Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 110)

Preface MicroLogix 1000 Programmable Controllers User Manual
6–12
Timer Off-Delay (TOF)
Use the TOF instruction to delay turning on or off an output. 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 controller resets the
accumulated value when rung conditions go true regardless of whether the timer has
timed out.
Using Status Bits
This Bit Is Set When
And Remains Set Until One
of the Following
Timer Done Bit DN (bit 13) rung conditions are true rung conditions go false and
the accumulated value is
greater than or equal to the
preset value
Timer Timing Bit TT (bit 14) rung conditions are false and
the accumulated value is less
than the preset value rung conditions go true or
when the done bit is reset
Timer Enable Bit EN (bit 15) rung conditions are true rung conditions go false
When the controller changes from the REM Run or REM Test mode to the
REM Program mode, or user power is lost while a timer off-delay instruction is
timing but has not reached its preset value, the following occurs:
•
Timer Enable (EN) bit remains set.
•
Timer Timing (TT) bit remains set.
•
Timer Done (DN) bit remains set.
•
Accumulated value (ACC) remains the same.
Execution Times
(
µ
sec) when:
True False
39.42 31.65
(EN)
(DN)
TOF
TIMER OFF DELAY
Timer
Time Base
Preset
Accum