ABB ST语言编程(11)

System 800xA Training

13.4Functions and Function Blocks

13.4.1Functions

Functions are called inside expressions with the following syntax:

Var := FunctionName(Parameter(s))

In the example below the square root of a flow signal is calculated by using the Sqrt()

function.

13.4.2FunctionBlocks

Function block calls do not appear in assignment statements. The call is itself a validstatement. Note that in ST, function block parameters are listedas follows:

:==>Input or Input/Output parameterOutput parameter

The example below shows

the code for calling a delay off timer:

The above timer function block is the same as the following in FBD form:

Function blocks aredeclared in a similar way to variables, by giving them a name (aninstance name). This name is then used to call them in the code.In the ST editor youmust declare function blocks explicitly in the“Function Block” declaration tab in the

editor by giving a name and a type:

Chapter13-11