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4.13.2
Timer Function Blocks
Function
Function Block
Type
Off Delay Timer Built-in
(instance data is
WORD array)
See Built-In Timer
Function Blocks
below.
On Delay
Stopwatch
Timer
On Delay Timer
Timer Off Delay Standard
(instance data is a
structure variable)
See Standard Timer
Timer On Delay
Function Blocks.
Timer Pulse
Built-In Timer Function Blocks
Note: Special care must be taken when programming timers in program blocks that are not called
every sweep, and in parameterized blocks and UDFBs. For details, refer to:
Using OFDT, ONDTR and TMR in Program Blocks not Called Every Sweep
-
Timers that are Skipped by the Jump Instruction
-
Using OFDT, ONDTR and TMR in Parameterized Blocks, and
-
Using OFDT, ONDTR and TMR in UDFBs.
-
Data Required for Built-in Timer Function Blocks
The data associated with these functions is retentive through power cycles. Each timer uses a three-
word array of %R, %W, %P, %L or symbolic memory to store the following information:
GFK-2950C
Chapter 4. Ladder Diagram (LD) Programming
Mnemonic
Description
OFDT_HUNDS
The Current Value (CV) of the timer resets to zero
OFDT_SEC
when power flow input is on. CV increments while
OFDT_TENTHS
power flow is off. When CV=PV (Preset Value),
OFDT_THOUS
power flow is no longer passed to the right until
power flow input is on again.
ONDTR_HUNDS
Retentive on delay timer. Increments while it
ONDTR_SEC
receives power flow and holds its value when
ONDTR_TENTHS
power flow stops.
ONDTR_THOUS
TMR_HUNDS
Simple on delay timer. Increments while it
TMR_SEC
receives power flow and resets to zero when
TMR_TENTHS
power flow stops.
TMR_THOUS
TOF
When the input IN transitions from ON to OFF,
the timer starts timing until a specified period of
time has elapsed, then sets the output Q to OFF.
TON
When the input IN transitions from OFF to ON,
the timer starts timing until a specified period of
time has elapsed, then sets the output Q to ON.
TP
When the input IN transitions from OFF to ON,
the timer sets the output Q to ON for a specified
time interval.
Current value (CV) Word 1
Preset value (PV) Word 2
Control word
Word 3
February 2018
217
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