Counters and Timers

Counters and timers are electronic components used to record either a digital count or the passage of time. In some components, the counter or timer may control some other electronic system, such as a power supply. Both counters and timers will usually have some form of numeric display.
A counter is a digital circuit that records the number of events (usually a rising edge) that occur on its input terminal. A counter will have a maximum allowable count, after which the count will roll over and begin again at zero. Some counters can be programmed to count down instead of up (default). A counter can be reset to zero by enabling its reset pin. The max counting speed of the counter determines how fast the input can toggle before the counter starts to miss input events.
Timers work in a fashion similar to counters. However, a timer contains a reference clock that is used to determine the passage of time. While the input pin is enabled on the timer, it will record the seconds that have elapsed. A timer also has a maximum time count that can be recorded before rolling over. There are still some analog timers in use, but most commercially available timers will be digital.