Campbell-scientific CR9000X Measurement and Control System Instrukcja Użytkownika Pobierz pdf (Strona 182)

Section 5. Program Declarations

SUB, EXIT SUB, END SUB

Declares the name, variables, and code that form a Subroutine.

Syntax

Sub SubName [(VariableList )]

[ statementblock ]

[ Exit Sub ]

[ statementblock ]

End Sub

A Subroutine is a separate procedure that is called by the main program using a

Call statement. A Subroutine can take arguments, perform a series of

statements, and change the value of its arguments. However, a Subroutine can't

be used in an expression. You can call a Subroutine using the name followed

by the variable list.

See the Call topic in Section 9.1 Program Structure/ Control for specific

information on how to call Subroutines.

Subroutines must be declared before they are called in the program. The code

for a Subroutine cannot be contained within the code for another Subroutine;

however, a Subroutine can be called by another Subroutine. If one Subroutine

calls another, the second Subroutine must be placed in the code before the

Subroutine that calls it. Subroutines cannot be used in an expression.

Because of how data is buffered in the task sequencer, a subroutine call should

be the last item in the main body of the program. Measurement instructions

should never follow a call to a subroutine; doing so could result in bad data.

The Scan/NextScan instruction loop can be used within a Subroutine using a

different execution interval than the main program.

Variables declared by Dim within a subroutine or function are local to that

subroutine or function. The same variable name can be used within other

subroutines or functions or as a global variable without conflict. Variables used

as parameters to a subroutine or function are also local.

When a Subroutine is called from the Main Program Scan, a skipped scan will

occur if there is not sufficient time for the Subroutine

measurements/processing in addition to the main scan's

measurement/processing time requirements.

Caution Subroutines can be recursive; that is, they can call themselves to perform a

given task. However, recursion can lead to strange results.

THE SUB STATEMENT HAS THESE PARTS:

Part Description

Sub Marks the beginning of a

Subroutine.

5-12

1 2 ... 177 178 179 180 181 182 183 184 185 186 187 ... 441 442

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