Editing Counter (digital) (section)

===One-shot timer===

The one-shot timer shown below uses a binary down-counter to generate an output pulse of precisely controlled duration. The timer output is the logical OR of all bits in the current count, and consequently the output pulse is active while the timer is running (I.e., when the count is not zero). When the count reaches zero, the output pulse is terminated and counting is halted.

[[File:One-shot timer.jpg|350px|border|Schematic diagram of a digital one-shot timer]]

To start the timer running, a value representing the desired pulse width is applied to the counter's Data inputs and Load is asserted. The pulse width is specified in terms of clock cycles. For example, in the case of a 1 MHz clock, a 100 microsecond output pulse has a duration of 100 clock cycles, as shown below:

[[File:One-shot timing diagram.jpg|350px|border|Timing diagram of a digital one-shot timer]]

This timer is ''retriggerable'', meaning that it can be restarted while running and thus stretch (extend the duration of) the output pulse.