2 Instruction Descriptions
2-130
NJ-series Instructions Reference Manual (W502)
The timer is reset when timer input In changes to FALSE. Remaining time ET is set to set time PT, and
timer output Q changes to FALSE.
The timer starts when In changes to TRUE. The value of ET is timed down. When the value of ET
reaches 0, timer output Q changes to TRUE. ET is not timed down after that.
The timer is reset if In changes to FALSE after the timer starts but before ET reaches 0.
The data type of timer status TimerDat is structure _sTimer.
The following figure shows a programming example and timing chart when PT is UINT#10. Variable ghi
will change to TRUE 1,000 ms (1 s) after variable A changes to TRUE.
For more precise timing, use the TON instruction (page 2-116), which is set in increments of 100 nano-
seconds (ns). The TON instruction times in increments of 100 nanoseconds (ns) when the instruction is
executed, so it is more precise than the Timer instruction. However, the execution time of the Timer
instruction is shorter.
• Timing is performed at the beginning of the POU that contains this instruction. Therefore, the value of
ET will be the same regardless of where the instruction is executed in the POU.
• Q is updated when the instruction is executed. Therefore, Q does not change to TRUE precisely
when the time that is set with PT elapses after the timer starts. Q changes to TRUE the next time the
instruction is executed after the time that is set with PT elapses after the timer starts. The change in
Q can therefore occur with a delay of up to one task period.
• Although TimerDat is an in-out variable, it is not necessary to pass any values. Create a memory
area for the size of the _sTimer structure and pass it to the instruction.
• Do not change the contents of TimerDat.
• The timer starts as soon as operation starts if In is already TRUE.
• If the value of PT changes, the new value is used from the next time that the timer is reset. The value
is not updated while timing is in progress.
• If this instruction is in a master control region and the master control region is reset, the timer is reset.
ET is set to the value of PT and the value of Q changes to FALSE.
• If this instruction is not executed due to the execution of a jump instruction (e.g., the JMP instruction),
the value of ET is not updated. However, timing still continues. Therefore, ET is updated to the correct
value the next time the instruction is executed.
Additional Information
Precautions for Correct Use
def:=Timer(A, UINT#10, abc, ghi, jkl);
LD ST
abc abc
A
def
ghi
UINT#10
jkl
Timer
In
PT Q
TimerDat
ET
In=A
Q=ghi
TRUE
FALSE
TRUE
FALSE
ET=jkl
PT=UINT#10
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