Rockwell Automation AutoMax Enhanced Ladder Language Reference Manual - Manual (Page 41)

3Ć1
3.0 Timer Instructions
Use the Timer instruction to enable and disable activities at preĆdefined times. For
example, set a timer to turn on a valve or shut off a furnace.
Choose from these timer instructions:
Use this instruction: To:
Retentive Timer On (RTO) track accumulated time
Timer Off Delay (TOF) stop an activity at a preset time interval
Timer On Delay (TON) start an activity at a preset time interval
Timer Pulse (TP) enable an output for a preset time interval
The timer instructions use the timer data type for the variable in the Name parameter.
The maximum time interval is 248.5 days (5965 hours). You can specify time in
increments of 0.01 seconds.
How Timer Instructions Operate
Once the instruction is enabled, the elapsed value is updated at the start of a program's
scan. For example, if a program is scheduled to run every second, the elapsed value
for a timer in that program is incremented by 100 each time the program runs. Although
the timer is specified in units of 0.01 seconds, the actual duration may be affected by
the program's scan time. For example, if the scan time is 0.1 seconds and you set a
timer to 0.01 seconds, the actual timer elapsed time will be 0.1seconds, because the
timer output will only be updated when the timer executes at 0.1 seconds intervals (the
program's scan time).
The T and Q outputs of the timer instructions do not change unless the timer instruction
is executed, even if the correct amount of time has elapsed.