
1.6 Reliability, Safety, and Security 51
watchdog timer rolls over, it generates a done signal that should be attached to
an error interrupt in the system. The system should be designed so that, when
running properly, it always resets the timer before it has a chance to roll over.
Thus, a done signal from the watchdog timer indicates that the system is some-
how operating improperly. The watchdog timer can be used to guard against a
wide variety of faults.
design diversity Design diversity is a design methodology intended to reduce the chance that
certain systematic errors creep into the design. When a design calls for several
instances of a given type ...