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The NET2000 variable object represents a PLC variable. A NET2000 variable object can be created at two different positions in the PVI object structure. If the variable object is created under a station object, then a global PLC variable is addressed. If the variable object is created under an NET2000 task object, then a local PLC variable (task variable) is addressed.

The name of the PLC variable must be specified in the connection description. These names are case sensitive.

NET2000 can only address variables up to 502 bytes in size.

The NET2000 line supports PLC event variables (see also the AT parameter). Monitoring for changes in the process data is already being carried out on the PLC. PVI Manager doesn't need to carry out any cyclic read requests. If the data in a PLC variables is not changed very often (at least not as often as the refresh time), then operating as a PLC event variable can reduce the data coming up in NET2000 communication. However, one disadvantage of this is an increased need for computing time on the PLC. It needs to be noted that specifying the refresh time (RF parameter) also has an effect on PLC event variables. Only single variables can be operated as PLC event variables.

Since NET2000 can only transfer data from PLC event variables with read or write requests, pay attention that at least one variable is read cyclically (polled) per station. A refresh rate should be defined for these variables which is less than or equal to the smallest PLC event variable refresh rate.

The data format of the variable object is given by the NET2000 line and corresponds to that of the PLC variable or an element of the PLC variable. An alignment of 2 is used for structure variables.

Connection description syntax:

Single variables, array variables, and structure variables:

/RO=<variable_name>

or

<variable_name>

Element of an array variable:

/RO=<variable_name>[<index>]

or

<variable_name>[<index>]

Element of a structure variable:

/RO=<variable_name>.<element_name>

or

<variable_name>.<element_name>

Dynamic variables must begin with the "*" character.

If the variable name is defined as the /RO parameter, the connection description must always be specified in quotation marks ("...") in the object description.

Connection description examples:

CD="/RO=TempValue"

Singe variable "TempValue" is addressed.

CD=TempField[2]

The 3rd element (index begins with 0) of an array variable is addressed.

CD=Vert.Stat.TempField[0]

The 1st element of an array variable inside the "Stat" structure and the "Vert" structure is addressed.

CD="*ViewBf"

Pointer to the dynamic variable "ViewBf" is addressed.

Example of object description:

AT=rwe CD="/RO=TempValue"

Single variable "TempValue" is addressed and operated as a PLC event variable.