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Calls to Standard Function Blocks
Standard function blocks are instructions that have instance data in the form of a structure variable.
(For more information on function blocks and their instance data, refer to Functions and Function
Blocks in Chapter 2.) Standard function blocks are called in the same way that a UDFB is called.
PACSystems controllers support three standard function blocks:
Pulse timer
Generates output pulses of a given duration
(TP)
On-delay
Delays setting an output ON for a fixed period after an
timer (TON)
input is set ON.
Off-delay
Delays setting an output OFF for a fixed period after
timer (TOF)
an input goes OFF so that the output is held on for a
given period longer than the input.
Format of Calls to Standard Timer Function Blocks
Notes: TOF, TON and TP have the same input and output parameters, except for the instance
variable, which must be the same type as the instruction.
Writing or forcing values to the instance data elements IN, PT, Q, ET, ENO or TI may cause
erratic operation of the timer function block.
Instance data can be a variable or a parameter of the current UDFB or parameterized block.
Formal Convention
myTOF_Instance_Data(IN := inBool, PT := inDINT, ET => outDINT, Q => outBool, ENO =>
outBoolSuccess);
myTON_Instance_Data(IN := inBool, PT := inDINT, ET => outDINT, Q => outBool, ENO =>
outBoolSuccess);
myTP_Instance_Data(IN := inBool, PT := inDINT, ET => outDINT, Q => outBool, ENO =>
outBoolSuccess);
Note: ENO is an optional BOOL output parameter. If ENO is used in a statement that uses the
formal convention, the state of outBoolSuccess is set to 1 (call was successful) or 0 (call
failed).
Informal Convention
myTOF_Instance_Data(inBool, inDINT, outDINT, outBool);
myTON_Instance_Data(inBool, inDINT, outDINT, outBool);
myTP_Instance_Data(inBool, inDINT, outDINT, outBool);
Note: When using the informal convention, the operands must be assigned in the order shown
above (that is, IN, PT, ET, Q and ENO).
Block Types Supported for ST Calls
An ST block can call blocks of type Block, Parameterized Block, or user defined Function Block (UDFB)
or External Block (C block). For more information on block types, refer to Chapter 2.
GFK-2950C
Chapter 8. Structured Text (ST) Programming
February 2018
Refer to Timer Pulse in
Chapter 4
Refer to On Delay Timer
in Chapter 4
Refer to Off Delay Timer
in Chapter 4
371
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