6.18.2 Using parameters to call subroutine
Subroutine may contain the transfer parameters.The parameter is defined in the local
variable table of the subroutine.Parameters must have a symbol name (up to 23
characters), a variable type, and a data type.Each subroutine can be set up to 16
IN/OUT parameters.
Local variable table has 4 types of variables.They are IN, IN - OUT, OUT and TEMP.
Parameter type and description
Parameters are transferred to the subroutine.If the parameter is a
IN
direct address (e.g. VB10),the specified location value is transferred to the
subroutine.If the parameter is an indirect address (such as *AC1),the specified
location value is transferred to the subroutine.If the parameter is the data constant
(16#1234) or address (&VB100) ， constants or addresses are transferred to the
subroutine.
The specified location value is transferred to the subroutine.The
IN_OUT
result of subroutine operation is transferred to the specified same location .This
parameter does not allow to use constants (such as 16#1234) and addresses
(e.g.&VB100).
The result of subroutine operation is transferred to the specified
OUT
location.Constants (such as 16#1234) and addresses (e.g. &VB100) are not allowed to
be used as output.
Any local memory which is not used as a transfer parameter can’t be
TEMP
used for temporary storage in subroutine.
Parameter data type
Illustration
Boolean
It is used for unit input and output.
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