Installation manual

Publication 1747-RM001G-EN-P - November 2008
2-10 Basic Instructions
Timer Off-delay (TOF)
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)
based on the timebase for 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.
Using Status Bits
When processor operation 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
On returning to the REM Run or REM Test mode, the following can happen.
(EN)
(DN)
TOF
TIMER OFF DELAY
Timer T4:1
Time Base 0.01
Preset 120
Accum 0
Output Instruction
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
5/04
SLC
5/05
• •••••
Table 2.6 Setting TOF 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
Table 2.7 Returning to REM Run or REM Test Mode
Condition Result
If the rung is true: TT bit is reset
DN bit remains set
EN bit is set
ACC value is reset.
If the rung is false: TT bit is reset
DN bit is reset
EN bit is reset
ACC value is set equal to the preset value.