TOF 는 오프 딜레이 타이머을 말한다.
I:1/0 비트가 ON 되면 T4:0/EN 은 ON 되지만 T4:0/EN 은 I:1/0 비트가 OFF 되는
시점에서 ON 되고 8초가 지난후 T4:0/DN 비트는 OFF 된다.
이때 T4:0/EN 은 OFF 된다.
만일 T4:0/DN 이 OFF 되기 전에 다시 I:1/0 비트가 ON 되면 T4:0/DN 은 OFF 된다.
현재 진행중(ACC)인 타이머 데이터를 초기화(RESER-ZERO) 시킬 때에는
RES 명령어를 사용 하시면 됩니다.
[-원본글-]
Use the TOF instruction to turn an output on or off after its rung has been off for a preset time interval.
The TOF instruction begins to count timebase intervals when the rung makes a TRUE-to-FALSE
transition. As long as rung conditions remain FALSE, the timer increments its accumulated value
(ACC) each scan until it reaches the preset value (PRE). The accumulated value is reset when rung
conditions go TRUE regardless of whether the timer has timed out.
The TOF command is used as an output on a rung which, unlike the TON command, is only active
(counting) when the rung conditions are FALSE. The Enable bit work the same as the TON
command, the Enable bit is set only when the rung conditions are TRUE and remains set until the
rung goes FALSE. Although the Enable bit works the same way, don't forget that the counter works
opposite the TON, it counts when the Enable bit is OFF, and stops when the accumulated value is
reached or when the Enable bit is ON. The Done bit gets set when the rung conditions are TRUE and
remains ON until the Accumulated value equals or is greater than the Preset value (while rung
conditions are still FALSE).
There are four fields of the TOF command, the first being the address of the counter (Timer field), for
example T4:x (where x is the Timer number). Second is the Time Base, this is preset between two
values, 1.0 second or 0.01 second for counting. The third field, Preset is the time you want to count
(be sure to match the Preset time units with the Time Base time units). The last field is the
Accumulated value, this is the time that passed during the FALSE rung condition. Usually this is set
to 0, however it can be set to other values to increase, or reduce the time to reach the Preset value.
Because the Preset and Accumulator bits are addressable, the values can be changed within the
program (based on other rung instructions).
NOTE: The Reset (RES) instruction cannot be used with the TOF instruction because RES always
clears the status bits as well as the accumulated value.
Develop a ladder rung that will cause the Timer Off-Delay T4:0 to begin counting when the input I:1/0
goes FALSE. Have the counter count to 8 seconds with a Time Base of 0.01 seconds and an
Accumulator Value of 0.
In this example the input is an XIC instruction used to make the rung either TRUE or FALSE. When
this input I:1/0 is TRUE, the Enable (EN) bit of the timer is ON, but the Timer Timing (TT) and the
Done (DN) bits are OFF. As soon as I:1/0 goes FALSE, the Enable bit goes OFF, the Timer Timing bit
goes ON and the counter begins to accumulate until it reaches its Preset value (in this case 8
seconds) where the Done bit goes ON and Timer Timing bit goes OFF. The Accumulator value and
the Done bits reset when the rung goes TRUE again, even if the Accumulated value hasn't reached
the Preset value yet.
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