 The Timer On delay instruction is used to turn an output on or off after the time has been on for the preset time interval. The timer requires user input data that consists of a preset value and a timebase. Timebase of the timer instructions is expressed in seconds. Common timebase values include 0.01, 0.10, 1.0 and 10 seconds. Preset value is the time duration of the timer circuit. The preset value sets the time the timer will accumulate to. The accumulated value is the time incremented as the timer is timing. For timer instructions, three control bits are available for programming use. Timer enable bit status is true when the timer instruction is true. Timer timing bit status is true when the timer is timing and the accumulated value is changing. Timer done bit status is true when the accumulated value meets the preset value. The timer off delay instruction is used to turn an output on or off after the timer has been off for the preset time interval. Similar to the timer on delay, the timer off delay timer uses the same control bits, timebase and preset functions. The timer off delay sets the enable and done bits when input conditions are true. When the input conditions change to false in the timer off delay instruction, the timer timing bit goes true. As the accumulated value reaches the preset value, the done and timer timing bits turn off. Timer on and off delays reset when the run conditions change true or false depending on the timer type. For applications requiring the accumulated time to be retained if there were a system fault or the run condition goes false, a retentive timer on is used. The retentive timer on is enabled and begins timing when the input conditions are true. By changing the run condition to false in the retentive timer circuit, the accumulated value stops timing and retains the time recorded until the run condition goes true again. As the accumulated value reaches the preset value, the done bit goes true and enables the output. A programmed reset instruction with same address of the timer is used to reset the retentive timer's accumulated value.