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Procedures Section 3-2
■ Method 2: Registering the Instance Name in the Global Symbol Table in
Advance and Then Selecting the Instance Name
If the instance name is registered in the global symbol table in advance, the
instance name can be selected from the global symbol table to create other
instances.
1,2,3... 1. Select a data type of Function block in the global symbol table, input the
instance name, and registered the instance.
2. Press the F Key in the Ladder Section Window. The Function Block Invo-
cation Dialog Box will be displayed.
3. Select the instance name that was previously registered from the pulldown
menu on the FB Instance Field. The instance will be created.
Restrictions
Observe the following restrictions when creating instances. Refer to 2-3
Restrictions on Function Blocks for details.
• No more than one function block can be created in each program circuit.
• The rung cannot be branched to the left of an instance.
• Instances cannot be connected directly to the left bus bar, i.e., an EN
must always be inserted.
Note If changes are made in the I/O variables in a variable table for a function block
definition, the bus bar to the left of all instances that have been created from
that function block definition will be displayed in red to indicate an error. When
this happens, select the function block, right-click, and select Update Invoca-
tion. The instance will be updated for any changes that have been made in
the function block definition and the red bus bar display indicating an error will
be cleared.
3-2-5 Setting Function Block Parameters Using the P Key
After an instance of a function block has been created, input parameters must
be set for input variables and output parameters must be set for output vari-
ables to enable external I/O.
• Values, addresses, and program symbols (global symbols and local sym-
bols) can be set in input parameters. (See note a.)
• Addresses and program symbols (global symbols and local symbols) can
be set in output parameters. (See note b.)
Note (a) The function block’s input variable data size and the program’s
symbol data size must match.
(b) The function block’s output variable data size and the program’s
symbol data size must match.
1,2,3... 1. Inputs are located on the left of the instance and outputs on the right. Place
the cursor where the parameter is to be set and press the P Key. (Alter-
nately, select Function Block Parameter from the Insert Menu.) The New
Parameter Dialog Box will be displayed as shown below.
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