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A watchdog timer (WDT, or simply a watchdog), sometimes called a computer operating properly timer (COP timer), [1] is an electronic or software timer that is used to detect and recover from computer malfunctions. Watchdog timers are widely used in computers to facilitate automatic correction of temporary hardware faults, and to prevent errant ...
A typical kitchen timer. A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. An example of a simple timer is an hourglass. Commonly, a timer triggers an alarm when it ends. A timer can be implemented through hardware or software.
The timer may switch equipment on, off, or both, at a preset time or times, after a preset interval, or cyclically. A countdown time switch switches power, usually off, after a preset time. A cyclical timer switches equipment both on and off at preset times over a period, then repeats the cycle; the period is usually 24 hours or 7 days.
The 555 timer IC is an integrated circuit used in a variety of timer, delay, pulse generation, and oscillator applications. It is one of the most popular timing ICs due to its flexibility and price. It is one of the most popular timing ICs due to its flexibility and price.
Another important timing value for a flip-flop is the clock-to-output delay (common symbol in data sheets: t CO) or propagation delay (t P), which is the time a flip-flop takes to change its output after the clock edge. The time for a high-to-low transition (t PHL) is sometimes different from the time for a low-to-high transition (t PLH).
Time-delay relays can be constructed to delay armature motion on coil energization, de-energization, or both. Time-delay relay contacts must be specified not only as either normally open or normally closed, but whether the delay operates in the direction of closing or in the direction of opening. The following is a description of the four basic ...
Busy-waiting itself can be made much less wasteful by using a delay function (e.g., sleep()) found in most operating systems. This puts a thread to sleep for a specified time, during which the thread will waste no CPU time. If the loop is checking something simple then it will spend most of its time asleep and will waste very little CPU time.
Clock skew (sometimes called timing skew) is a phenomenon in synchronous digital circuit systems (such as computer systems) in which the same sourced clock signal arrives at different components at different times due to gate or, in more advanced semiconductor technology, wire signal propagation delay. The instantaneous difference between the ...