Rockwell Automation Logix5000 Controllers Function Block Diagram Programming Manual - Manual (Page 11)

Program a Function Block Diagram Chapter 1
For a: Specify:
Element of a two dimension array tag_name[x,y]
Element of a three dimension array tag_name[x,y,z]
Element of an array within a structure tag_name.member_name[x]
Member of an element of an array tag_name[x,y,z].member_name
where:
x is the location of the element in the first dimension.
y is the location of the element in the second dimension.
z is the location of the element in the third dimension.
For a structure within a structure, add an additional member_name.
Define execution order (flow of data) by wiring elements together and indicating
any input (feedback) wires, if necessary. The location of a block does not affect the
order in which the blocks execute.
Data latching
If you use an IREF to specify input data for a function block instruction, the data
in that IREF is latched for the scan of the function block routine. The IREF
latches data from program-scoped and controller-scoped tags. The controller
updates all IREF data at the beginning of each scan as shown in this diagram.
Define the order of
execution
Rockwell Automation Publication 1756-PM009E-EN-P - October 2014 11