This delay allows time for the computer to boot before the watchdog is enabled. Without this delay, the watchdog would timeout and invoke a subsequent reset before the computer can run its application software — the software which kicks the watchdog — and the system would become stuck in an endless cycle of incomplete reboots.